Recent improvements in the practice of milling lead ores of the Southeast Missouri Lead Mining District has resulted in the production of low-grade mill tailings. The tenor of the lead in the tailings is often between 0.05 and 0.25 per cent. In view of the fact that large tonnages are handled daily and that further improvements are under way, it is imperative that the lead content of these tailings be accurately determined.
For this purpose an electrolytic board, which speeds up the electrolytic determination of lead in low-grade mill tailings, has been devised at the Mississippi Valley Experiment Station of the United States Bureau of Mines, in cooperation with the Missouri School of Mines and Metallurgy, Rolla, Missouri.
The electrolytic board is the result of several years work in cooperation with large lead mining companies. The method employed in the determination of small amounts of lead has been included as well as certain precautionary measures --Introduction, page 1

Holmes, O. W.

English

Missouri University of Science and Technology (Missouri S&T): Scholars' Mine

Scholars' Mine Professional Degree Theses Student Theses and Dissertations 1929 Electrolytic board for the determination of lead, and some comments on the procedure for lead in low-grade tailings of the Southeast Missouri Lead District O. W. Holmes Follow this and additional works at: https://scholarsmine.mst.edu/professional_theses  Part of the Chemical Engineering Commons Department: Recommended Citation Holmes, O. W., "Electrolytic board for the determination of lead, and some comments on the procedure for lead in low-grade tailings of the Southeast Missouri Lead District" (1929). Professional Degree Theses. 297. https://scholarsmine.mst.edu/professional_theses/297 This Thesis - Open Access is brought to you for free and open access by Scholars' Mine. It has been accepted for inclusion in Professional Degree Theses by an authorized administrator of Scholars' Mine. This work is protected by U. S. Copyright Law. Unauthorized use including reproduction for redistribution requires the permission of the copyright holder. For more information, please contact scholarsmine@mst.edu. EIECTROL'YTIC BOABD FOR TEE DETERMINATION OF LEAD, .AND SOME COMMENTS ON THE PROCEDURE FOR !FAD Il~ I.Ow-GRADE TAILilrGS OF THE SOUTHEAST MISSa:rnI LEAD DISTRICT. -By-Oliver Wendell Holmes. A THESIS submitted to the Faculty of the SCHOOL OF MINFS .AND METAILURGY OF THE UNIVERSITY OF MISSCXJRI in tulfillment of the wark required for the Degree of CHEMIC.AL l!NGINEER. Rolla, Missairi, 1 9 2 9. 35705 Approved: (d(Ef;fiLPvtJJ Pro essor of Chemistry. T.ABIE OF CONTmTS. Preface • • • • • • • • • • • • • • • • • • Aolmowled.gments • • • • • • • • • • Introduction • • • • • • • • • • • • • • • • • • • • • • • • • Apparatus • Method • • • • • • General Disoussion Precautions • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • •• • • Accuracy Copper • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • Cost and Upkeep • • • • • • • • • • • • • • • Summary • • • • • • • • • • • • • • • • • • • • • • • • Conclusions • Bibliography • • • • • • • • • • • • • • • • • • • • •• • • • • • • • • • • • • • • • • • General Index • • • • • • • • • • • • • • • • • • • -1-Page ii ii 1 2 4 5 5 7 7 9 g 10 ll 12 This thesis is presented to the Faculty of the Missouri School of Mines and Matallurgy 1n fUltillment of the work required for the degree of Chemical Engineer. The results reported herein are the direct outgrowth of exISrience obtained during the crurse of milling research on the lead ores of the Southeast Miss01ri Lead Belt for the last three years. This research has been carried on by the Mississippi Val-ley Experiment Station of the United States Bureau of Mines, mrk-ins in cooperation with the Miasruri School of Mines and Metal-lurgy, Rolla, Missouri. ACKNOWIEOOMEN'IS. Acknowledgments are due Mr. William Kahlbaum; 1'onnerly Assistant Metallurgist, U. S. Bureau 01' Mines for his assistance in the construction of the electrolytic board; to Mr. Will H. Coghill and :r. B. Clemmer, Supervising Engineer and Junior Metal-lurgist of the Mississippi Valley Station of the Bureau of :Mines, respectively, for their ccnstructive criticism; to Mr. D. P. Morgan, Junior Chemist of tm sane station; and to Dr. w. T. Schrenk, Professor of Chemistry at the Missouri School of Mines and Metallurgy f'or tmir helpful suggestions and advice in tbe preparation of the manuscript. - ii-EtECTROLITIC BOABD !OR THE DETERMINATION OF IEAD, AND SCUE COMMENTS CN THE PROCEOORE FOR L'EAD m LOW-GRADE TAILINGS OF THE SCJUTEEAST MISSOURI lE.AD DISTRICT. -By-o. w. Holmes. INTROIDCTION. Recent improvemnts in the practice of milling lead ores ot the Southeast Missouri Lead Mining District has resulted in the production ot low-grade mill tailings. The tenor ot the lead in the tailings is often between o.o5 end 0.25 per cent. In view of the fact that large tonnages are handled daily and that further improvements are under wey, 1 t is imperative that the lead con-tent of these tailings be accurately determined. l'or this purpose an electrolytic board, which speeds up the electrolytic determination ot lead in low-grade mill tailings, has been devised at the Mississippi Valley Experiment Staticm. ot the United States Bureau of Mines, in cooperation with the Missouri School ot Mines and Metallurgy, Rolla, W.ssouri. The electrolytic board is the result of' several years wark in cooperation with large lead mining canpanies. The method employed in the detennination of smell aJIDunts of lead has been in-cluded as well as certain precautiollary measures. -1-APPARA'IUS. The apparatus used is a modi f.i. cation of the Guess-Hau1-tain cabinet, and is so arranged that 24 leads, or 24 coppers, or n2 leads and 12 coppers may be run simultaneously. A photograph of the cabinet is slx>wn in Figure 1, the details of which are given in the appended drawing. It lla.s two rows of 12 cells each, one above the otmr, and any cell n:e.y be removed fran the circuit without disturbing the others. Staticnary anodes and cathodes are used. The anode is .made of sand-blasted corrugated sheet plati-num. The dimnsions of the corrugated anode are 6 by 3 centimeters. Each cell contains two platinum foil cathodes, 8.4 by 0.3 centi-meters. The electrode lx>lders are made of aluminum, and extend horizon tally :f'ran the surface of the cabinet. When the electrodes are in place a 150 ml. beaker of regular fo:tm with lip, containing the electrolyte my be put in place and the lIX>veable beaker-rest pulled out. W~n it is desired to remove an anode while a series of determinations is being made, the removal is accomplismd in the following manner: e beaker support is slipped back into the cabinet, the knife switch corresponding to the cell is closed, and simul-taneously, the beaker conta:fning ttle electrolyte is lowered and removed. The anode may then be removed and treated in the usual manner. -2-Figure 1. View of Electrolytic Board. - 2-A-The cabinet ccntains as an integral part, a recording ammeter of 0 to 5 amperes capacity for overnight determinations of copper. .Anotmr snail ammeter with a range ot o to 6 amperes is incorporated in the apparatus for lead work. By ~ans of catveniently arral'8ed swi tobas a line cur-rent of 220 volts, D. c., may be thrown into any series of cells and the amperage recorded on the des ired ammeter. The am_perage may be adjusted by means of a variable resistance using either a rheostat or a bank of carbon lamps. The aluminum electrode holders were originally 2-718 inches by 3 I 8 inch at the base, ta:parillg to l f 4 inch at the end. These were cast in a carbon block mould, and later the base ma-chined to l( 4 inch. The e lactrode lx>lders are riveted to alumi-num. plates for connecticn at the back of the cabinet face. They were cut lengtbvise thrrugh the middle to a depth of 1-518 inches and then cut fran tbe side tmtil one of the pieces- tell away. When in service the pieces are l:eld together by gmn rubber tub-ing slipped over them they make a clamp that holds the electrodes firmly when inserted in the slit. The wires are protected tram tum.es by placing them behind the cabinet face. The apparatus is a modification of those used in the Soutl:east Missouri Lead Belt. It incorporates new ideas and de-tails, which simplify the manipulation. -3-ME'!HOD. The custan.ary- procedure is as follows: In this method it is ccnvenient to weigh one or more factor weights" of the sanple, depending upon the lead content. When tm lead content of the sanple does not exceed two per cent, two or m:>re factor weights are used; wben it is fran two to seven per cent, one factor weight is used. If the sample caita:ins over seven per cent lead the mlybdate method is to be recommended. The theoretical factor for converting lead dioxide to lead is 0.856. Weigh the aDDunt of sample decided upon into a 150 ml. beamr. Add 25 ml.. of nitric acid (d 1.4), heat until the evolution of brown tumes has ceased. Wash down the sides of tbe beaker with water and add 15 to 20 ml. of a solution ot ammonium nitrate, made by dissolving one pound of the chemically pure salt in two 11 tars of distilled water. Dilute the electrolyte to abcut 145 ml. Electrolyze tor two hours at a tenperature of 70 to 00° c., with a current density of two amperes e.nd a poten-tial of 3.5 volts. -4-GENERAL DISCUSSION. When interferiDg elements are absent electro:cysis may extend overnight at 0.2 8JI!Peres. When the lead cmtent of the electrolyte is less than ten milligrams, 25 ml. of a solution of lead nitrate, containing the equivalent of 0.00048 gram of lead dioxide per ml. , should be added bef'om electrolysis. Tbe addition of the solution of lead Di trate is to increase the lead con tent to the point where mexinmm deposition is obtainable. Experiment has shown that the results are more satisfactory wmn the electrolyte contains the equivalent of 12 to 80 milligram of lead dioxide. It is neces-sary to take certain precautions to insure best results. PRECAUTIONS. This method cennot be used with a high degree or accur-acy when the electrolyte caitains more than 0.03 gram of man-ganese. The quantity of' mexiganeae may be regulated by reduc :1ng the size of the sa~le. The detrimntal effect of man~nese will then be overcane by the presence of the given amount of' free ni-tric acid in the electrolyte. In no case should the concentration ot tree nitric acid in the electrolyte exceed 15 per cent by vol-ume. The presence of mangamse in a sample prevents electrolysis at low current demity for a long period of time. The manganese would deposit w 1th the lead. -5-Copper, iron, and zinc do not interfere with t~ depo-sition of lead. Antimony and bismuth, when pxesent, would likely have to be com.batted in the sams manner as manganese, tln t is, by reduc :ing the size of the sanple taken far analysis; no recent ex-perience bas been encountered with antimony and bismuth. Arsenic must be removed before electrolysis. The acidity of the electrolyte has a very important ef-fect upon the deposition of the lead dioxide. E~erience has s}J)wn that 15 per ce~t by volume of nitric acid (d 1.4) is neces-sary for the best results. Erratic results are obtained when the acid concentration varies far fran this value. Before electrolysis the anodes are cl.a aned by immersing in a dilute solution of nitric e.rd oxalic acids. They are tilen brushed with a camel hair brush, rinsed with distilled water, igni tad to constant weight in the flame a! a Fisher burner, cooled in a desiccator, and weighed. After electrolysis is complete the anode is detached and immediately immersed in a beaker of distilled water. It is dipped consecutively into two beakers containing ethyl alcohol. The anode is rem:>ved tran the beaker and the alcohol bumed off, keeping the anode in motion to p mvent the alteration oft m de-posit. Cool in a desiccator and weigh. -6-ACCURACY. It has been :round that this method o:r electrolytic recove17 o:r the lead in mill tailings is the best for mill practice when the time element is standardized. But research has to be done to determine its accuracy. Because of the simplified procedure and the small num-ber o:r steps necessary, the electrolytic method is mch to be desired over others. In tact it is possible to accomplish more detenninatians with a high degree of accuracy in less time tban when any other method is employed. A number ar mill tailing samples were analyzed by the author and a chemist ot the National Lead Company ot St. Francois, Missouri. The results obtained by using this method are given in Table I. COPPER. The apparatus as given for lead determinatioDS is also adapted to, am suitable tor, the determination of copper. The method employed is the stanlard procedure for elec-tro~ic copper. The apparatus 1 s not the type generally em-ployed tor such wolit, but highly accurate results are obtainable by overnight deposition. -7-Table I. Comparison of Results. Assay Per cent Lead Sample Results obtain- Results Difference Number ed by National obtained Lead Canpany• s by the Chemist author 1 o.oe 0.075 0.005 2 0.10 0.095 o.oos 3 0.10 o.o9s 0.002 4 o.7o o.7o - -5 o.52 o.52 - -6 o.44 0.45 0.010 7 0.40 o.39 0.010 8 0.30 0.31 0.010 9 0.30 0.29 0.010 10 0.09 a.as 0.010 11 0.04 o.o5 0.010 12 0.045 0.06 0.015 13 0.04 o.05 0.010 -8-COST AND UPKEEP. The first cost ot such an apparatus is high, but there-after the ma:ln expense is for the current consumed in operation. It needs but 1i ttle care and will last indefinitely. SUMMARY. It is desirable to keep the following points in mind in order that the highest degree or accuracy may be obtained. 1. The size of the sanple taken de:pends not only on the lead cai.tent of the ore but on the manganese content a.s well. 2. Maximum recovery is not possible when the lead con tent of tm solution is below 12 milligrams Pb0 2 • 3. Low results are obtained when the solution contains more than 70 milligrams of lead, because the deposit flakes off. 4. Manganese is deposited very readily from solutions when a low current density is em-ployed. 5. Practically complete deposition of lead from pure solutions is obtained by using low cur-rent densities for long periods of time. -9-6. Current densities of 2 to 3 amperes for a period of two hours is sufficient for low-grade materials; electrolysis for two hours is a good starxlard. 7. The electrodes should be sand-blasted oc-casionally to f'acilitate the adherence of the deposit. CONCLUSIONS. In view of tm fact that the electrolytic method for tm determination of lead is mpid and accurate, it is to be preferred over gravimetric netbods whenever it can be applied, or whenever a large number of determinations are to be made. - 10 -B I B L I 0 G R A P H Y. ------------Benner, R. c., The Rapid Detennination of Lead in Ores by Elec-trolysis with Stationary Electrodes; jour. Ind. Eng. Chem., Vol. 2, PP• 348-9. Benner, R. c., New Form Gauze Electrodes for the Rapid Electro-lytic Determination of Lead and Copper. Met. & Chem. Eng., Vol. 9, PP• 141-5. Fairchild, jobn G., Some New Features in the Electrolytic Determinaticn of Lead. J"our. Ind. Eng. Cmm., Vol. 3, P• 902. Hughes, w. E., The Electrodeposition of Metals, Vol. VIII, Lead. Bema, Vol. 9, pp. 555-62, 1921. Chem. Abstracts, Vol. 15, P• 3250. Sand, H. J. s., The Rapid Electroanalytical Deposi ticn and Sep-aration of Metals, Part I. J'our. Cbml. soc., PP• 91-2, 373-410, March, 1907. Sand, H. J. s. , The Electroanalytical Determination of Lead as Peroxide. Chem. News, Vol. 100, pp. 269-70. Smith, Edgar F., Electro-cmmical Analysis., Third edition; P. Blakinston's Son&. Co., Philadelphia, 1902. Vortwrnn, G., The Electrolytic Determination of Lead. Annalen, Vol. 351, 00. 283-93, 1907. Westerkamp, A., Electrolytic Determination of Lead in Tin-Lead Alloys end Tin Plates. Arch. Pham.., Vol. 245, pp. 132,.g. Woiciechowsld., B., Electrolytic Determination of Lead in Large and Small Am>tmts Using a Gauze Cylinder Anode. Met. & Chem. Eng. , Vol. 10, P• 108. - 11-GENERAL DIDEX. Accuracy • • • • • • • • • • • Acidity •• Acknowledgments • • • • • Ammeters • • • • • .Ammonium nitrate solution • • Anode cleaning • • • • • • • construction weighing • • • • •• • • Antimony •••••• • • Arsenic • • • • • • • • • • • • • • • Bismuth • • • • • • • • • • Blueprint • • • • • • • Cathode construction • • • • • • • • • • • • • • Comparis en of Anazyses, Table I Cone lusi ans • • • Conditions of electrolysis • • • Copper • • • • • • • Cost and Upkeep Deter.mina.tia:i of Co~per Electrode holders • • • • • • Factor • • • • • • • • • • • • • • • • • • • • • • • Guess-Haulta:in Cabinet • • • • Iron • • • • • • • • • • ••• 1ead nitrate solution Mallgamae • Method • • • • • • • • • • • • • • • • • Removal of anodes fran circuit s unmia.ry • • • • • • • • • • • Tenor of mill tailings • • • Zinc • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • -12-• • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • Page 7 5 ii 5 4 6 2 6 6 6 6 Appended 2 8 10 4 6 9 7 3 4 2 6 4 5 4 2 9 1 6 

Electrolytic board for the determination of lead, and some comments on the procedure for lead in low-grade tailings of the Southeast Missouri Lead District

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Electrolytic board for the determination of lead, and some comments on the procedure for lead in low-grade tailings of the Southeast Missouri Lead District

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