INDUSTHIAL AND EKGIi$EERlXG CHEMISTRY
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FIGURE 4. SETTLING CHARACTERISTICS OF HYDROCARBON RESIN COMPARED WITH IODINE NUMBER 0
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FIGURE 3.
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DIOXIDEPIGMENT SPIRITS CONTAINIKG VARIOUSRESINS
SETTLINQ OF TITA~TIuM
IN
MINERAL
polarity of the carbon-to-carbon double bond, the settling of titanium dioxide in a nonpolar solvent containing a hydrocarbon resin may vary with the unsaturation of the resin. Hydrocarbon resins of varying degree of unsaturation were prepared from petroleum hydrocarbons by controlling the polymerizing conditions. Settling tests were made with each of the resins prepared, using a mixture of 3 grams of a 50 per cent resin solution in mineral spirits, 12 grams of mineral spirits, and 5 grams of pigment. The settling increased with increasing iodine number of the resin until an iodine number of approximately 180 was reached (Figure 4). A further increase in the iodine number beyond this point re-
sulted in a decrease in the rate of settling. This behavior may be due to the influence of a second factor-namely, molecular weight-which steadily decreases with increasing iodine number under the method of polymerization employed.
Literature Cited (1) Lowry, T. M.. J. Chem. SOC.,123, 822 (1923). (2) Polanyi, M., Umschau, 34, 1001 (1930). (3) Ryan, Harkins, and Gans, IND.ENQ.CEEM.,24, 1288 (1932). (4) Thomas, C. A., and Carmody, W. H., J. Am. Chem. Soc., 54, 2480-4 (1932); 55, 3854-6 (1933); IND. ENQ. CHEM.,24, 1125-8 (1932): U. S. Patents 1,836,629. 1,939,932 (1933): 1,947,626, 1,982,707, 1,982,708 (1934); 2,023,945, 2,039,363. 2,039,365,2,039,367 (1935) ; Canadian Patent 333,230 (June 13, 1933); British Patent 340,001 (March 12, 1931). ( 5 ) Thomas, C. A . , and Marling, P. E., ISD. ESQ. CHEM., 24, 871-3 (1932). RECEIVED September 15, 1936
(End of Symposium)
Improved Method for Electrodepositing Alloys H. KERSTEN
AND
WM.T. YOUNG
University of Cincinnati, Cincinnati, Ohio
W
HER the anode in an electroplating bath is an alloy, the metals of which it is composed do not usually dissolve in the correct proportion to produce a deposit with the same composition as the anode. I n some cases a deposit of the desired composition may be obtained by using an anode whose composition has been properly altered; in other cases frequent additions of salts of the metals which become depleted are made. In the improved method,' described here for nickel-iron alloys, the bath is kept saturated with respect to a salt of one of the metals (in this case, nickel formate), and the salt of the other (ferrous sulfate) is added continuously or a t frequent intervals. An insoluble anode is used, and the p H of the solution is kept constant by frequent additions of a neutralizing substance or by passing the electrolyte continuously over a solid 1
U.8.Patent
1,924,439 (1933).
neutralizing substance. With this method a number of alloys may be electrodeposited more conveniently and with a more uniform composition over a period of time, than with some of the older methods. The process is limited to those cases where one of the metals can be electrodeposited from a saturated solution, where the solutions do not react disadvantageously with each other chemically, and where a suitable neutralizing substance can be found. The apparatus is illustrated schematically in Figure 1: The electrolyte was contained in a one-liter beaker, immersed in a water bath whose temperature was held at 50" C. The electrolyte was siphoned from the bath t o a flask containing calcium carbonate which acted as a neutralizing agent. This agent was chosen because it is insoluble in water and therefore could not cause an excess of alkalinity, and because, as will be shown later,
ISDUSTRIAL -4ND ENGIKEERIXG CHEMISTRY
OCTOBER, 1936
the products which may be formed during the neutralization are eventually precipitated as calcium sulfate or as calcium f o r m a t e and removed from the solution. Cal-
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formly spilled into the plating bath. Agitation of the electrolyte was accomplished by oscillating the electrodes from side to side. A cathode could be withdrawn from the bath and another one immediately inserted without disturbing the other parts of the system. Stainless steel electrodes were used because an anode of such material is ractically insoluble and because the deposited alloy does not adfere well to the cat’hodeand can easily be peeled from it for chemical analysis.
Typical results are shown graphically in Figure 2. For curve A the iron was added a t the rate of 0.2 gram (as a feragent forevery platrous sulfate solution) per hour, and for curve B a t the rate of 0.3 gram of iron per hour. For curve A the current density ing bath. Probably in Some cases the . was held at 2 amperes per sq. dm. and for curve B a t 1.5. pH would have t o be kept const,ant by Curve c shows how quickly the composition of the deposit changed when no iron was added. I n Figure 3 curve A shows adding the neutralizing substance at the result of a n attempt to electrodeposit permalloy which intervals Or by the contains 21 per cent iron and 79 per cent nickel. For this ex.iiii> - 0 A \ -ii~:mov MorOR ~ ~ $ d f , , $ ~ periment ~ ~ ~the~ iron was added a t the rate of 0.26 gram (as a the iron. From the ferrous sulfate solution) per hour, and the current density was neutralizing flask held a t 1.5 amperes per sq. dm. The broken line near curve the liquid flowed -4 corresponds to the composition of permalloy and shows how through a filter containing calciumcarnearly the actual composition corresponded to that desired. bonate, which reCurve B illustrates how the composition of the electrolyte moved any suschanged during the experiment. I n the bath from which the PLTfRfD, LLZc-?wtTE Pended matter and permalloy was plated, the nickel-iron ratio was about 14.7 to ensured complete neutralization, 1; thesameratiointhedepositws~sabout 3.8 to 1. FIQTJRE 1. APPARATCSFOR ELECTRO- ~k~ so I n general, for nickel-iron alloys electrodeposited in this PLATINQ ALLOYS arranged t,hat it way, after the electrolysis and circulation have been carried be quickly on long enough for the electrolyte to reach a fixed composition, replaced by another when necessary. From this point the the Process probably continues as follows: the formic acid liquid entered a filter containing a large excess of nickel forformed by the electrolysis of the nickel formate combines mate so that it again became saturated with respect to the forwith the calcium carbonate to form calcium formate and carmate. The saturated liquid which under these conditions contained 24.5 grams per liter of nickel formate (7.8 grams per Mer of bon dioxide. The ferrous sulfate may combine with the talnickel), then entered a beaker from which it was pumped back cium formate to form ferrous formate and calcium sulfate so into the plating bath by an air pump at the rate of &bout750 cc, that the iron may be electrodeposited from both the ferrous per hour. The loss of liquid by evaporation was made up by adding a similarly saturated nickel formate solution t o the system at formate and a part of the ferrous sulfate which has not had the saturating funnel. time to combine. I n any case, the electrolyte is finally satuTo introduce the iron salt into the system, a glass plunger was rated with respect to nickel formate and calcium sulfate, and lowered at a constant rate into 1% tube containing a solution of ferit may also become saturated with calcium formate, dependrous sulfate, In this way the ferrous sulfate solution was uniing. on how much ferrous sulfate is being. added. The caicium sulfate is so slightly soluble that it is precipitated and caught in one of the filters. If more calcium formate than that needed to saturate the solution is produced, i t is also caught in one of the filters. Crystal structure photographs of the electrodeposit, made by the Hull-Debye-Scherrer method, showed that it had the same structure as t h a t of nickel; therefore the electrodeposited substance was not a mixture of iron and nickel crystals, but was probably I a solid solution of iron in nickel, as is the case when Ic i I
