US1175565A - Method of making lead arsenate. - Google Patents

Description

L. SHEPHERD.

METHOD OF MAKING LEAD ARSENATE. APPLICATION FILED OCT-14,1911.

H 1,175,565., Patented Mar. 14,1916.

WlTNESSE5- INVENT R- w?amm 0.

ATTORNEY- tions in this process have LEE SHEPHERD, OE CLEVELAND, OHIO, ASSIGNOR T0 THE'HARSHAW, FULLER & GOODWIN COMPANY, OF CLEVELAND, OHIO, A CORPORATION OF OHIO.

mnrnon or Max ne LEAD ARSENATE Specification of Letters Patent.

Patented Mar. 14, 1916.

Application filed October 14, 1911. Serial No. 654,626.

To all whom itmay concern:

Be it known that I, LEE SHEPHERD, a citizen of the United States, and a resident :of Cleveland, county of Cuyahoga, and State of Ohio, have invented a new and useful Improvement in Methods of MakingLead Arsenate, of which the following is a specification, the principle of the invention being herein explained and the best mode in which I have contemplated applying that principle, so as to distinguish it from other inventions.

- The ordinary method of manufacturing lead arsenate has been by a so-called wet process, wherein, for example, a soluble arsenate is caused to react with a suitable lead compound so as to precipitate the relatively insoluble lead arsenate. Various modificaarisen depending upon the character of the salts used, but all are alike objectionable in that solutions more or less dilute in character have to be dealt with, and that the lead arsenate, when finally formed, must be separated or filtered out of a solution with attendant delay. I am aware that it has been attempted to avoid the objectionable features of such wet processes by roasting combining weights of white arsenic and a suitable lead compound in the presence of oxygen so as to produce the lead arsenate at a single operation. A number of dilficulties, however, likewise attend this method of treatment, especially if a relatively pure arsenate is desired, and this is more or less essential, at least so far as any admixture of arsenic in the resulting product is concerned.

The object of the present invention, accordingly, is the production of such arsenate by directly 'combining'white arsemc with a suitable lead compound in such away as to insure the reaction being a complete one, as

also' to permitthe proper proportions of the entering materials to be readily maintained at all times. v

To the accomplishment of the foregoing and related ends, .the invention, then, consists of the steps hereinafter described and particularly pointed out in the claims.

The annexed drawing andthe following description set forth in detail various approved, methods of carrying out the invention, such disclosed modes, however, cons tube of the blow pipe,

stituting but several of the ways in which the principle of the invention may be used.

In said annexed drawing :-Figure 1 represents diagrammatically a vertical section of a suitable apparatus for carrying on the present improved process; and Fig. 2 is a plan view, partly in section of a modification in construction.

My improved process is a continuous one and may be briefly described as consisting in burning ingas, under proper conditions, a, suitable mixture of either metallic lead or a lead compound, along with white arsenic. Preferably lead sulfid, which is obtainable in practically pure form as the ordinary galena ore concentrate, is employed, not only because it is obviously cheaper than the metal, which has to be smelted from such. ore, but also because the sulfur constituent, being combustible, will actually contributeto the maintenance of the temperature required for the reaction between the lead and the arsenic. The latter is the ordinary white arsenic of commerce. While it is preferred to use natural gas for burning the lead and arsenic, on account of its cheapness and heat value, other gases can of course be used.

The white arsenic in commercial form is, of course, already a fine powder, and in order to prepare the lead sulfid ore for use in the present process, it likewise is ground exceedingly fine, such grinding being best done by the air flotation method, which does not require to be described in detail. The ground ore and white arsenic are then intimately mixed in the proper proportion, such In order to eifect'the combustion of the two ingredientsjust described, the mixture formed thereof is charged into a feeding hopper 1 (Fig. 1), provided with a screw 2 or other feed device, by means of which it may be continuously fed into the air et 3 of a blow pipe. Air is forced through such jet by a blower 4, while a p1pe'5 surrounding the jet so as to form the outer is connected with I White arsenic. The products of the combustion are pro ecte'd into a combustion chamber 7. which may consist of any material not affected by the intense heat or attacked by the products of the combustion. Thus it may be constructed of iron or suitable brick, but if of the latter, the brick must not contain silica or other compound capable of entering into combination with the lead, so as to be fused. Magnesite or chrome brick are suitable materials for this purpose. A. hopper or receptacle opens into the fioorof chamber 7, in order to receive any incombustible earthy materials which may be mingledwith the lead sulfid ore. Coextensive with'the combustion chamber, as it has been'termed, is an extension or flue 9, which is shown as being constructed of brick (brick of the kind just described being of course used for this purpose), although it may be of iron, as the combustion chamber proper; or both combustion chamber, and this extension, or continuation thereof, maybe of brickin the form of a single compartment 10, as shown in Fig. 2. External heat. may be applied to this extension of the chamber, as by burners 11, in order to initially raise the same to the proper temperature, or to assist in maintainmg such temperature, if it is not desirable to lntroduce enough gas in the Initial combustion step to heat the entire compartment."

'result presently to be set forth.

Connected with the furnace, as I shall 1 term the complete combustion chamber, with its extension, is a cooling pipe 12,-preferably of metal and of such length and so constructed to cool the fumes resulting from the combustion in the former sufliciently to enable them to be passed through one or morev separators or dust collectors 13 in which any solid product may be deposited. A final separation of such product is efiiected by means of bag filters 14 of-well I known construction.

The circulation of air through the apparatus is accomplished by means of a fan 15 placed at a suitable point in such apparatus, being shown as located after the bag filters last referred to. The exhaust gases from He filters, whether 'forced or sucked therethrough are preferably discharged into a-stack 16.

The products of the combustion occurring at the entrance to the furnace are probably in ,the state of .vapors and may be con,-

'--'*'si'de'redas consisti ng of lead arsenate and ll-j had arsenite, as le d. xithfll'fifimiqlls oxid (AS203) and arsenic oxid (AS205), the sulfur in the ore being of course, converted into sulfur dioxid (S0 which is a gas. A high temperature, approximating that at which this combustion takes place, is maintained long enough for these "apors, or products of combustion whatever their character, to'completely react, the result of such reaction, disregarding the sulfur dioxid, being lead arsenate, where the lead sulfid and White arsenic are mixed together in the proper proportions, and sufficient air is admixed with the gas. -This lead arsenate settles in the cooling pipe, the dust collectors and the filter bags, from which'it may be removed at'intervals. It is an extremely finely divided White powder, very light in gravity and can be used in this condition or be mixed with water to form a paste, if more conveniently handled in the latter form. The term lead arsenate as here used, is of course intended to designate the commercial product and not any one specific lead arsenate, commercial lead arsenate usually consisting of. a mixture of two chemically difi erent lead arsenates as is Well known.

It has already "been indicated that in place of lead sulfid, metallic lead or any suitable compound of the metal such as the oxid, carbonate, or'basic carbonate may be used, although the advantage in employing the sulfid over any of these should be obvious. The process in hand is also applicable to the making of other metallic arsenates than lead arsenate, such for example as iron arsenate and copper arsenate. Where an oxid, or oxygen yielding com-pound is employed, the oxidizing of the arsenic is assisted, and instead of depending upon the oxygen from the air or the lead compound for this purpose, some oxidizing material such as niter may be introduced along with the lead and arsenic mixture. The process, likewise is not limited to use of the specific compound of arsenic, viz., white arsenic, that is named; but the higher oxid can be employed if found commercially expedient.

The combustion step, furthermore, may be assisted by heating the air which is introduced through the burner.

In conclusion it may be remarked that it is quite possible, instead of intermixing then introduce them into a heated chamber or furnace. This in fact is the arrangement illustrated in Fig. 2, where two hoppers 1 and associated burners 17 are arranged to discharge into the furnace 10. The feeding that prerieas ydescr bes. n gard regards the process to the terms burning and combustion, as herein used, it should be explained that the exact character of the phenomena attending the ignition of the intermingled streams of gas and air discharged from the burner, along with the powdered lead and arsenic borne by such gas and air, is diliicult to ascertain. These terms are hence not to be understood as being necessarily employed in a strictly literal sense, but to include either an actual oxidation of any of the ingredients or their simple vaporization. i

Other modes of applying the principle of my invention may be employed instead of the one explained, change being made as herein disclosed, provided the step or steps stated by any one of the following claims or the equivalent of such stated step or steps be employed.

I therefore particularly point out and distinctly claim as my invention 1. The method of making lead arsenate, which consists in burning together a combining. mixture of a lead compound and an arsenic compound in the presence of air, whereby the products of their combustion v are. intermingled; and then cooling such products. a

2. The method of making lead arsenate, which consists in burning together a combining mixture of a lead compound and white arsenic in the presence of air; whereby the products of their combustion are intermingled; and then cooling such products.

3. The method of making lead arsenate, which consists in burning together a combining mixture of lead sulfid and white arsenic, both in finely divided state, in the presence of air; and then cooling such products.

4. The method of making lead arsenate, which consists in discharging an ignited combustible mixture of a lead compound, an arsenic compound and a hydro-carbon fuel into a highly heated chamber; and then cooling the products of the resulting combustion.

5. The method of making lead arsenate, which consists in discharglng an ignited combustible mixture, consisting of a suitable lead compound, white arsenic and hydro-carbon fuel, into a highly heated chamber; and then cooling resulting combustion.

6. The method of making lead arsenate, which consists in discharging an ignited combustible mixture, consisting of lead sulfid and white arsenic, both in a finely divided state together with a hydro-carbon fuel, into a highly heated chamber; and then cooling the products of the resulting combustion. I

7. The'method of making lead arsenate, which consists in discharging an ignited combustible mixture, consisting of lead sulfid and white arsenic, both in a finely divided state, together with natural gas, into a highly heated chamber; and then cooling the products of the resulting combination.

Signed by me this 12th day of October,

LEE SHEPHERD. Attested by- ANNA L. GILL, JNo. F. OBERLIN.

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