US471780A - sniffin - Google Patents

Description

(No Model.)

E.1WALL BR & C.`A.VSNIFFIN. METHOD 0F MAKING WHITE LEAD.

NO- 471,730 Patented Mar. 29, 1892,

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UNITEI) STATES PATENT OFFICE..

ELXVYN WALLER AND CHARLES `SNIFFIN, OF NEW YORK, N. Y.

METHOD OF MAKING WHITE LEAD.

SPECIFICATION forming part of Letters Patent No. 471,780, dated March 29, 1892.

Application filed September 5, 1891.

To all whom t may concern:

Be it known that we, ELWYN WALLER and CHARLES A. SNIFFIN, both citizens of the United States, and residents of the city, county, and State of New York, have invented cer- 'tain Improvements in 'Methods of Making W'hite Lead, of which the following is a speciiication.

This invention relates to the production of white lead for use as a pigment directly from the carbonate ore, an impure cerussite, such as is found in the vicinity of Leadville, Colorado, and various other places in the western part of the United States.

We have discovered that when the native carbonate ore is heated to ebullition with a solution containing either acetic acid or lead acetate the ore will yield more or less of the lead it contains to the solution, and if the proportion of acetic acid or lead acetate be sufiicient and the period of heating be adequately prolonged the whole of the lead contained in the carbonate of the ore treated will be taken up and dissolved in the solution. When neutral lead acetate is used basic acetates of lead go into the solution, and when acetic acid is used neutral or basic acetate of lead are formed, according to the proportion of real acetic acid used and the amount of same, which may be allowed to boil away. Vhen neutral lead acetate is used,or when we use less acetic acid than will sufce to form a neutralv tained. This lead hydrocarbonate is theA White lead of commerce used extensively as a pigment. After 'the treatment with carbon dioxide neutral leadacetate remains in the solution, and this solution may be employed in the treatment of a fresh portion of the ore, thus effecting an economyin the acetic acid employed, which is used over and over again, and the carbon dioxide evolved in the treatment of the ore primarily is or may be collected and employed in the after precipitation of the lead h'ydrocarbonate,

Serial No. 404,867. (No specimens.)

whereby an important economy in the production of this gas is effected.

In respect of the ratio of acetic acid or lead acetate to be used to the amount of lead present in the carbonate of the ore treated, it .should be borne in mind that where the proportion of acetic acid is too small there is a liability of producing highly basic lead acetates which are less soluble in water than the less highly basic acetates, and therefore render the process less advantageous on'accountof the necessity of handling larger quantities of the solution. We will hereinafter give the proportions We have employed with good results. We do not, however, limit ourselves to these proportions.

Having thus stated in a general Way the principles upon which our manufacture is based, we will now proceed to set forth more definitely how it may be carried out in practice.

The carbonate ore should be first ground or pulverized so finely that it will pass through a sieve having forty, iifty, or sixty meshes to the linear inch. The liner it is ground the more rapid and satisfactory will be the operation. An analysis should then be made of a fair average portion of the ore to determine the percentage of lead present, as this percentage varies greatly in ores from dierent localities. A convenient amount or charge of the ground ore isthen placed in a vessel arranged over a furnace or adapted to be otherwise heated. The volume of the charge will be governed by the percentage of lead contained in the ore. Water to the amount of about fifteen or twenty times the weight of lead in the charge is now added, and to this added for the first charge reall acetic acid in the proportion of about one-fifth the Weight of the lead in the charge, or, more exactly, six hundred and twenty-one parts of lead to one hundred and twenty parts of acetic acid.- The amount of water contained in the acetic acid added, if ordinary commercial acid be used, should be reckoned in the calculation as a part of the water in the charge. By real acetic acid is here meant the anhydrous or actual acetic acid (HCQHSOQ) as distinguished from commercial acetic acid, which is a mixture of acetic acid and water.- If neutral lead acetate IOO be used, the amount, by weight, of the acetate should be nearly equal to the lead present, or,

parts of crystallized neutral lead acetate tofour hundred and fourteen parts of metallic lead present in the charge. lThese proportions are not liable to produce a basic acetate higher than the tri-basic when the process is carried out as described; but if any departure be made from these proportions we prefer to increase the amount of acetic acid or the solution of neutral acetate.

The Vessel containing the charge may beef enameled iron or other suitable material, and the charge should not fill it more than about one-third full. It should have a close-fitting cover and be provided with aA rotating mechanical stirrer and an. outlet for the carbon dioxide which leads through a condenser to a gas-holder. After the vesselis charged and lthe stirrer set in operation, heat is lapplied and the temperature raised until the contents boil gently or simmer. This heat should be maintained for from four to six hours continuously.

The siirrer is not absolutely essential; but it is useful, because, unless the heat be very carefully regulated, the contents of the vessel are apt to boil over. As'low a heat as possible consistent with the necessity of keeping the mass gently simmering is best. At the endof from four to six hours about one-half of thewater should haveboiled away. The actual length of time required for maintaining the heat in any given case will depend somewhat upon the purity of the ore, the management of the heat, and similar conditions. When the period of boiling shall have terminated, the charge is allowed time to settle.

The Water driven olf as vapor fromV the charge and the carbon dioxide which is driven off with it are passed through a coil or condenser, which should be kept as cold as possible in order that the water of condensation may absorb as much of the carbon dioxide as possible, and this water, as well as the free carbon dioxide, is led from the condenser into a closed vessel or, better, a gas-holder,where it is stored. Pipes from this holder lead the carbonated water and the free carbon dioxide into a precipitatingtank or vessel, the liquid iowing into the tank in any manner desired and the gas entering below the level of the said liquid. The charge in the boiling-vessel, as soon as the heat is withdrawn, settles rapidly, leaving only a few finely-divided particles of the residuum in suspension. To obtain perfectly-pure white lead, these particles should be removed by passing the supernatant solution in the vessel (now containing basic lead acetates) through a iilter. While still hot, it is led to the tank containing the carbonatedwater and carbon dioxide passed through the mixture, when a reaction takes place and the lead is precipitated in the form of amorphous lead hydrocarbonate or white lead. l

We have discovered that when a solution of basic lead acetate is quite dilute, or when precipitation is induced at once by mingling the drocarbonate is obtained, and the uncombined v carbon dioxide arising from the precipitating- -vessel may be conveyed to a gas-holder for further use. l

The amount of carbon dioxide set free from the ore treated should be more than sufficient for the precipitation of the lead hydrocarbonate in the tank, since lead is present in the ore as a neutral carbonate, (PbCO3,) containing forty-four parts of carbon dioxide to two hundred and seven parts of metallic lead, whereas the white lead of commerce contains from twenty-seven and a half to thirty-six and two-thirds parts of carbon dioxide to two hundred and seven parts of lead. The more common proportion is twenty-nine and one'- third parts carbon dioxide to two hundred and seven parts metallic lead. However, as some carbon dioxide may be lost'by leakage it may be necessary. to manufacture a por'- tion of that required by some one of the wellknown methods. lf a large excess of carbon dioxide be employed the precipitate tends to become crystalline, and consequently deficient in covering power or body when used as a pigment. Hence it is advisable to stop the introduction of the carbon dioxide when the solution in the tank (which will be milky) shows a tendency to clear up rapidly. After precipitation time is allowed for the solution to become clear, when it is drawn od from the tank for use with another charge. The precipitate is removed, washed, and dried in the usual manner.

Our object in using carbonated Water` or Water charged with carbon dioxide in the precipitating-tank and passing carbon dioxide in a gaseous form through the solution in said tank is to avoid crystallization and render the precipitate amorphous.

The residual ore froni the treatment may retain some lead in the form of basic acetate probably in a more basic forni than the tribasic, and the amountwill be larger if the solution be allowed to cool in contact with it. If desired, practically all of this basic acetate may be recovered by boiling the residue in water. l

In the accompanying drawing I we have shown somewhat diagrammatically an apparatus adapted for carrying out our method.

l represents the vessel or retort in which the charge is boiled or simmered forfrom four to six hours. This vessel is represented as mounted on trunnions 2 over a furnace 3 or any form of heating apparatus, so that it may be tilted for decanting int-o a lter 4,

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from which the solution of basic acetate iiows by a pipe 4E to the precipitating -.tank 5. Within the vessel l is a mechanical stirrer, (indicated in dotted lines,) the shaft 6 of which has on it a bevel-wheel 7, which gears with a similar wheel 8 on a power-shaft 9.'

The removable cover l of the vessel 1 is provided with a gas and vapor outlet 1" which is coupled by a suitable union with a jointed pipe 10, which leads the carbon dioxide and watery vapor from the vessel 1 to the condenser 11, from which the free gas and the carbonated water pass to a holder 12, provided with a counterweighted bell-cover 12". The water remains in the holder and seals the bell, while the free gas rises in the bell. The carbonated water from the holder 12 iiows into the precipitating-tank by way of a cock- Y controlled pipe 13, and the gas from the bell l2 enters thertank below the liquid level therein by way of a pipe 14, that portion of said pipe within the tank being perforated. After the precipitationof the white lead in the tank, the remaining solution of neutral lead acetate is drawn off bya cock 15 for use with the next charge treated.

The rotary stirrer may be removed from vessel 1 by lifting it with the cover of the vessel tofacilitate cleaning and the removal of the residual ore. The free carbon dioxide escapes from the tank 5 at an outlet 16.

Any other apparatus of a similar character to that illustrated may be employed.

XVe may say here that we use acetic acid only with the first charge treated by preference, and for the succeeding charge we employ the solution of neutral lead acetate from t-he precipitating-tank for ad mixture with the water and pulverized ore. Of course we may employ acetic acid with each charge, or a solution of the neutral lead acetate with each charge; but for economical reasons we prefer to'operate as above stated. ln each case the acetic acid is the active agent, whether combined in the form of the neutral acetate or not, and so far as our process or methodis concerned the diluted acetic acid used with the rst charge is the equivalent of the solution of neutral lead acetate used with the subsequent charges.

Having thus described our invention, we claim- 1. The herein-described method of producing asolution of a basic lead acetate from lead carbonate, which consists in heating the carbonate with water containing neutral lead acetate, substantially as set forth.

2. The herein-described method of producing lead hydrocarbonate or white lead directly from ores containing lead carbonate, which consists in heating said ores with water containing neutral lead acetate, whereby a solution of a basic lead acetate is obtained and then precipitating the lead hydrocarbonate from this solution with carbon dioxide, substantially as set forth.

3. The herein-described method of producing lead hydrocarbonate or white lead directly from ores containing lead carbonate, which consists in first heating said ores with water containing neutral lead acetate, whereby asolution of a basic lead acetateis obtained, then mixing this solution with water charged with carbon dioxide and passing through the mixture carbon'dioxide in its gaseous form, whereby lead hydrocarbonate of a highly amorphous character is precipitated, substantially as set forth.

4. The herein-described method of producing lead hydrocarbonate or white lead direct from the native lead carbonates, which consists in viirst mixing together the carbonate ore, water, and neutral lead acetate, then heating the mixture to ebullition and maintaining this heat until the lead in the ore has been converted into a basic acetate and the latter dissolved, then mixing the solution of basic acetate with Water charged with carbon dioxide and passing through said mixture carbon dioxide in a gaseous form until the lead shall have been precipitated thereform in the form of lead hydrocarbonate, substantially as set forth.

5. The herein-described method of yproducing lead hydrocarbonate from a solution of a basiclead acetate, which consists in mixingthe said solution with water charged with carbon dioxide and passing through said mixture carbon dioxide in its gaseous form, whereby the lead is precipitated in the form of a hydrocarbonate, substantially as set forth.

6. The herein-described method of producing amorphous lead hydrocarbonate from a solution of a basic lead acetate, which consists in mixing said solution while hot with water charged with carbon dioxide and passing through said mixture carbon dioxide in its gaseous form until the mixture begins to clear, substantially as and for the purposes set forth. I

7. The herein-described method of producing lead acetates from ores containing lead carbonate, which consists in mixing together the ore, water, and acetic acid in substantially the proportions specified, and then heating this mixture to ebullition and maintain-A ing the heat until the lead of the carbonate in the charge is converted and taken up in solution.

S. The herein-described method of making white lead from ores containing lead carbonate, whichconsists in heating the ore'to ebullition with a solution of neutral lead acetate from a previous charge until the lead in the ore is converted into a basic acetate, which is taken up in solution and the carbon dioxide from the ore is driven oft and stored, and then mixing the solution of basic acetate with carbonated water and passing through it the free carbon dioxide driven off from the ore, as set forth.

. In witness whereof we have hereunto signed our names in the presence of two subscribing witnesses.

ELWYN WALLER. CHAS. A. SNIFFIN.

Witnesses:

HENRY CONNETT, HERBERT BLossoM.

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