PT95482B - PROCESS FOR THE PREPARATION OF TETRATIOCARBONATE AQUEOUS SOLUTIONS - Google Patents

Abstract

Salts of tetrathiocarbonic acid are produced by a process in which a hydroxide (16), hydrogen sulfide (22), sulfur (12) and carbon disulfide (18) are reacted sequentially or continuously. The salts are produced as aqueous solutions having concentrations of about 15 to about 55 percent by weight.

Description

RESUME

The invention relates to the process for the preparation of aqueous solutions of salts of tetratiocarbonic acid, according to which a hydroxide is reacted with hydrogen sulfide, sulfur and carbon disulfide, sequentially or continuously. Salts are produced in the form of aqueous solutions having concentrations ranging from about 15 to about 55 weight percent.

Field of the Invention

The invention relates to the production of salts of tetratiocarbonic acid. In one of its most particular aspects, the invention relates to a process for the production of aqueous solutions of tetratiocarbonates, on a commercial scale.

BACKGROUND OF THE INVENTION

The chemistry of thiocarbonic acids and their salts has been studied in some detail, as indicated by O'Donoghue and Eahan, Journal of the Chemical Society, Vol. 89 (11), pages 1812-181 £ (1906); Yeoman, Journal of the Chemical Society, Vol. 119, pages 38-54 (1921); Mills and Robinson, Journal of the Chemical Society, Vol. 128 (ll), pages 2326-2332 (1928) and by Stone et al. in U.S. Patent 2,893,835, dated July 7, 1959.

According to O'Lonoghue and Kahan, Berzelius prepared about 1826 derivatives of thiocarbonic acid, reacting aqueous solutions of hydrosulfides with carbon disulfide, obtaining unstable solutions that contain unstable crystalline salts according to the following reaction:

KSH + CS ₂ -> K ₂ CS ₃ + H ₂ S (1)

Other thiocarbonates were prepared and characterized by O'Donoghue and Kahan. Its article, on page 1818, reports the formation of ammonium thiocarbonate by the reaction of liquid ammonia with cold alcoholic thiocarbonic acid, prepared by the dropwise addition of a solution of calcium thiocarbonate in concentrated hydrochloric acid, in order to produce thiocarbonic acid free (HgCS4), the calcium thiocarbonate used by the authors is described as a double salt, including the calcium cation in combination with the hydroxide and trithiocarbonate anions. In addition to thiocarbonic acid, other compounds prepared by O'Donoghue and Kahan. include the sodium, potassium, zinc and lead salts. However, in the preparation of any of these salts, a common feature was their relative instability, and the prepared salts could, in a matter of minutes, decompose releasing carbon disulfide, hydrogen sulphide and / or a metal sulphide.

This article by Yeoman reports further studies on thiocarbonates (called tritiocarbonates there) in addition to the preparation and properties of pertiocarbonates (or tetratiocarbonates), derived from tetratiocarbonic acid (H ₂ CS ^). Yeoman describes methods for preparing ammonium salts, alkali metals and alkaline earth metals from these acidic species. For example, Yeoman prepared ammonium trithiocarbonate by saturating an alcoholic solution of ammonia with hydrogen sulphide, then adding carbon disulfide to precipitate the produced salt. Ammonium pertechnocarbonate was prepared in a similar manner, except that after ammonia was reacted with hydrogen sulphide, elemental sulfur was added to form the disulfide, with the addition of carbon disulphide immediately precipitating the product,

Yeoman says that the solutions of trithiocarbonate and ammonium pertiocarbonate are very unstable, due to the decomposition to form thiocyanate as a product, and to the complete dissociation back into ammonium, hydrogen sulphide and carbon disulfide.

With regard to the stability of thiocarbonates, an important explanation is given, as exemplified by sodium trithiocarbonate and pertiocarbonate. Solutions of sodium trithiocarbonate in water are said to remain stable only with absolute excellence of oxygen and carbon dioxide; the presence of oxygen causes the decomposition to carbon disulfide and thiosulfates, while carbon dioxide decomposes the solution into carbonate, elemental sulfur, carbon disulfide and hydrogen sulphide. According to Yeoman, potassium trithiocarbonate behaves similarly.

Yeoman also tried to prepare and characterize the stability of thiocarbonate salts of four of the alkaline earth metals, 'feoman was unable to prepare a pure calcium tri- or tetrathiocarbonate, but noted that the double calcium trithiocarbonate salt he prepared, was more stable (probably because it was less hygroscopic) than sodium or potassium thiocarbonates. The barium salt of tetratiocarbonic acid cannot be isolated, although Yeoman believed that it existed in solution. Solid barium trithiocarbonate cannot be isolated, although it has been said to behave like trithiocarbon.

sodium bonate, when dissolved in water. The preparation of aqueous solutions of magnesium and strontium tri- and tetratiocarbonates has been claimed, but magnesium thiocarbonates have not been isolated.

The above-mentioned article by Mills and Kobinson shows the preparation of ammonium thiocarbonate by digesting ammonium pentasulfide (obtained by suspending sulfur in aqueous ammonia which is then saturated with hydrogen sulphide) with carbon disulfide. A crystalline residue from the reaction was found to be ammonium pertiocarbonate. However, the authors prepared a better ammonium pertiocarbonate ”by extracting ammonium pentasulfide with carbon disulfide in a Soxliet apparatus.

Stone et al. have shown various methods of preparing solid, tri- and tetraperoxythiocarbonates salts of alkali and alkaline earth metals, hereinafter referred to simply as tetrathiocarbonates. One of these methods involves the solution of an active metal, such as solid, in anhydrous ethanol, forming an ethoxide which, in turn, reacts with hydrogen sulphide and carbon disulfide to form sodium trithiocarbonate. They said, however, that trithiocarbonates tended to be quite soluble in ethanol, and that if one wanted to recover the solid material from the solution, it was necessary to treat the reactive mixture with a displacing agent, such as ether, in which case the thiocarbonates usually separate themselves, not as solids, but as oils that are difficult to crystallize which appear to be aqueous saturated solutions of the trithiocarbonate salt. Consequently, such a process is not considered feasible on a commercial scale. Similar problems are reported with tetrathiocarbonates salts, which were prepared using processes analogous to those of trithiocarbonates.

These problems were solved by carrying out the reaction of

preparation in a medium composed mostly of a non-solvent of the reaction components, and a small part of liquid miscible with the non-solvent and which is a measurable solvent of inorganic sulfides. The preferred non-solvents used were low boiling hydrocarbons, such as hexane, cyclohexane and benzene. The second solvent was preferably ethanol, isopropanol or dioxane.

The basic Chemical and Eisic properties of these materials as well as a number of methods for preparing them are summarized in considerable detail, starting on page 154, in Carbon sulphides and their inorganic and complex Chemistry ”by G. Gattow and W. Behrendt, Volume 2 of Topics in Sulfur Chemistry ”, A. Senning, Editor, George Thieme Publishers, Stuttgart, 1977.

What is needed is a process for the production of salts of tetratiocarbonic acid that is less laborious than the processes previously used. Such a process must be capable of producing aqueous solutions of tetrathiocarbons on a commercial scale. The present invention provides that process.

SUMMARY OF IHVEUQÃO

The present invention provides a process for the production of salts of tetratiocarbonic acid, capable of providing aqueous solutions of tetratiocarbonates in concentrations useful for various commercial applications, such as the control of nematodes or other pathogenic organisms in soil or water.

Although sulfuric acid and carbon disulfide could be expected to react to form trithiocarbonic acid

according to the following reaction:

H ₂ S + CS ₂ => H ₂ CS ₃ (2) this does not occur. The present invention provides a method less laborious than the previous ones and which can be readily performed in a simple and direct way.

According to one of the processes of the present invention, it has been found that tetratiocarbonates can be produced in concentrations above 30% in water, by means of a global process in which, for example, sodium hydroxide reacts with hydrogen sulphide to produce sulfide sodium, in an exothermic reaction; the sodium sulfide thus produced reacts with elemental sulfur in an endothermic reaction producing sodium disulfide; in turn, the sodium disulfide thus produced reacts with the carbon disulfide to produce sodium tetrathiocarbonate in an exothermic reaction. The reactive sequence is as follows:

NaOH + H ₂ S => Na ₂ S + 2 Η _£ 0 (3)

Ka ₂ S + S => Na ₂ S ₂ (4)

Iia ₂ S ₂ + CS ₂ => Ka ₂ CS ₄ (5)

Adding the reagents from reactions (3), (4) and (5) sequentially, under controlled conditions, results in a product comprising aqueous solutions of tetratiocarbonates in concentrations above 30 weight percent.

According to another of the processes of this invention, aqueous solutions of tetratiocarbonates can be produced in a process

they are continuous, in relatively high concentrations, such as about 30% by weight or more, through continuous feeding with water, a hydroxide, sulfur, carbon disulfide and hydrogen sulphide; continuously reacting the hydroxide, sulfur, carbon disulfide and hydrochloric acid; and continuously recovering an aqueous solution of a salt of tetratiocarbonic acid.

The reactions that occur simultaneously in a continuous process for the production of sodium tetratiocarbonate are as follows:

2Ea0H + H ₂ s = Na ₂ S + 2 H ₂ 0 (3) ^Ha 2 ^{S +} s = Ka ₂ S ₂ (4) HagSg + CS ₂ = Ua ₂ 0S ₄ (5) Ua ₂ S + CS ₂ = BFa ₂ 0S, (Θ ha ₂ CS2 + s = In ₂ CS ^ (7)

Adding water, sodium hydroxide, molten sulfur, carbon disulfide and hydrogen sulphide, simultaneously but separately, to a reactor and allowing it to react continuously under controlled conditions, results in a product comprising an aqueous solution with a sodium tetratiocarbonate concentration of 30 or more percent by weight. These tetratiocarbonate solutions are stable and directly toxic to many plant pathogenic organisms, as they decompose in the soil releasing carbon disulfide, which acts as a fumigant. Tetratiocarbonates are biodegradable, producing sulfates and carbonates, and do not leave residues on the soil or on the plants that have been treated with them.

BRIEF DESCRIPTION OF THE DRAWING

The only figure in the drawing is a schematic representation of a flow chart, in partial elevation, showing a system for carrying out the continuous process of the present invention, including a reactor tank with continuous agitation and its auxiliary equipment.

GLOBAL PROCESS

In the glohal process of the present invention, a hydroxide, sulfuric acid, sulfur and carbon disulfide react in approximately stoichiometric amounts in an aqueous medium producing aqueous solutions of tetratiocarbonate, with concentrations of 30 or more percent by weight, generally between 31 and 35 percent by weight .

The description of the invention will proceed using sodium tetrathiocarbonate as an example of the tetrathiocarbonates to which this invention is directed. It should be made clear, however, that other tetrathiocarbonates such as potassium tetrathiocarbonate, ammonium tetrathiocarbonate, lithium tetrathiocarbonate, calcium tetrathiocarbonate and magnesium tetrathiocarbonate can similarly be prepared using the respective hydroxides.

The process can be carried out in any suitable reactor in which the reagents can be mixed well and can be cooled or heated to control the reaction temperature. Pressure is not an important requirement, as pressures in the range of about 1 are sufficient for the process. at 2 kg / cm. Heating and cooling can be carried out by

External or internal heat exchangers. A stirred tank reactor, for example, is satisfactory to carry out the process of the present invention.

To ensure that the reactive pathway followed in the overall process of the present invention is the desired pathway, illustrated in reactions (3), (4) and (5), it is essential that the reagents are introduced into the reactor in due order, in the appropriate quantities and at the optimum temperature for the reactions to proceed as desired. The following description of a typical reaction run defines the reaction conditions and other factors that are important in obtaining the desired results.

A 23,000 liter tank reactor with stirrer is filled with nitrogen to form an essentially oxygen-free inert atmosphere. The oxygen level is usually less than 1.0 weight percent and preferably less than 0.3 weight percent. Water is then added to the reactor at a rate of 13500 kg / hr, over a period of 46 minutes. Sodium hydroxide is added to the reactor in an excess of 5 to 15 percent, preferably 10 percent in excess. The sodium hydroxide is added as a 50 weight percent solution, at a rate of 10 200 kg / hr. for a period of 43 minutes in the first stage of the process This results in a concentration of about 26 weight percent. Concentrations of about 10 to 50 percent can be used, but about 15 to 35 percent by weight should be used. The sodium hydroxide solution is preferably introduced into the reactor above the surface of the liquid. During this time the temperature rises about 22-0.

In the second phase of the process, which is exothermic, ahydrous acid is added to the sodium hydroxide solution at a rate of 726 kg / hr, for about 2 hours, providing an excess of not more than 5 percent. 0 hydrogen sulphide, which is added

As a gas, it is preferably introduced as close as possible (to the bottom of the reactor, to enable the upper hydrostatic layer of the reactor content and agitation to be effective in reacting the hydrogen sulphide with the hydroxide of

I 'sodium (reaction 3). An excess of hydrogen sulphide above the 5 percent mentioned above should be avoided as this excess of hydrogen sulphide can eventually cause an increase in pressure in the reactor. Typically, hydrogen sulphide gas can contain up to about 1-2 weight percent of inert gases, which simply cause a pressure increase and can be removed by ventilation. A continuous flow of about 7.3-15 kg / hr. for an external gas scrubber, for example, it is sufficient to drag inert gases and relieve pressure build-up. Alternatively, the pressure increase due to inert gases can be relieved by ventilation at the end of the addition of hydrogen sulphide. As stated above, the reaction between sodium hydroxide and hydrogen sulphide is exothermic. As a result the temperature rises by about 20 ° C,

Since sodium sulphide, which is formed by adding hydrogen sulphide to the diluted sodium hydroxide solution in the second stage of the process, begins to precipitate at temperatures below 32 ⁹ C, the reactor must be kept at least 43 ² C. Pressures greater than atmospheric from 0.175 to 0.7 kg / cm are suitable. The heat produced when mixing the sodium hydroxide solution with water and the exothermic reaction with the hydrogen sulphide is generally sufficient to prevent precipitation of the sodium sulphide. However, if the reactor temperature after adding hydrogen sulphide to the sodium hydroxide solution is insufficient to keep the sodium sulfide in solution, heat can be added to the reactor through a heater or a steam jacket to maintain the temperature at about 43 ^and 0. Agitation of the reagents is essential during this and the following phases.

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To start the third phase of the process, adding sulfur, the temperature must be above 60 ² C to ensure the reaction of the sulfur with the sodium sulfide. Temperatures in the range of 60 to 76.5 are desirable. 0 is added molten sulfur at a temperature of about 138 C ^2, preferably by spraying steam above the liquid phase of the reactor. The particle size of the sprayed sulfur should preferably be less than 3 nm in diameter. Ξ the contact between the molten sulfur droplets and the interior metal surfaces of the reactor should be for about 2 hours. The reaction of sulfur with sodium sulfide (Reaction 4) is endothermic, resulting in a temperature drop of about 30 ² C $ essential that there is no unreacted sulfur upon addition of carbon disulfide in the fourth stage of the process . Since the sulfur is extremely soluble in carbon disulfide, all unreacted sulfur would pass to the carbon disulfide phase instead of being available for the reaction with sodium sulfide according to reaction 4, thus decreasing the yield of product.

For the reaction between sodium disulfide and carbon disulfide (Reaction 5) runs at a reasonable rate, the optimal temperature was found 57 can be used to temperatures about 50 to 70 ² C. A typical pressure reactor is about 0.35 to 1.4 kg / cm2, preferably 0.7 to 1.05 kg / cm2. The carbon disulfide is added under the surface of the reactor liquids at a rate of 1271 kg / hr. for 2.5 hours. The temperature can be maintained at about 57 to 60 ² C, with cooling if necessary, as the reaction is exothermic. Ventilation is undesirable as carbon disulfide must be prevented from leaving the reactor to ensure optimum sodium tetrathiocarbonate yield. Consequently, agitation and recirculation of the resulting solution must continue until all carbon disulfide has

reacted, ο it may take a few hours. During the reaction to p

pressure can increase from 10.7 to about 1.4 kg / cm.

resulting product and an absolutely clear solution, containing neither unreacted sulfur, which would say an opaque product, nor unreacted carbon disulfide, which would appear as a separate phase or emulsion. The product is orange-red in color and has a slight sulfur odor. The specific quantities described above produced 19000 liters of sodium tetratiocarbonate at 31.8 weight percent in water, with a density of 1.20 to 1.30, typically 1.26 to 21 ² C, the small excess of sodium hydroxide and hydrogen sulphide used in the process The present invention proved to be suitable to help keep the active component, carbon disulfide, better in solution, thus reducing odor and stabilizing the product.

Thus, an overall process for producing salts of tetratiocarbonic acid has been presented as aqueous solutions with concentrations in the range 30-35 weight percent, which are relatively stable, although capable of releasing carbon disulfide under certain conditions.

CONTINUOS PROCESS

In the continuous process of the present invention, a hydroxide, sulfuric acid, sulfur and carbon disulfide continuously react in approximately stoichiometric amounts, in an aqueous medium, to produce solutions of tetratiocarbonates with concentrations of 15 weight percent or more, or preferably concentrations of 30 to 55 percent, or rather 40 to 50 weight percent of the tetrathiocarbonate salt. The concentrations .4

taller ones are particularly desirable as they enable greater production and lower transport costs. Although the reagents are typically present in stoichiometric amounts, an excess of about 5 to 10 weight percent of hydroxide and hydrogen sulfide has proven to be desirable to stabilize tetrathiocarbonate solutions. Especially preferred are an excess of about 10 percent hydroxide and 5 percent hydrogen sulfide.

The description of the invention will continue using sodium tetrathiocarbonate as an example of the tetrathiocarbonates to which this invention is directed. It should be noted, however, that other tetrathiocarbonates, such as potassium tetrathiocarbonate, ammonium tetrathiocarbonate, lithium tetrathiocarbonate, calcium tetrathiocarbonate and magnesium tetrathiocarbonate can be similarly prepared using the corresponding hydroxide.

The process can be carried out in any suitable reactor in which the reagents can be introduced simultaneously and continuously and mixed well, and in which the reaction temperature can be maintained as desired. Temperature control can be done by both external and internal heat exchangers. Pressure is not an important factor. Pressures higher than atmospheric are typically used, in the range of 0.35 to 2.1 kg / cm. A tank-type reactor with continuous agitation (CSTR), for example, is suitable for carrying out the process of the present invention.

continuous process for the production of sodium tetrathiocarbonate requires that all chemical reagents react completely to ensure that the reactions represented by equations (3), (4), (5), (6) and (7) are able to produce the product and avoid serious operational problems. If, for example, the sulfur does not react completely, it will become solid and will clog the filters and ducts of the products. If CS ₂ does not react completely, it will vaporize and the reactor pressure will increase significantly. Or worse, it will compete with Na ₂ S and Na ^ OS ^ for sulfur, giving rise to an 'incomplete reaction and obstructing pipelines and equipment.

In a continuous process, all possible reaction pathways are in competition. The dominate route has the fastest global kinetics. It can be determined, to a certain extent, which will be the dominant route for choosing reaction conditions, such as temperature, concentration and residence time.

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I 'Low temperatures and low concentrations, for example, the predominant reactive pathway is the path defined by reactions (3), (6) and (7) and at high temperatures the predominant reactive pathway is the path defined by reactions ( 3), (4) and (5).

The reaction (3), common to two pathways, is an ionic reaction and is very fast. This reaction, which is the fastest of the entire sequence of reactions, is instantaneous and complete.

If the temperature and product concentration are low, the reaction of CS ₂ with Na ₂ S (reaction 6) and the reaction of GSg with Na ₂ S ₂ (reaction 5) have the reaction rates immediately higher. The rate of reaction 5 is limited by mass transfer and depends on the concentration of CS ₂ in the aqueous phase, in which the reaction takes place. This reaction is slower at high temperatures because the solubility of CS ₂ in water as the temperature increases, decreases. The reaction of Na ₂ S with CS ₂ (reaction 6) is einetically limited to low temperatures and increases with temperature until the solubility becomes limiting.

The addition of sulfur to Na ^ S (reaction 4) and the addition of sulfur

Na ^ S · ^ (reaction 7) are the slowest and most sensitive reactions to temperature. Usually, molten sulfur is present in the form of a cyclic structure with 8 Sg atoms as a monoclinic sulfur. The effect of heat and the presence of hydroxide ions is to make the sulfur ring, thus transforming the monocyclic cyclic sulfur into a linear form. The resulting lilac shape is either an organized linear structure, orthorhombic sulfur, or a disorganized linear structure, amorphous sulfur. Both Na ₂ S and Na ₂ GSg will aggregate the sulfur molecules in one or the other ends of the sulfur chain to form, in the case of Na ₂ S, a polysulfide, Na ₂ S _x as Na ₂ S or, in the case of Na ₂ S In the case of Na ^ S ^, the corresponding tetratiocarbonate, read ₂ CS ^. Increasing the temperature increases the speed of both sulfur reactions, but particularly that of the sulfur reaction with NagCS ^, which is the slowest reaction and which limits the speed in most operating conditions. The reactive pathway that predominates at low temperatures and low concentrations is therefore the path defined by reactions 3,6 and 7.

At higher temperatures and concentrations, CS ₂ reactions begin to limit the speed due to the fact that the solubility of CS ₂ in the aqueous reactive phase is counterbalanced by high temperatures and high concentrations of Na ₂ GS ^. As the temperature increases, the rate of reaction 6 increases until it is limited by the solubility of GSg. At this point, reaction 6 starts to have the same speed as reaction 5. It follows that, for higher concentrations and shorter resistance times, the maximum temperature is limited. At high temperatures, sulfur reactions are faster, so the reactive vision that predominates at high temperatures is the path defined by reactions 3,4 and 5.

In general, a continuous process requires that the reactor volume, the reactor temperature, the

and the composition of the products are correlated so that sufficient residence time is provided for a complete conversion to the desired product. Compared to an overall process in which the total reaction time required can easily be provided in a continuous process is the residence time which determines the total reaction time.

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A continuous process is decidedly advantageous, because first and most importantly, a continuous process is generally the most convenient and effective way of carrying out chemical reactions, assuming that the given chemical reaction or reactions can be carried out continuously.

; The production speeds of continuous processes can be much higher than those of global processes. For example, while a global process would be able to produce about 1800 kg per day of an aqueous solution of sodium tetratiocarbonate with a concentration between 30 to 35 weight percent, the continuous process of the present invention can produce about 6800-9000 kg of solution of product per day, using the same size as the reactor.

Another advantage of the continuous process of the present invention is that it is capable of producing higher concentrations of sodium tetratiocarbonate than those obtained in the overall process, that is, concentrations up to about 55 weight percent. Even higher concentrations can be produced using the process of the present invention. However, for concentrations above 55 weight percent the reaction rate decays by decreasing the solubility of CSg in the aqueous reaction phase and because the carbonate contaminants introduced with the water start to precipitate. This last problem can be avoided using water without carbonates and bicarbonates.

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Now taking into account the design, a continuously stirred tank-type reactor 10 is equipped with a sulfur introduction pipe 12, a water supply pipe 14, a caustic soda pipe (NaOH) 16, a pipe of carbon 18 disulfide, a nitrogen (Ng) conduit 20 and a hydrogen sulphide conduit 22. Conduit 18 penetrates well into reactor 10.

The conduit 20 has a valve 24 and the conduit 22 has an i 26 valve. The reactor 10 is also equipped with a double agitator | 28 connected to a motor 30. The reactor 10 is shown containing | a solution 32. The reactor 10 has connected a visual level indicator 34. A heat exchanger 36 is connected to the reactor by a 3-way temperature control valve 37, a conduit 38, filters 40, a conduit 42, a pump 44 and a conduit 46. A conduit 48, also connected to the 3-way valve! 37, serves as a bypass for heat exchanger 36. Conduit 50 connects heat exchanger 36 to conduit 52, which serves as a recycling line and conduit 54, which is connected to the level control valve 55, and serves as connection to storage tanks, not shown. A scrubber 56 is equipped with a caustic tank 58 and a recycling line 60, which contains pump 62. Scrubber 56 is connected to reactor 10 via conduit 64. An emergency scrubber 66 is connected to reactor 10 via conduit 68 equipped with a rupture disc type valve for pressure relief 70.

In carrying out the process of the present invention, water is introduced into the reactor 10 through the water supply conduit 14. Although represented by entering the top of the reactor, water can be introduced into the reactor from both the top and the bottom. Water is generally introduced under environmental conditions.

However, at low temperatures it may be necessary to heat the water to prevent it from freezing.

hydroxide is introduced into the reactor or at the top, or the bottom,

as wished. In the drawing, the caustic is represented as entering the reactor 10 from the top, through the caustic pipe 16. Depending on the particular tetrathiocarbonate being produced, the corresponding hydroxide, such as sodium, potassium, ammonium, lithium, calcium or magnesium hydroxide, for example, it is introduced as an aqueous solution. Concentrations of 10 to 70 weight percent are typical examples. Preferably concentrations of 20 to 60 percent, or more preferably 40 to 50 percent by weight, are used. The hydroxide can be introduced at ambient conditions. It is however important that the temperature of the hydroxide is maintained above its freezing point.

Sulfur is introduced at the top of the reactor 10 through the sulfur feed line 12. The molten sulfur is sprayed into the reactor through the space occupied by the vapor above the surface of the liquid. Preferably the molten sulfur is introduced by a heated nozzle to prevent the sulfur from clogging the nozzle at the relatively lower temperature of the reactor. 0 molten sulfur is usually introduced at a temperature of 121-150 C ^2, preferably 135-140 ^ 0. Typically fused sulfur particle sizes of about 0.8 mm to 3.2 mm in diameter are used. Particles smaller than 3 mm in diameter are said to have produced the best results. Care must be taken that the molten sulfur particles do not touch any metal surface of the reactor, so that the molten sulfur is available to react, instead of solidifying on the metal surfaces of the reactor.

carbon disulfide is introduced into reactor 10 via the carbon disulfide duct 18. It is introduced below the surface of the liquid in the reactor so that it is available for the reaction in solution 32 and to prevent its contact with the sulfur particles in the steam above the solution

32. Preferably, the carbon disulfide is introduced near the stirrer 28 to ensure that the carbon disulfide is rapidly and evenly dispersed in the solution. The carbon disulphide can be introduced under ambient conditions.

hydrogen sulfide gaseous hydrogen sulfide is introduced into the reactor 10 via the hydrogen sulphide conduit 22. The volume introduced is regulated by valve 26. The hydrogen sulphide is preferably introduced into solution 32, below the stirrer 28, to ensure maximum dispersion in the phase liquid and to take advantage of the higher hydrostatic volume of the liquid inside the reactor, to give the complete reaction of hydrogen sulphide.

The process begins by filling the reactor with a product base followed by purging the vapor above the solution with nitrogen introduced into the reactor 10 through the nitrogen duct 20. The nitrogen flow is controlled by valve 24. The nitrogen leaves the reactor 10 through the duct 64 connecting the reactor to the scrubber 56. When the oxygen content of reactor 10 is less than about 0.3 weight percent, valve 24 is closed to stop the nitrogen flow. Simultaneously, water, hydroxide, sulfuric acid, molten sulfur and carbon disulfide are introduced into the reactor, resulting in the continuous production of tetratiocarbonate while maintaining the speeds for the introduction of the reagents.

The product is pumped out of the reactor 10 by means of a pump 44, through the ducts 46 and 42, to the filters 40 that work to remove any solids, such as sulfur, from the product stream. The filtered product goes to the 3-way temperature control valve 37 which maintains the temperature of the reactor 10 directing the product stream, total or

partially, for heat exchanger 36 or bypass line 48. Most of the cooler product is recycled back to reactor 10 via line 52. The rest of the product goes through line 54 to the level control valve 55 to be stored. The level 55 control valve keeps the liquid inside the reactor 10 at the desired working level.

The gases collected in the vapor phase of the reactor, above the liquid surface, are vented from the reactor by conduit 64 through the caustic scrubber 56. There is an emergency scrubber, as shown in the drawing. A rupture disc type valve 70 for pressure relief activates the emergency scrubber 66 when the pressure inside the reactor 10 has risen to an unacceptable level.

As stated above, in order to produce the desired products in the reactor, the temperature of the reagents and the composition of the process of the present invention, there is a correlation between volureactor, rates of introduction of the product. It is usual to express the introduction speeds in terms of dwell time, since this is inversely proportional to the introduction speeds. The correlation between the residence time and the reaction temperature, measured as the temperature of the liquid phase, for various product compositions is shown in Table 1.

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In general temperatures from about 43 to 82-C with times of perI

Immanencies of about 1 to 7 hours are effective in producing concentrations of tetratiocarbonates in the range of 30 to 55 weight percent. Especially preferred are temperatures of about 54 to 71 ^and C with residence times of about 2.5 to 4.5 hours. The best values are temperatures from 60 to 65-C with residence times of 3 to 4 hours.

The following example describes a process for the production of a 31.8 weight percent aqueous solution of sodium tetratlocarbonate. Its sole purpose is to be an illustration and should not be seen as implying any limitation on the horizon of the present invention, which is defined in the attached claims.

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EXAMPLE

As a base in a tank type reactor with continuous stirring, of 750 liters, an amount of 530 liters of a 31.8 weight percent aqueous solution of sodium tetrathiocarbonate. 0 reactor was purged with nitrogen and heated to 60 C. ² was introduced continuously into the reactor water at a rate 102.5 kg / hr., An aqueous solution of 50 percent sodium hydroxide at a rate of 68.54 kg / hr., sulfur fused at a rate of 12.43 kg / hr., carbon disulfide at a rate of 29.5 kg / hr., and gaseous hydrogen sulphide at a rate of 13.84 kg / hr. The molten sulfur was introduced at a temperature of 140 ° C. The reactor was maintained at a temperature of 63 ² G and a pressure of 1.05 kg / cm. A 31.8 weight percent aqueous solution of sodium tetrathiocarbonate was continuously produced at a flow rate of 226.8 kg / hour.

The present invention therefore provides a continuous process for producing salts of tetratiocarbonic acid as stable solutions of high concentration, for example, in the range of 30 to 55 weight percent.

This invention can be realized in other ways without departing from the spirit or essential characteristics for that reason. For example, as mentioned above, other salts of tetratiocarbonic acid can be prepared using the process of the present invention. Consequently, the forms present are to be considered merely illustrative and not restrictive, the scope of the invention being indicated by the appended claims. All embodiments that fall within this horizon or are equivalent to the claims are therefore included here.

Claims (98)

completed. 1-. _ Process for the preparation of an aqueous solution of a salt of tetratiocarbonic acid, characterized by the fact that it comprises the operations that consist of reacting an aqueous solution of a hydroxide with sulfuric acid to produce an aqueous solution of the corresponding sulfide; reacting the resulting sulfide, in aqueous solution, with molten elemental sulfur, to obtain an aqueous solution of the corresponding disulfide; and reacting the resulting disulfide in an aqueous solution with carbon disulfide to obtain an aqueous solution of the corresponding salt of tetratiocarbonic acid. I í 2 ^â . Process according to claim 1, characterized in that said salt of tetrathiocarbonic acid is a compound chosen from the group formed by tetrathiocarbonate tetrathiocarbonate tetrathiocarbonate tetrathiocarbonate tetrathiocarbonate sodium, potassium, ammonium, lithium, calcium and magnesium . 3 ^â . Process according to claim 1, characterized in that said salt of tetratiocarbonic acid is sodium tetratiocarbonate. 4 ^â . Process according to claim 1, characterized in that said aqueous solution of the tetra thiocarbonic acid salt has a concentration greater than 30 weight percent. 5 ^â . Process according to claim 1, characterized in that said hydroxide, sulfuric acid, sulfur and carbon disulfide are reacted in approximately stoichiometric proportions. 6S. Process according to claim 1, characterized in that said hydroxide is reacted with hydrogen sulphide at a temperature in the range between about 43.3 ² C (110 ² F) and about 76.7 ² C (170 ⁹ P); said sulfide is reacted with sulfur at a temperature in the range of about 60O 2C (1402 p) to about 76.7 ² C (1702 p) and the said disulfide is reacted with carbon disulfide at a temperature in the range about 57.220 ⁽² 135 P) 71.1 ² C (1602 F). 72. The method of claim 1, wherein said hydroxide is present in a concentration of about 15% ^to about 35% by weight. 82. The method of claim 1, wherein said hydroxide solution is maintained at a temperature of at least about 43.3 ² C (110 ² P). 9 ^â . Process according to claim 1, characterized in that said hydroxide is reacted with hydrogen sulphide at a pressure higher than atmospheric pressure. 102. Process according to Claim 1, characterized in that said hydrogen sulphide is reacted with said hydroxide at a temperature in the range of about 43.3 ² C to about 76.7 ² C (1102 p - 1702 F). 112. Process according to Claim 1, characterized in that said sulfide is reacted with said sulfur at a temperature between about 60 ² G and about 76.7 ² 0 (140 ² P - 170 ² P). 12 ^â . - Process according to claim 1, caracterizajdo in that carjbono reacting said disulfide with said disulfide at a temperature realized | in the range of between about 0 and about 57.2 ² 71.1 ² C ( 135 ² ; P - 1602 p). 13-. Process according to claim 1, characterized in that said carbon disulfide and sodium disulfide are reacted at a pressure above atmospheric pressure. | 14 ^â . Process according to claim 3, characterized i due to the fact that said aqueous solution of sodium tetrathiocarbonate has a density ranging from about 1.20 to about 1.30, to 21,120 (702 p). 15 ^ã . - Process for the preparation of an aqueous solution of sodium tetra · thiocarbonate, characterized by the fact that it comprises the operations that consist of feeding into a reaction zone, an aqueous solution of sodium hydroxide with a concentration between about 15 and about 35 weight percent at a temperature of at least 43.3 ² C (110 ² p) approximately; if hydrogen sulphide gas is introduced near the bottom of the aforementioned solution at a pressure between about 0.175 kg / cm relative (2.5 psig) and about 0.7 kg / cm relative (10 psig), to govern with the said sodium hydroxide and give an aqueous sodium sulfide solution; melt elemental sulfur over the surface of the aqueous solution resulting from sodium sulphide, with stirring, to mix and react with the aforementioned sulphide. I sodium, with a temperature in the range of about 60 ² C to about 76.7 ² C (140 ² P - 170 ² p), until all the sulfur has reacted and an aqueous solution of sodium disulfide is produced ; i 1 6 Carbon disulfide is introduced below the surface (from the resulting aqueous solution of sodium disulfide with agglutination, at a temperature from about 57.2 ² G (135 ² P) to 5 about 71> 1 ² C (160 ² P) and a pressure comprised in the inter ¹ 2, range between about 0.35 kg / cm relative (5 psig) to about 1.4 kg / cm relative (20 psig ) to react with said sodium disulfide and produce an aqueous solution of sodium tetrathiocarbonate having a concentration greater than about 30 weight percent; using the mentioned sodium hydroxides, hydrogen sulphide, sulfur and carbon disulfide in approximately stoichiometric proportions. Process according to claim 15, characterized in that the said aqueous sodium hydroxide solution is prepared by mixing a sodium hydroxide solution with water. 17th. Process according to claim 15, characterized in that said sodium hydroxide is present in an excess in the range of about 5 to about 15 percent. 18 &. Process according to claim 15, characterized in that the said temperature of the sodium hydroxide solution is maintained by adding heat to said reaction zone. 19 ^â . Process according to claim 15, characterized in that continuous stirring of said reaction zone is carried out. 20th. Process according to claim 15, characterized in that said hydrogen sulphide is introduced in a maximum excess of about 5 percent. 21 ^ã . Process according to claim 15, characterized in that the said pressure is maintained during the introduction of the hydrogen sulfide by discharge from the reaction zone in order to relieve the pressure due to the inert gases existing with the said hydrogen sulfide. 22 ^. Process according to claim 21, characterized in that said exhaust is carried out continuously during said introduction of hydrogen sulphide. 23 ~. Process according to claim 21, characterized in that said discharge takes place at the end of said introduction of hydrogen sulphide. 24 ^â . Process according to claim 15, characterized in that the granulometry of said sulfur that is present is less than 3.175 mm (1/8 inch) in diameter. fact** 25 ^ã . Process according to claim 15, characterized in that the said molten elemental sulfur is sprayed in order to avoid its contact with the metal surfaces existing in said reaction zone. I I 26? -. Process according to claim 15, characterized in that the temperature is maintained during the reaction of said sodium disulfide with carbon disulfide by cooling. 27 ^â . Process according to claim 15, characterized in that the reaction of said sodium disulfide with carbon disulfide is carried out, without discharge. 28 ^. Process according to claim 15, characterized in that the pressure rises to about 0.7 to 1.4 kg / cm 2 relative (10 to 20 psig) during the reaction of the said sodium disulfide with the sodium disulfide carbon, to produce> said sodium tetratiocarbonate. 29-. Process according to claim 15, characterized in that the aforementioned aqueous solution of sodium tetratiocarbonate has a concentration in the range between about 31% and about 35% by weight. £ 30. Process according to claim 15, characterized in that said aqueous solution of sodium tetratiocarbon has a concentration equal to about 31.8 by weight. Process according to claim 15, characterized in that said aqueous solution of sodium tetratiocarbonate is a clear solution. ! 32 ^â . Process according to claim 15, characterized in that the aforementioned aqueous solution of sodium tetrathiocarbonate does not contain sulfur or free carbon disulfide. 33-. Process according to claim 15, characterized in that the aforementioned aqueous solution of sodium tetrathiocarbonate has a density of about 1.26 to 21 ° C (70 ° P). 34-. Process according to claim 15, characterized in that said reaction zone is essentially oxygen-free. 35 ^â . - Process for the preparation of an aqueous solution of a salt of tetratiocarbonic acid, characterized by the fact that it comprises the operations that consist of feeding an aqueous solution of a hydroxide to a reaction zone with a concentration between about 15 and about 35% percent by weight at a temperature of at least 43.3 ² C (110 ² F) approximately; gaseous hydrogen sulphide is introduced near the bottom of the solution at a pressure in the interval between n about 0.175 kg / ccnr relative (2.5 psig) and about 0.7 kg / cm2 relative (10 psig), to react with said hydroxide and produce an aqueous solution of the corresponding sulfide; melting elemental sulfur over the surface of the aqueous solution resulting from the corresponding sulphide, with stirring, to mix and react with said sulphide at a temperature between about 60 ° C and about 76.72 ° C (1402 ° C) p - 1702 p), until all the sulfur has reacted, to produce an aqueous solution of the corresponding disulfide; and introducing carbon disulfide under the surface of the aqueous solution resulting from the disulfide with stirring, at a temperature from about 57.2 ² C (135 ² F) to about 71.1 ^S C (1602 F) and a pressure in the range between about 0.35 kg / cm2 relative (5 psig) to about 1.4 kg / cm relative (20 psig), to react with said disulfide and produce an aqueous solution of the corresponding ijsal tetratiocarbenic acid having a concentration greater than about 30 weight percent; using said hydroxide, sulfuric acid, sulfur and carbon disulfide in approximately estetuiometric proportions. 36. The method of claim 35, wherein said tetrathiocarbonic acid salt is chosen from the group consisting of tetrathiocarbonate tetrathiocarbonate tetrathiocarbonate, tetrathiocarbonate, sodium, potassium, ammonium, lithium, calcium and magnesium. 37-. The process according to claim 35, characterized. that the said aqueous sodium hydroxide solution is prepared by mixing a solution of said hydroxide with water. I i 38th. Process according to claim 35, characterized in that said hydroxide is present in an excess comprised between about 5 and about 15 percent. ^! , 39-. Process according to claim 35, characterized in that continuous stirring is carried out in said reaction zone. 40 ^. Process according to claim 35, characterized in that continuous stirring is carried out in said reaction zone. 41 ^& . Process according to claim 35, characterized in that hydrogen sulphide is introduced in a maximum excess equal to about 5 percent of the stoichiometric proportions. 42§. Process according to claim 35, characterized in that the aforementioned pressure is maintained during the introduction of hydrogen sulphide by discharge of gases from the reaction zone, in order to relieve the pressure due to the inert gases existing in mixture with the mentioned hydrogen sulphide . 43-. Process according to claim 42, characterized in that the aforementioned gas discharge is carried out continuously during the mentioned introduction of hydrogen sulphide. : 44-. Process according to claim 43, characterized in that said gas discharge takes place at the end of said introduction of hydrogen sulphide. 45-. Process according to claim 35, characterized in that said sulfur is present with a particle size less than 3.175 mm (1/8 inch) in diameter. 46 &. Process according to claim 35, characterized in that said molten elemental sulfur is sprayed in such a way as to avoid its contact with the metallic surfaces existing in said reaction zone. i 47-. Process according to claim 35, characterized in that the temperature during the reaction between said disulfide and carbon disulfide is maintained by cooling. 48th. Process according to claim 35, characterized in that the reaction of said disulfide with carbon disulfide is carried out, with no gas space for the atmosphere. 49-. Process according to claim 35, characterized in that the pressure rises to about 0.7 to 1.4 kg / cm relative (10 to 20 psig), during the reaction of said disulfide with the carbon disulfide, to produce said tetratiocarbonic acid salt. 50§. Process according to claim 35, characterized in that the aforementioned aqueous solution of the tetratiocarbonic acid salt has a concentration ranging from about 31 to about 35% by weight. 51 ^â . Process according to claim 35, characterized in that said aqueous solution of the tetratiocarbonic acid salt has a concentration equal to about 31.8 γ by weight. 52 ^â . Process according to claim 35, characterized in that said aqueous solution of tetratiocarbonic acid salt is a clear solution. 53-. Process according to claim 35, characterized in that the said aqueous solution of tetratiocarbonic acid salt does not contain sulfur in a free carbon disulfide. 54 ^â . Process according to claim 35, characterized in that the aforementioned aqueous solution of sodium tetratiocarbonate has a density equal to about 1.26 to 21.1 ° 0 (70 ° P). 55-. Process according to claim 35, characterized in that said functional zone is essentially free of oxygen. 5S§. - Continuous process for the preparation of an aqueous solution of a salt of tetrathiocarbonic acid, characterized by the fact that it comprises the operation of continuously reacting a tetrathiocarbonate tetrathiocarbonate tetrathiocarbonate tetrathiocarbonate tetrathiocarbonate aqueous mixture of a hydroxide, sulfur, carbon disulfide and hydrogen sulphide, at a temperature in the range of about 43.3-C (110 ⁹ P) to about 82.2 ² C (180 ² P) to produce an aqueous solution of a salt of tetratiocarbonic acid. i 57®. Process according to claim 56, characterized in that said salt of tetratiocarbonic acid is a compound chosen from the group formed by sodium, potassium, ammonium, lithium, calcium and magnesium. 58®. Process according to claim 56, characterized in that said salt of tetratiocarbonic acid is sodium tetratiocarbonate. 59®. Process according to claim 56, characterized in that said aqueous solution of a salt of tetratiocarbonic acid has a concentration greater than 15 weight percent. 60®. Process according to claim 56, characterized in that the aforementioned aqueous solution of a salt of tetratiocarbonic acid has a concentration in the range between about 30 by weight and 55 by weight. 61§. Process according to claim 56, characterized in that said hydroxide, sulfur, disulfide If carbon and hydrogen sulphide are subjected to reaction in i i approximately stoichiometric proportions. 622-. Process according to claim 56, characterized in that said aqueous mixture contains an excess ranging from about 5 percent to about 10 percent by weight of said hydroxide and hydrogen sulfide. i63-. Process according to claim 56, characterized in that said aqueous mixture contains an excess in the range between about 10 percent and about 5 percent by weight of said hydroxide and hydrogen sulphide. 64 ^ã . Process according to claim 56, characterized in that the aqueous mixture of hydroxide, sulfur, carbon disulfide and hydrogen sulphide is reacted at a pressure above atmospheric pressure. ^£ 65. Process according to claim 64, characterized in that the said pressure is between 0.35 and 2.1 kg / cm relative (5 psig and about 30 psig) at the end of the interval. 66th. - Process according to claim 56, characterized in that the said temperature is in the range between about 54.4 and about ² C ² 71.1 C (about 1302 to about 1602 P P). 67 ^â . - Process according to claim 56, 'wherein said temperature is between about βΟ ^C-9 and about 65.6 C (about 140 - P and about 1502 p). I I 683. The process of claim 56, wherein the residence time for carrying out the reaction of said hydroxide, sulfur, carbon disulfide and hydrogen sulphide is between about 1 hour and about 7 hours. j69 ^â . Process according to claim 56, characterized in that the residence time for carrying out the reaction of said hydroxide, sulfur, carbon disulfide and hydrogen sulphide is between about 2.5 hours and about 4, 5 hours. 70 &. Process according to claim 56, characterized in that the residence time for carrying out the reaction of said hydroxide, sulfur, carbon disulfide and hydrogen sulphide is between about 3 hours and about 4 hours. 71-. - Continuous process for the production of an aqueous solution of a salt of tetratiocarbonic acid, characterized by the fact that it comprises the operations of feeding, continuously and simultaneously, to a stirred reaction zone, separate streams of water, from an aqueous solution of a hydroxide, fused sulfur, carbon disulfide and hydrogen sulfide gas; to maintain the said reaction zone at a temperature between about 43.3-0 (110 ^s P) and about 82.2 ² G (180 ² 3?), with the residence time between about 1 hour and about 7 hours; and continuously recovering, from said reaction zone, an aqueous solution of a salt of tetratiocarbonic acid having a concentration comprised between about 15 weight percent and about 55 weight percent. 72 ^. Process according to claim 71, characterized in that said salt of tetratiocarbonic acid is a compound chosen from the group formed by tetratiocarbonate tetratioc arb onat tetratiocarbonate tetratiocarbonate tetratiocarbonate tetratiocarbonate sodium, potassium, ammonium, lithium, calcium and magnesium. 73 ^â . Process according to claim 71, characterized in that said salt of tetratiocarbonic acid is tetratiocarbonic sodium. 74 ^â . Process according to claim 71, characterized in that said hydroxide, sulfur, hydrogen sulphide and carbon disulfide are fed in approximately stoichiometric proportions. 75â. Process according to claim 74, characterized in that said hydroxide and hydrogen sulphide are fed in an excess comprised between about 5 percent and about 10 percent by weight. 76ã. Process according to claim 74, characterized in that said hydroxide is fed in an excess equal to about 10 weight percent and said hydrogen sulfide is fed in an excess equal to about 5 weight percent. 77 ^â . Process according to claim 71, characterized in that said water is fed close to the upper part of said reaction zone. 78§. Process according to claim 71, characterized in that said hydroxide is fed close to the upper part of said reaction zone. 79 ^â . Process according to claim 71, characterized in that said molten sulfur is fed close to the upper part of said reaction zone. 80 ^. Process according to Claim 71, characterized in that said carbon disulfide is fed below the surface of the liquid in the reaction zone. 81 ^. Process according to claim 71, characterized in that said hydrogen sulphide is fed over the bottom of said reaction zone. 82®. Process according to claim 71, characterized in that said water is fed under environmental conditions. 832. The process of claim 71 wherein said aqueous solution of a hydroxide is fed at a temperature above its freezing point. 84 ~. Process according to claim 71, characterized in that said aqueous solution of a hydroxide is an aqueous solution of a hydroxide chosen from the group formed by hydroxide, potassium hydroxide, ammonium, lithium hydroxide, calcium hydroxide and magnesium hydroxide. 85 ^â . Process according to claim 71, characterized in that the said aqueous solution of a hydroxide is an aqueous solution of sodium hydroxide. 862. A process according to claim 71, characterized in that said aqueous solution of a hydroxide has a concentration ranging from about 10 percent to about 70 weight percent. 87 ^â . Process according to claim 71, characterized in that said aqueous solution of a hydroxide has a concentration ranging from about 20 percent to about 60 percent by weight. 8. A process according to claim 71, characterized in that said aqueous solution of a hydroxide has a concentration in the range of about 40 percent to about 50 percent by weight. ^ 89 ^â . Process according to claim 71, characterized in that said molten sulfur is fed at a temperature in the range between approximately 121.1 0 (250 ² P) and approximately 148.9 ² 0 (300 ² P) . 90 &. Process according to claim 71, characterized in that said molten sulfur is fed at a temperature in the range between about 135 ² C (275 ² P) and about 140, (285 ² P). 91st. Process according to claim 71, characterized in that said molten sulfur is sprayed into the reaction zone. 92 ^. Process according to claim 91, characterized in that the particle size of the powdered molten sulfur droplets is in the range between about 0.79 mm (1/32 inch) and about 9.5 mm (3/8 inch). 93a. Process according to claim 91, characterized in that the particle size of the sprayed molten sulfur droplets is less than 3.2 mm (1/8 inch). 94a. Process according to claim 91, characterized in that said molten sulfur is sprayed into said reaction zone in order to avoid contact with the metal surfaces existing in said reaction zone. 95 ^â . Process according to claim 71, characterized in that said reaction zone is maintained at a temperature between about 54.42c (ISO ² 3?) And about 71, l ² 0 (ISO ² F) . 962. A process according to claim 71, characterized in that said reaction zone is maintained at a temperature between about 60 ² C (140 ² F) and about 65.5 ² 0 (150 ² F). 97 ^â . Process according to claim 71, characterized in that the residence time is between 2.5 hours and approximately 4.5 hours. Process according to claim 71, characterized in that the aforementioned dwell time is between about 3 hours and about 4 hours. 99. The method of claim 71 wherein the said aqueous solution of a salt of tetrathiocarbonic acid has a concentration in the range of about 30 weight percent to about 55 weight percent. 1002. The process of claim 71 wherein said aqueous solution of a salt of tetratiocarbonic acid has a concentration in the range of about 40 weight percent to about 50 weight percent. 101 ^& . - Continuous process for the production of an aqueous solution of a salt of tetratiocarbonic acid, characterized by the fact that it comprises the operations that consist of feeding continuously, to a stirred reaction zone, separate streams of water, an aqueous solution of a hydroxide, molten sulfur, sulfur disulfide carbon and hydrogen sulfide gas; the aforementioned hydroxide, sulfur, carbon disulfide and hydrogen sulphide are continuously reacted at a temperature between about 43.3 ² G (110 ² P) and about 82.2 ² C (180 ² P) , with a residence time between about 1 hour and about 7 hours; and continuously recovering, from said reaction zone, an aqueous solution of a salt of tetratiocarbonic acid having a concentration in the range of approximately 15% to 55% by weight. 102 ^. Process according to claim 101, characterized in that said salt of tetratiocarbonic acid is a compound chosen from the group formed by sodium, potassium, ammonium, lithium tetrathiocarbonate, calcium tetrathiocarbonate and magnesium tetrathiocarbonate tetrathiocarbonate . 103 '- The process according to claim 101, characterized in that the said tetratioearbónico acid salt is sodium tetrathiocarbonate. 104 ^â . Process according to claim 101, characterized in that said hydroxide, sulfur, hydrogen sulphide and carbon disulfide are fed in approximately stoichiometric proportions. 105-. Process according to claim 104, characterized in that said hydrogen hydroxide and sulfide are fed with an excess in the range between about 5 percent and about 10 percent by weight. lOSã. Process according to claim 104, characterized in that said hydroxide is fed with an excess equal to about 10 weight percent and said hydrogen sulfide is fed with an excess equal to about 5 percent, in weight. 107 ^â . Process according to claim 101, characterized in that said water is fed close to the upper part of said reaction zone. 108a. Process according to claim 101, characterized in that said hydroxide is fed close to the upper part of said reaction zone. 109§. Process according to claim 101, characterized in that said molten sulfur is fed close to the upper part of said reaction zone. 110-. Process according to claim 101, characterized in that said carbon disulfide is fed below the surface of the liquid in said reaction zone. llllã. Process according to claim 101, characterized in that said hydrogen sulfide is fed near the bottom of said reaction zone. 112 &. Process according to claim 101, in that said water is fed with environmental conditions. Characteristic as con 113 ^â . Process according to claim 101, characterized in that said aqueous solution of a hydroxide is fed at a temperature higher than that of its freezing point 114-. Process according to claim 101, characterized in that said aqueous hydroxide solution is an aqueous solution of a hydroxide chosen from the group consisting of sodium hydroxide, potassium hydroxide, ammonium, lithium hydroxide, calcium hydroxide and hydroxide. magnesium. 115. The process according to claim 101, characterized in that the said aqueous solution of a hydroxide is an aqueous solution of sodium hydroxide. 116-. Process according to claim 101, characterized in that said aqueous hydroxide solution has a concentration ranging from about 10 percent to about 70 weight percent. ί117- method according to claim 101, caracteri ¹ Zado in that said aqueous solution of a hydroxide has a concentration in the range between about 20 percent and about 60 percent by weight. 11. A process according to claim 101, characterized in that the aforementioned aqueous solution of a hydroxide has a concentration in the range from about 40 percent to about 50 percent by weight. II93. Process according to claim 101, characterized in that said molten sulfur is fed at a temperature in the range between approximately 121,120 (2502 F) and approximately 149,820 (3002 p) _} . 1203. - A method according to claim 101, wherein 0 said molten sulfur is fed at a temperature in the range of about 135 ° C (275 P ²⁾ and about 140.520 (285 F ^2). 12. The process of claim 101 wherein said molten sulfur is sprayed into the reaction zone. 122a. Process according to claim 101, characterized in that the particle size of the powdered molten sulfur droplets is between about 0.79 mm (1/32 inch) and about 9, 5 mm (3/8 inch). {123-. Process according to claim 101, characterized in that the particle size of the powdered molten sulfur droplets is less than 3.175 mm. (1/8 inch). 124 ^sec . Process according to claim 101, characterized in that said molten sulfur is sprayed into said reaction zone in order to avoid contact with the metal surfaces existing in said reaction zone. 125 ^s . - Method according to claim 101, wherein said maintaining the reaction zone at a temperature in the range from about 54.4 L ² (P 1302) and about 71.1 ² C (1602 p). 126 ^. Process according to claim 101, characterized in that said reaction zone is maintained at a temperature between about 6020 (1402 P) and about 65.620 (1502 P). 127. The method of claim 101, wherein the residence time is between approximately 2.5 hours and 4.5 hours. ! l28§. Process according to claim 101, characterized in that the said residence time is between about 3 hours and about 4 hours. 129 ^â . Process according to Claim 101, characterized in that the said aqueous solution of a tetratiocarbonic acid salt has a concentration of no. range between about 30 weight percent and about 55 weight percent. 130 ^. Process according to claim 101, characterized in that said aqueous solution of the tetratiocarbonic acid salt has a concentration in the range between about 40 weight percent and about 50 weight percent.