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I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
N. I-., for helpful criticism and suggestions in the preparation of the manuscript for publication. LITERATURE CITED
(1) Clibbens, D . A,, and Geake, A . , J . TextileZnst., 19, T 7 7 (1928). (2) Coppick, S., P a p e r T r a d e J . , 117, KO.7, 25-9 (1943). (3) Doering, H., Papier-Fabr., 38, 80 (1940). (4) Experimenter, Silk J . R a y o n World, 17, 2 3 (1941); 18, 25, 209 (1941). ( 5 ) Farrow, F. D., and Neale, S. M.,Shirley Inst. Memoirs, 3, 67-82 (1924).
Vol. 16, No. 6
(6) Fickentscher, H., C‘elldosechem., 13, 5s (1932). (7) Kraeiner, E. O., IND.ENG.CHEM.,30, 1200 (1938). (8) M a r k , H., “High Polymers”, Vol. 2, p. 279, New York, Interscience Publishers, 1942. (9) &lease,R. T., J . Research .YatZ. Bur. Standards, 22, 371 (1939). (10) I b i d . , 27, 551-3 (1941). (11) Staudinger, H . , “Die hochmolekularen organischen Verbindungen”, Berlin, Julius Springer, 1932. (12) Staudinger, H., and Heuer, W., Ber., 63, 222 (1930). (13) Staudinger, H., and Nodeu, R.. Ibid., 63, 721 (1930). (14) Strauss, F. L., and Levy. R . M.,PaDer Trade J., 114, N o . 18, 33-7 (1942).
‘Colorimetric Determination of Nickel in Bronze HENRY SEAMAN, 1261 D a l y Ave., Bethlehem, Pa.
M
AKY bronzes contain up to 1% of nickel. For these relatively small amounts it would appear that a colorimetric method might be satisfactory for routine work. Feigl (2) found that lead dioxide oxidized nickel in alkaline solution to a valence higher than 2, and that addition of dimethylglyoxime to this solution gave a red coloration rather than a precipitate, This procedure was improved by Rollet ( 4 ) , who used bromine water instead of lead dioxide, and this method has found many applications ( I , 3, 6). This reaction has been applied to the determination of nickel in bronze using a filter photometer such as the Cenco photelometer tvith a cell 10 mm. thick, taking about 17 ml. of solution. PROCEDURE
After the tin is removed by filtration as metastannic acid and the copper and lead by electrolysis, the remaining solution is diluted to 150 ml. and mixed. One milliliter is transferred by pipet to a 100-ml. tall-form beaker, 25 ml. of distilled water are added, and the mixture is shaken after addition of one drop of saturated bromine water. Seven drops of an ammoniacal solution of dimethylglyoxime (10 grams of dimethylglyoxime ,dissolved in 650 ml. of ammonium hydroxide and diluted to 1 liter) are added and the mixture is again shaken well. The orange-red color develops in alkaline solution immediately on shaking. The solution is transferred to a photelometer cell and the absorption determined with the use of the Cenco dark blue filter or a Corning blue filter such as No. 556. The maximum absorption occurs a t 475 mM. The per cent nickel is obtained from the usual type of straight-line curve plotted on semilog paper. The calibration data for this curve can be obtained through the use of a solution of a C.P. nickel salt standardized gravimetrically, or preferably by removing an aliquot from the regular sample, obtaining the colorimetric value from this aliquot, and using the remainder for a gravimetric determination. With bronzes containing manganese, iron, or aluminum, 3 to 5 drops of a solution of ammonium citrate (25 grams of ammonium citrate dissolved in 30 ml. of water) are added before addition of bromine water. RESULTS AND DISCUSSION
Some typical single results obtained by this method are shown in Table I. In general, it is believed the results are satisfactory for the usual type of bronze. The use of ammonium citrate does not eliminate the interference of manganese and iron but reduces it considerably. The precision and accuracy of this method in the range indicated are 0.02 to 0.04% nickel. To obtain satisfactory results with this method it is necessary to standardize on a procedure and use it for all determinations. Among the factors which can affect the intensity of the color are time of standing, amount of bromine used, amount of ammonium citrate used, shaking, and temperature. The color intensity increases on standing, the increase being greatest during the first 20 minutes, and tends to level off after 2 hours. -4 typical increase during the first 20 minutes would be from 0.58 to 0.60% nickel. The use of more than one drop of bromine water and the use of ammonium citrate tend to lower the color intensity slightly-for example, standard 52a gave 0.75y0 nickel with 1
drop of bromine water, 0.74% with 2 drops, and 0.71% with 5 drops. An approximately equal reduction in values for nickel is obtained ~ q i t h3 to 5 drops of the ammonium citrate solution, so that 5 drops of bromine water and 5 drops of the ammonium citrate solution give values of 0.67 to 0.68% nickel for this sample. Low results will also be obtained by the use of too small a drop of bromine water, in which case some nickel will be precipitated.
Table 1. Nickel Determinations on Bureau of Standards Sampler Sample Nickel NO. Interfering Elements Gravimetric Colorimetric % 70 % 37C Fe,0.17 0.58 0.59 37C Fe 0.17 0.58 0.575 37B Fe:0.21 0.46 0.46= 37B Fe, 0.21 0.45 0.46“ 52 Fe, 0.12 0.13 0.13 52 Fe 0 12 0.13 0 . 13a 124 Fe:0:38 0.45 0.47 124 Fe,0.38 0.45 0.46’ 52s. Fe, 0.05: Mn, 0.02 0.73 0.75 62 Fe. 1.13: h h . 1.59: Al.1.13 0.64 0.70“ hlanganese bronze Fe, 2.2; Mn, 3.1; dl,3.8 0.00 0.10s a Using 3 drops of ammonium citrate solution, 25 g r a m per 20 ml. b Using 5 drops of ammonium citrate solution, 25 grams per 30 ml. 0 A commercial sample. _
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Some experiments indicate that fairly vigorous shaking is necessary to develop the maximum color intensity, although the values obtained were indecisive. Temperature has little effect on the color, except that a hot solution will give a precipitate rather than a color. Temperatures somewhat above or below room temperature gave substantially the same values. To reduce the interference of iron and manganese, ammonium citrate may be added. Under these conditions, these elements will give a yellow solution. A proper choice of wave length might serve to eliminate this interference. However, with a blue filter the interference due to iron was found to be about 0.02% nickel for 1% iron, and 0.03% nickel for 1% manganese with the use of 3 drops of an ammonium citrate solution containing 25 grams of the salt in 30 ml. of water. The dark green Corning filter No. 401 reduced the interference somewhat but gave a less satisfactory curve. Copper and zinc in the amounts usually present offer no interference. LITERATURE CITED
Diehl, Harvey, “Applications of Dioximes to Analytical Chemistry”, P. 35, Columbus, Ohio, G. Frederick Smith Chemical Go., 1940. Feigl, F., B e r . , 57, 758 (1924). Murray, W. M.,Jr., and Ashley, S. E. Q., IND.ENG.CHEM., ANAL.ED.,10, 1 (1938). Rollet, A. P., Compt. rend., 183, 212 (1926). Snell and Snell, “Colorimetric Methods of Analysis”, 1’01. I, p. 314, New York, D . Van Sostrand Co., 1936. ~
