Document Rjj48Y29939nGpXqXLqrpMKpV

Patented Feb. 16, 1932 1,845,7B3T UNITED STATES PATENT OFFICE GUNNABD E. JOHNSON, OF EAST CHICAGO, REGINALD G. BOWMAN, OF GABY, AND WILLIAM J. KNOX, JR., OF- HAMMOND, INDIANA, ASSIGNORS TO ANACONDA LEAD PRODUCTS COMPANY, OF BAST CHICAGO, INDIANA, A CORPORATION OF DELA WARE METHOD OF PRODUCING WHITE LEAD No Braving. Application 51*4 Janaary 1' r, 1951.. Serial No. 509,534. This invention relates to improvements in .trollingthe bicarbonate content of the anolyte the electrolytic process of producing white might readily be devised, the foregoing being lead and is more particularly concerned with suggested merely as examples. certain refinements in the control of the ,proc- In; the second place we have found that the g ess whereby we are enabled to predetermine carbonate salt content of the anolyte must M * the Character or quality of white lead formed be kept low--much lower than is required, in and to accurately control, in continuous op order to avoid formation of white lead in eration-, the conditions* which are1 essential to crustations on the* anode--in order to pemdt the production of the desired product. washing the white lead free of these sahs hi 10 In the United States patent to Ralph M. the finishing of tfie*white lead separated from ^ Harrington, No. 1,308,948, it is recognized the anolyte-. This is important in the coim that the character and quality of the white merciai production of white lead by the elem lead product may be controlled by regulating trolytic method, since the presence of any the amount of carbon dioxide supplied to the considerable amount of alkali metal car jj catholyte, and it is further recognized that in bonate in the white lead product renders it & order to obtain rapid carbon; dioxide absorp unfit for -use- aa paint pigment. We have tion and at the same time avoid precipitation found that the difficulty in washing the white of white lead on the anode*, it is' necessary lead1 sufficiently free of adsorbed salts in to maintain the catholyte as compared with creases with increasing concentration of car- the anolyte relatively strohgly alkaline.; ^ bonate salfc in ,the: anolyte to a point at which ru In- the operation of the.Harrington proeess it. is practically impossible to eliminate them. on a commercial scale and for a period of This may be explained by adsorption of the years we haveencountered certain difficulties salts in the white lead particles, but it seems and have worked: out certain refinements of more probable that a reaction may occur as as control for overcoming such difficulties, follow8: * which1 refinements constitute! the subject mat ter of the present invention. In. the first place we have found chat the 2 (2PbCO*-Pb (OH) 2) +Na,CO,+ NaHCOi-- 3NaPb2 (CO*) 2OH+H*0 composition of the white lead produced varies whereby the carbonate salt becomes chemical 39 direct]^ with the HCOt ion or bicarbonate ly combined: and therefore very difficult'or 99 content of the anolyte. By virtue of this impossible to remove. disctijjeey we are enabled to more accurately In accordance with/our invention, using a and mfeButaently control <the composition, of bi-fluid cell with a lead anode suspended in the iHliftfrlead produced and to bring about the anolyte capable of yielding a solvent for as such-control in a variety of ways, i. e., by any the lead,.* g., sodium acetate*. and/ a suitable si method which may serve' to influence the inert cathode suspended in the catholyte con HCO, ion content of the anolyte. e. g. (1) by taining sodium carbonate and separated from controlling the supply of C|p* to the catholyte the anolyte by a suitable diaphragm, and to as described in the Harrington patent, (2) which Ct)* is supplied; ail as. disclosed in the 10 by maintaining the supply of C02 to the above mentioned Harrington' patentj the ano- 99 catholyte constant ondi adding acetic acid to lyts solution is sampled and analyzed at reg the anolyte at a point outside the cell, (3) by ular intervals, say every hour; and its bicar maintaining the supply of'CCh to the cath bonate content adjusted to and maintained at olyte constant and subjecting the anolyte to the desired figure fly anysuitablemethod such a an extra electrolytic treatment to convert its as one of'those referred to above. 99 sodium acetate content into bicarbonate, and For example, h e a cell operated at a cur (4) maintaining the supply of C02 to the rent density of 30 amperes per square foot of catholyte constant and supplying sodium bi cathode area and producing approximately carbonate as such to the anolyte at a point .011 pounds of.whole lead per ampere hour 5# outside the cell. Still other' methods of con- andii oparlaringi\aA4 aiy azrolyter displacement 109 N11534 PNYC00009557 fyW-. i 2 1,845,713 rate of 18 gallons per minute, the sodium of OH to HCOs ions transferred to the ano bicarbonate content of the anolyte is main lyte from the catholyte through the dia tained at .0561% to produce a wh'ite lead con phragm which in turn is controlled by control taining 11.60% of CO,. To produce white of the carbonation of the catholyte and/or by - lead of greater or smaller CO- content the one of the other methods above referred to for acid carbonate content is increased or de controlling the bicarbonate content of the creased,respectively, the exact acid carbonate anolyte or suitable combinations thereof or content required: for the production of a par other methods which may be devised. ticular white lead, product being' determined We claim: ;9 in each instance by experiment. The car- 1. In the process of producing white lead I* ' bonate salt content of the anolyte is main by electrolysis in a bifluid cell, in which the tained at not exceeding about twenty-five wnite lead is precipitated in an.anolyte ca- one-hundredths of one percent, (0.25%) and patle under electrolysis of yielding a lead sol preferably in the neighborhood of six one- vent and containing bicarbonate salt the steps 3 hini}red|hs:,.:(ifhhe'percept! :|0,()6%.),.. 1'he which consist in determining the bicarbonate 88 significance of the limited carbonate salt con concentration in the: anolyte corresponding tent of the anolyte specified .rnay be appre to the precipitation of white lead of the de ciated by comparison with 'the limitation of sired composition, and maintaining said bi tfeilla^dni^sijii;1 content ib|, fheijabolyte, neC- carbonate content in the anolyte by maintain ing a uniform and deficient carbonation of 88 'whBb 'lieS:d:!:cii|!:.ip^::!aho(ie: in accordance with the catholyte and adding an acid to the the Harrington patent. .In this case the car anolyte. 1 bonate salt content of the anolyte may run 2.- In the process of producing whit*, lead a| 'felija^sixiflhth^bf:bnje.jbes'fe|nlt (:040!%;)) by electrolysis1 in S' bifluid .cell in which the ,85 which cohteiit. however, will produce white white leads is1 precipitated in an anolyte ca- 80 lead containing so much carbonate salt that pable under electrolysis of yielding a lead solit is not feasible m commercial operation to ` vent and containing bicarbonate salt the steps wash it sufficiently free of such salt as to which consist in determining the bicarbonate produce a first grade white lead paint pig- concentration in the anolyte corresponding to ,30 ment. the .precipitation of white lead of the desired 88 , _\= als pren -tatH. th* t--" p-ir-'P-d points ipnippSltiion,! fzjjjd' maintaining said bicarbon of irlin-im nt of the prim'" "h-i .-bed in the ate content in |hp(;anoiyte!.:t>y maintaining a Harnngton patent constituting the present Utijiylpip 'knd||:defi<|Ijitj: carbonation of the invention are (1) limiting the carbonatesalt i.ghdrMdih^ :'a tuGi^bOnhte to the 35 content of the anolyte to a predetermined anolyte. maximum to permit trie substantially.epfij; hte uro val of -ucn -alt i-nm *1 e precipitate.i white lead and the production of a a lute lead pigment su.table for use as a paint 40 pigm-r.t, and C2) control of the composition nf'tli wmte lead bv reference to the bicar In testimony whereof, we affix our signa tures:.!' GUNNARD E. JOHNSON. REGINALD G. BOWMAN. WILLIAM J. KNOX, Jb. 108 bonate content of the anolyte In explana- t on of the last named refinement it may be 'aid 'hat the white lead formation s repre- 45 sente-1 by the following reaction equation. JPbCaH,0,),+ra,CO,-i-2H.0= SlPbC!<3^.Pb(OH)i+2NaIICO, -,X iC,U,0, Thitomposition of the tasic lead salt pre- 50 cip-tnted varies with the pH value of the solu tion in which it is formed. It will lie appar ent. therefore, that if only Na.COi and Phi0-11,0,), were supplu-d to the solution, the N allC O, content would progressively in- 55 reaie- and the ratio of HCO, to OH ions in the resulting precipitated lead salt would increas3 until finally only PbOO, would be pro duced. In other worcls the COj content of the precipitated white lead bears a direct rela- ,49 tin to th*8 Nh HCO, ''oncentrat m or the molvte This has been found to be true m .Lctua) operation. In order to control the com posit on (if the white lead p> educed therefore, it ib necessary to control tno XallCO* content .of the anolyte, e. g., by controlling the ratio 115 120 125 m PNtcooo 09558