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 Electrolytic Separations Possible With 
 a Rotating Anode 
 
 JTHESIS 
 
 Presented to the Faculty of the Department of Philosophy of the 
 
 University of Pennsylvania, in Partial Fulfilment of the 
 
 Requirements for the Degree of 
 
 Doctor of Philosophy, 
 
 BY 
 DONALD S. ASHBROOK, 
 
 PHILADELPHIA, PA. 
 1904 
 
 PHILADELPHIA 
 
 THE JOHN C. WINSTON CO. 
 
 1904 
 
Electrolytic Separations Possible With 
 a Rotating: Anode 
 
 THESIS 
 
 Presented to the Faculty of the Department of Philosophy of the 
 
 University of Pennsylvania, in Partial Fulfilment of the 
 
 Requirements for the Degree of 
 
 Doctor of Philosophy, 
 
 BY 
 DONALD S. ASHBROOK, 
 
 PHILADELPHIA, PA. 
 1904 
 
 ^e; 
 
 . 
 
 PHILADELPHIA 
 
 THE JOHN C. WINSTON CO. 
 
 1904 
 
cto 
 
 5 
 
 This work was undertaken at the suggestion of Dr. 
 Edgar F. Smith. The author takes this opportunity 
 to thank him for his many kindnesses and personal 
 interest during the six years in which he has been a 
 student. 
 
INTRODUCTION. 
 
 A year ago, Exner* working in this laboratory demon- 
 strated that by using a high current density and great 
 pressure with a rotating anode it was possible to deter- 
 mine fourteen metals in the electrolytic manner much 
 more rapidly than had ever been done previously The 
 deposits were in all instances most satisfactory. These 
 results constituted an important advance in electro- 
 chemical analysis. The objection once put forward, that 
 too much time was necessary in such work, was com- 
 pletely removed. Indeed Exner's investigation has 
 wholly revolutionized electro-analysis. However, there 
 remained the question as to how far this procedure would 
 lend itself to the separations of the several metals. This 
 point became the guiding thought in the investigation 
 here presented. 
 
 The apparatus and method of procedure have been 
 fully described and amply developed by Exner, so that 
 they need not be again entered upon, but the separations 
 which were successful and have value will now be described 
 in such detail as to guide all persons who may be desirous 
 of repeating them. 
 
 * Jour. Am. Ch. Soc., Vol. XXV, p. 896. 
 
 173155 
 
EXPERIMENTAL PART. 
 
 COPPER. 
 i. FROM ALUMINIUM. 
 
 (a) In sulphuric acid solution. Dilution 125 cc., o.i cc. 
 of sulphuric acid (Sp. G. 1.83), N.D IOO = 4-5 amperes 
 and 14 8 volts. Time 10 minutes. 
 
 Copper present 0.2696 gram, aluminium 0.2500 gram. 
 Copper found 0.2696 gram-o.2696 gram-o.2695 gram. 
 
 Like all deposits from this electrolyte they were some- 
 what spongy but perfectly adherent. On increasing the 
 amount of sulphuric acid to i cc. the deposit was much 
 smoother and more uniform. 
 
 (b) In nitric acid solution. Dilution 125 cc., i cc. of 
 nitric acid (Sp. G. 1.43), N. D IOO = 3 amperes and 4-5 
 volts. Time 20 minutes. 
 
 Copper present 0.2874 gram, aluminium 0.2500 gram. 
 Copper found 0.2873 gram-o.2874 gram-o.2874 gram. 
 
 The conditions given here were most satisfactory for 
 copper in this electrolyte. A speed of 300-400 revolutions 
 per minute is best. Too high a speed or less time gives a 
 low result. 
 
 (c) In phosphoric acid solution. Dilution 125 cc., 10 cc. 
 of phosphoric acid (Sp. G. 1.085), 50 cc. of a 10% solution 
 of Na2HPO4, N.D IOO = 5 amperes and 6 volts. Time 10 
 minutes. 
 
 Copper present 0.2742 gram, aluminium 0.2500 gram. 
 Copper found 0.2741 gram-o.2742 gram-o.274i gram. 
 
 The conditions recorded here gave the best deposits. 
 They were spongy in appearance but perfectly adherent 
 and were washed with ease. On dissolving them in nitric 
 acid and testing with an ammonium molybdate solution, 
 a slight deposit of ammonium phospho-molybdate was 
 
 (5) 
 
obtained in every case. This amount of phosphorus was 
 so slight, however, that it would not affect the weight of 
 the deposit materially. 
 
 2. FROM ANTIMONY. 
 
 (a) In tartrate solution. Dilution 125 cc., 8 grams of 
 tartaric acid, 25 cc. of ammonia, N.D IOO = 5 amperes and 
 5 volts. Time 10 minutes. 
 
 Copper present 0.2742 gram, antimony 0.2500 gram. 
 
 This experiment resulted in the precipitation of nearly 
 all of the antimony with the copper. 
 
 3. FROM ARSENIC. 
 
 (a) In ammoniacal solution. Dilution 125 cc., 25 cc. of 
 ammonia, 2.5 grams of ammonium nitrate, N.D IOO = 5 
 amperes and 7 volts. Time 15 minutes. 
 
 Copper present 0.2742 gram, arsenic o. 2 500 gram. Cop- 
 per found 0.2740 gram-o.274i gram-o.274i gram. 
 The deposit was dark in color, smooth and adherent. 
 
 (b) In nitric acid solution. The conditions were the 
 same as were used in the separation of copper from 
 aluminium. 
 
 Copper present 0.2742 gram, arsenic o. 2 500 gram. Cop- 
 per found .2741 gram-.2742 gram-.2742 gram. 
 
 4. FROM CADMIUM. 
 
 (a) In nitric acid solution. The same conditions were 
 used as in the separation of copper from aluminium. 
 
 Copper present 0.2742 gram, cadmium 0.2500 gram. 
 Copper found 0.2742 gram-o.2742 gram-o.2742 gram. 
 
 5. FROM CHROMIUM. 
 
 (a) In sulphuric acid solution. The same conditions 
 were used as in the separation of copper from aluminium. 
 
 Copper present 0.2890 gram, chromium 0.2500 gram. 
 Copper found 0.2890 gram-o.289i gram-o.289o gram. 
 
Better deposits were obtained by starting the current 
 at 3 amperes and raising gradually to 5 amperes. 
 
 (6) In nitric acid solution. The same conditions were 
 used as in the separation of copper from aluminium. 
 
 Copper present 0.2874 gram, chromium 0.2500 gram. 
 Copper found 0.2874 gram-o.2875 gram-o.2874 gram. 
 
 If the current was allowed to run above 3 amperes the 
 deposit weighed too high. A blank was run with chro- 
 mium alone under the same conditions, which gave 0.0022 
 gram of a metal showing all the tests for chromium. 
 
 (c) In phosphoric acid solution. The same conditions 
 were used as in the separation of copper from aluminium. 
 
 Copper present 0.2742 gram, chromium 0.2500 gram. 
 Copper found 0.2742 gram-o.274o gram-o.2742 gram. 
 
 Slight traces of phosphorus were found in the deposits. 
 
 6. FROM COBALT. 
 
 (a) In nitric acid solution. The same conditions w^ere 
 observed as in the separation of copper from aluminium. 
 
 Copper present 0.2874 gram, cobalt 0.2500 gram. Cop- 
 per found 0.2875 gram-o.2874 gram-o.2874 gram. 
 
 Cobalt was partially deposited in sulphuric acid and 
 phosphoric acid electrolvte. 
 
 7. FROM IRON. 
 
 (a) In sulphuric acid solution. The same conditions 
 were used as in the separation of copper from aluminium. 
 
 Copper present 0.2696 gram, iron 0.2500 gram. Copper 
 found 0.2694 gram-o.2695 gram-o.2696 gram-o.2696 
 gram-o.2695 gram. 
 
 (6) In nitric acid solution. The same conditions were 
 observed as in the separation of copper from aluminium. 
 
 Copper present 0.2874 gram, iron 0.2500 gram. Copper 
 found 0.2873 gram-o.2875 gram-o.2874 gram. 
 
 (c) In phosphoric acid solution. The same conditions 
 were used as in the separation of copper from aluminium. 
 
8 
 
 Copper present 0.2742 gram, iron o.2Soc gram. Copper 
 found 0.2743 gram-o.274i gram-o.2742 gram, with 8 
 amperes in 5 minutes. Cu = 0.2741 gram. 
 
 Slight traces of phosphorus were found in these deposits. 
 
 8. FROM LEAD. 
 
 (a) In nitric acid solution. The results were low. Lead 
 seems to hold back the last traces of copper. 
 
 9. FROM MAGNESIUM. 
 
 (a) In sulphuric acid solution. The same conditions 
 were used as in the separation of copper from aluminium. 
 
 Copper present 0.2696 gram, magnesium 0.2500 gram. 
 Copper found 0.2696 gram-o.2696 gram-o.2695 gram. 
 
 (b) In nitric acid solution. The same conditions were 
 used as in the separation of copper and aluminium. 
 
 Copper present 0.2874 gram, magnesium 0.2500 gram. 
 Copper found 0.2874 gram-o.2874 gram-o.2875 gram. 
 
 If the current was allowed to run too high a white de- 
 posit was obtained which dissolved in sulphuric acid 
 without effervescence. A neutral solution of Mg. (NC>3)2 
 acidified with one drop of nitric acid and electrolyzed 
 with a current 2-3 amperes and 15 volts for 20 minutes 
 gave a white coating weighing 0.0334 gram. 
 
 (b) In phosphoric acid solution. The same conditions 
 were used as in the separation of copper from aluminium. 
 
 Copper present 0.2742 gram, magnesium 0.2500 gram.. 
 Copper found 0.2742 gram-o.274o gram-o.2742 gram. 
 
 10. FROM MANGANESE. 
 
 (a) In sulphuric acid solution. The same conditions 
 were used as in the separation of copper from aluminium. 
 
 Copper present 0.2890 gram, manganese 0.2500 gram. 
 Copper found 0.2890 gram-o.289i gram-o.289o gram. 
 
 (b) In nitric acid solution. The same conditions were 
 observed as in the separation of copper from aluminium. 
 
Copper present 0.2874 gram, manganese 0.2500 gram. 
 Copper found 0.2872 gram-o.2874 gram-o.2874 gram. 
 
 Only a part of the manganese was deposited as peroxide 
 on the anode, but no floating particles were observed in 
 the liquid. 
 
 11. FROM NICKEL. 
 
 (a) In sulphuric acid solution. No satisfactory deposits 
 were obtained. All conditions were tried. The nickel 
 seems to hold the copper back when they are present in 
 equal amounts. When the copper is greatly in excess it 
 carries the nickel down with it. 
 
 (b) In nitric acid solution. See the thesis of Exner.* 
 
 (c) In phosphoric acid solution. Nickel is partially 
 deposited in this electrolyte. 
 
 12. FROM URANIUM. 
 
 (a) In sulphuric acid solution. The same conditions 
 were used as in the separation of copper from aluminium. 
 
 Copper present 0.2890 gram, uranium 0.2500 gram. 
 Copper found 0.2889 gram-o.289o gram-o.289o gram. 
 
 (b) In nitric acid solution. The same conditions were 
 observed as in the separation of copper from aluminium. 
 
 Copper present 0.2742 gram, uranium 0.2500 gram. 
 Copper found 0.2742 gram-o.274i gram-o.2742 gram. 
 
 13. FROM ZINC. 
 
 (a) In sulphuric acid solution. Dilution 125 cc., i cc. 
 of sulphuric acid (Sp. G. 1.83), N.D IOO = 3-5 amperes and 
 5 volts. Time 10 minutes. 
 
 Copper present 0.2890 gram, zinc 0.2500 gram. Copper 
 found 0.2890 gram 0.2889 gram-o.2889 gram-o.289o 
 gram-o.2888 gram. 
 
 The current was raised gradually. The deposits were 
 excellent. 
 
 * Jour. Am. Ch. Soc., Vol. XXV, p. 896. 
 
JO 
 
 (b) In nitric acid solution. See the thesis of Exner.* 
 
 (c) In phosphoric acid solution The same conditions 
 were observed as in the separation of copper from alumin- 
 ium. 
 
 Copper present 0.2635 gram, zinc 0.2500 gram. Copper 
 found 0.2635 gram-o.2633 gram-o.2634 gram. 
 
 Slight traces of phosphorus were found in these deposits. 
 
 CADMIUM. 
 
 1. FROM ALUMINIUM. 
 
 (a) In sulphuric acid solution. Dilution 125 cc., i cc. 
 of sulphuric acid (Sp. G. 1.83), N.D IOO = 5 amperes and 
 5 volts. Time 10 minutes. 
 
 Cadmium present 0.2727 gram, aluminium 0.2500 gram. 
 Cadmium found 0.2728 gram-o.2727 gram-o.2727 gram. 
 
 The deposits were excellent, although slightly spongy, 
 but perfectly adherent. 
 
 (b) In phosphoric acid solution. Dilution 125 cc., 10 cc. 
 of phosphoric acid (Sp. G. 1.083), 50 cc. of a 10% solution 
 of Na2HPO4, N.D IOO = 5 amperes and 7 volts. Time 10 
 minutes. 
 
 Cadmium present 0.3032 gram, aluminium 0.2500 gram. 
 Cadmium found 0.3031 gram-o.3032 gram-o.3032 gram. 
 These deposits all showed slight traces of phosphorus. 
 
 2. FROM CHROMIUM. 
 
 (a) In sulphuric acid solution. A beautiful silver white 
 crystalline deposit of cadmium was obtained, which 
 always weighed low. 
 
 (b) In phosphoric acid solution. The same conditions 
 were observed as in the separation of cadmium from 
 aluminium. 
 
 Cadmium present 0.3600 gram, chromium 0.2500 gram. 
 Cadmium found 0.3603 gram-o.36oo gram-o.36oo gram. 
 
 * Jotir. Am. Ch. Soc., Vol. XXV, p. 896. 
 
II 
 
 3. FROM COBALT. 
 
 (a) In sulphuric acid solution. Cobalt is partially 
 precipitated in this electrolyte. 
 
 (b) In phosphoric acid solution. Cobalt is partially 
 precipitated in this electrolyte. 
 
 4. FROM IRON. 
 
 (a) In sulphuric acid solution. The same conditions 
 were used as in the separation of cadmium from alumin- 
 ium. 
 
 Cadmium present 0.3032 gram, iron 0.2500 gram. Cad- 
 mium found 0.3031 gram-o.3032 gram-o.3032 gram. 
 
 (b) In phosphoric acid solution. The same conditions 
 were used as in the separation of cadmium from alumin- 
 ium. 
 
 Cadmium present 0.3032 gram, iron 0.2500 gram. Cad- 
 mium found 0.3032 gram-o.3O3i gram-o.3032 gram. 
 
 5. FROM MAGNESIUM. 
 
 (a) In sulphuric acid solution. The same conditions 
 were observed as in the separation of cadmium from alu- 
 minium. 
 
 Cadmium present 0.2727 gram, magnesium 0.2500 gram. 
 Cadmium found 0.2727 gram-o.2728 gram-o.2727 gram. 
 
 (b) In phosphoric acid solution. The same conditions 
 were used as in the separation of cadmium from alumin- 
 ium. 
 
 Cadmium present 0.3600 gram, magnesium 0.2500 gram. 
 Cadmium found 0.3600 gram-o.3599 gram-o.36oo gram. 
 
 6. FROM MANGANESE. 
 
 (a) In sulphuric acid solution. The same conditions 
 were used as in the separation of cadmium from alumin- 
 ium. 
 
 Cadmium present 0.2727 gram, manganese 0.2500 gram. 
 Cadmium found 0.2725 gram-o.2727 gram-o.2727 gram. 
 
12 
 
 (b) In phosphoric acid solution. The same conditions 
 were used as in the separation of cadmium from alumin- 
 ium. 
 
 Cadmium present 0.3600 gram, manganese 0.2500 gram. 
 Cadmium found 0.3600 gram-o.36oi gram-o.36oo gram. 
 
 7. FROM NICKEL. 
 
 (a) In sulphuric acid solution. The same conditions 
 were used as in the separation of cadmium from alumin- 
 ium. 
 
 Cadmium present 0.2727 gram, nickel 0.2500 gram. 
 Cadmium found 0.2727 gram-o.2727 gram-o.2726 gram. 
 
 (b) In phosphoric acid solution. The nickel was partially 
 precipitated in this electrolyte. 
 
 8. FROM ZINC. 
 
 Zinc always came down with the cadmium in sulphuric 
 acid solution and also in phosphoric acid solution. 
 
 SILVER. 
 
 1. FROM ALUMINIUM. 
 
 In nitric acid solution. Dilution 125 cc., i cc. of nitric 
 acid (Sp. G. 1.43), N.D IOO = 3 amperes and 3.5 volts. 
 Time 15 minutes. 
 
 Silver present 0.2600 gram, aluminium 0.2500 gram. 
 Silver found 0.2600 gram-o.2599 gram-o.26oo gram. 
 
 The deposits obtained in this electrolyte were very poor. 
 The addition of ammonium nitrate helped matters but 
 little. Great care was necessary in washing not to lose 
 some of the deposit. 
 
 2. FROM CADMIUM. 
 
 (a) In nitric acid solution. Conditions same as No. i. 
 Silver present 0.2600 gram, cadmium 0.2500 gram. 
 Silver found 0.2600 gram-o.2598 gram-o.26oi gram. 
 
13 
 
 3. FROM CHROMIUM. 
 
 (a) In nitric acid solution. Conditions same as No. i. 
 Silver present 0.2600 gram, chromium 0.2500 gram. 
 Silver found 0.2601 gram-o.2598 gram-o.26oo gram. 
 
 4. FROM COBALT. 
 
 (a) In nitric acid solution. Conditions same as No. i. 
 Silver present 0.2600 gram, cobalt 0.2500 gram. 
 Silver found 0.2600 gram-o.2598 gram-o.26oo gram. 
 
 5. FROM IRON. 
 
 (a) In nitric acid solution. Conditions same as No. i . 
 Silver present 0.2600 gram, iron 0.2500 gram. Silver 
 found 0.2599 gram-o.26oo gram-o.26oo gram. 
 
 6. FROM LEAD. 
 
 (a) In nitric acid solution. Conditions same as No. i. 
 Silver present 0.2600 gram, lead 0.2500 gram. Silver 
 found 0.2596 gram-o.26oi gram-o.26oo gram. 
 
 7. FROM MAGNESIUM. 
 
 (a) In nitric acid solution. Conditions same as No. i . 
 Silver present 0.2600 gram, magnesium 0.2500 gram. 
 Silver found 0.2599 gram-o.26oo gram-o.26oo gram. 
 
 8. FROM MANGANESE. 
 
 (a) In nitric acid solution. Conditions same as No. i . 
 Silver present 0.2600 gram, manganese 0.2500 gram. 
 Silver found 0.2600 gram-o.26oo gram-o.2599 gram. 
 
 9. FROM NICKEL. 
 
 (a) In nitric acid solution. Conditions same as No. i. 
 Silver present 0.2600 gram, nickel 0.2500 gram. Silver 
 found 0.2599 gram-o.2599 gram-o.26oo gram. 
 
10. FROM ZINC. 
 
 (a) In nitric acid solution. Conditions same as No. i . 
 
 Silver present 0.2600 gram, zinc 0.2500 gram. Silver 
 found 0.2601 gram-o.2598 gram-o.26oo gram. 
 
 Silver was also tried in potassium cyanide solution 
 but owing to the great number of metals deposited from 
 this electrolyte and the high current density used with 
 the rotating anode no success was attained. 
 
 MERCURY. 
 
 While mercury itself is easily determined by the rotating 
 anode, it is almost impossible to make any separations of 
 it from other metals, owing to the readiness with which 
 the metal forms amalgams. 
 
 Aluminium and magnesium were the only successful 
 separations. From both of these metals the mercury was 
 deposited in beautiful mirror-like form. 
 
 Iron, chromium, nickel, cobalt, zinc, manganese and 
 cadmium were tried in both sulphuric and nitric acid 
 solutions without success. 
 
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