A Dye Extremely Sensitive to Copper E. I. STEARNS, Research Department, Calco Chemical Division, American Cyanamid Company, Bound Brook, N. J.
D
URIKG spectrophotometric measurements of dyestuffs the sensitivity of Benzo Fast Yellow 5GL to the presence of copper was found to be 40 times as great as the carbamate method of test. While not necessarily proposed as an analytical method, it was thought that this sensitivity would be of interest. Figure 1 compares the curve shapes of a solution of Benzo Fast Yellow 5GL (C. I. 346, diphenylurea-p,p'-disazo-bissalicylic acid) at pH 9.0, temperature 23" C., and concentration of 30 mg. per liter with and without 0.1 mg. per liter of cupric ion added. Both solutions are stable over a 24-hour period. Analysis of the curve shows that the extinction coefficient of the pure dye and the metallized complex is the same a t 397 millimicrons, while the extinction coefficient has increased about 150 per cent a t 487 millimicrons (from 2.9 X lo3 to 7.4 X lo3 sq. cm. per gram). Using magnifying cams, it is possible to get a sensitivity of 0.5 per cent extinction coefficient, which means that a small fraction of this amount of copper can be detected. I n order to determine the sensitivity to a small amount of copper, the data shown in Figure 2 were obtained. Figure 2 shows the curves obtained using a magnifying cam with and without 10+ gram per liter of copper divalent ion present in a Benzo Fast Yellow 5GL solution. Since the linear distance
FIGURE2. EFFECTOF ADDED COPPER ON BENZO FASTYELLOW 5GL Magnifying cams A . 30 mf. er liter of dye in water at pH 9.0, 27 measured in 5-om. cell B . Same as A but with 0.001 mg. per liter of Cu + + added
2,
I
separating the two curves is readily divisible into tenkparts, it is evident that lo-' gram of copper per liter can be detected. The colorimetric reaction with sodium diethyldithiocarbamate and copper as measured on the spectrophotometer gives a test in which 4 X gram of copper per liter can be determined in a similar cell. Hence, on the basis of spectrophotometric measurement the Benzo Fast Yellow 5GL is about 40 times as sensitive as the sodium diethyldithiocarbamate. The carbamate test is ordinarily considered to have a sensitivity based on visual colorimetry with a Lovibond colorimeter of about low6gram, which closely approaches the spectrophotometric sensitivity. Visually the Yellow 5GL sensitivity would not so nearly approach the spectrophotometric sensitivity because a change of color, from a yellow to a redder yellow, is not so noticeable as the appearance of a color which is the case in the carbamate method. Hence, for visual work,
-
-
.o 210
azo
*SO
OCTAVAL (C,R,U) ' 332
a10
LOO
*so
..O
1(b94-6SS
FIGURE1. EFFECTOF ADDED COPPERON BENZOFAST YELLOW 5GL Normal cams A . 30 mg. per liter of dye in water at pH 9.0, 23' C., measured in 1-om. cell B . Same as A but with 0.1 mg. per liter of Cu + added +
568
July 15, 1942
ANALYTICAL EDITION
the sensitivity of the two methods of test would perhaps be equal. The Yellow 5GL is also reactive to iron, chromium, and nickel, but to a smaller extent, detecting only about 5 X 10+ gram per liter of iron. It has been useful as a measure of the general purity of distilled water as regards presence of metallic ions, but no method has been worked out to make it a specific test for copper. No effort has been made to determine the optimum conditions or to determine whether other closely related dyes are better. Direct Green B, which is also sensitive to copper, has been proposed (S), and has been found to have about the same sensitivity as the carbamate test spectrophotometrically. Hence the Yellow 5GL is also 40 t,imes as sensitive as Direct Green B, based on spectrophotometric measurements. The use of octaval (logarithm of wave length) for the abscissa of spectrophotometric curves (%’) is somewhat unusual but is particularly convenient when magnifying cams are used as in Figure 2. Thus the visual range (375 to 750 mu) is di-
569
vided into 100 logarithmic units and covers the range 200 to 300 c. r. u. This plotting range was used for the data of Figure 1. One fifth of this range, from 230 to 250 c. r. u., was magnified to full width and was the plotting range used for the data of Figure 2. For convenience in range-shifting and magnification changing, as is necessary in problems of this type, the use of a decimal system has been found most convenient. The X 5 ordinate magnification need not be so flexible in the case of solutions, since their concentration can be changed to cause them to fall within the plotted range. Hence it is necessary to have the x 5 log log 1/T scale only in the plotting range 10 to 50 per cent transmission. This is the ordinate used in Figure 2. The desirability of the log log 1/T scale is generally recognized (1).
Literature Cited (1) Muller, R. H.,IND.ENQ.CHEM.,ANAL.ED.,13, 684 (1941). (2) Shurcliff, W.A., J. Optical Soc. Am., 32, 229 (1942). (3) Sisley, W.P., and David, M., Bull. SOC. chim., IV, 47, 1188-92 (1930).
Effect of Container on Soluble Silica Content of Water Samples C. A. NOLL AND J. J. MAGUIRE, W. H. & L. D. Betz, Gillingham and Worth Sts., Philadelphia, Penna.
I
N POWER plant operation, particularly with modern highenough glass in a month to cause any detectable change in pressure boilers, the silica content of the raw water, feed the ordinary mineral analysis and that no significant change water, boiler water, and steam has become of prime imporwill be caused in 6 months. They were primarily concerned tance. with the effect of storage on natural or raw water and on The silica content of a boiler water sample is of importance distilled water samples, although they also tested dilute in limiting silica in the concentrated boiler water to a tolerable sodium carbonate solutions. value, so as to prevent scale formation. Particularly a t higher Data on resistance to chemical attack for four brands of boiler messures. careful control of the silica content of the chemical glassware have recently been presented (7). boiler water and steam may be required for the limitation of siliceous turbine blade deposits. Silica plays an important role in the intercrysTABLE I. CH.4NGES IN SILIC.4 CONTEST talline corrosion of boiler metal, and in evaluatTemperaing the effect of this constituent under varying ture at Which Silica as Si02 conditions it is important that the silica values Sample Original obtained reflect the true conditions existing in Container Added sample 3rd day 5th day 7th day 14th day O C . P , p . m . P.p.m. P . p . m . P , p . m . P.p.m. the water sample. Recently, methods have been developed for Sample Typical of Raw or Feed Water the controlled removal of silica from raw and Ordinary soda glass bottle 23 2. 95 2.0 boiler feed waters, and in the formulation of Pyrex bottle 23 2.0 95 2.0 2.2 accurate recommendations for such silica reHard-rubber bottle 23 2.0 2.0 moval i t is necessary that the water analyses 95 2.0 Resin-lined can 23 2.0 on which these recommendations are based be entirely representative of the silica content of Sample Typical of Boiler Water the water. For the proper routine control of Ordinary soda glass bottle 23 32.4 silica removal processes, it is obvious that the 95 32.4 Pyrex bottle 23 32.4 samples analyzed must be representative. 95 32.4 Hard-rubber bottle 23 32.4 A recent article by Belyea and Moody covers 95 32.4 in detail the sampling of steam and boiler Resin-lined can 23 32.4 water (9). This paper is concerned entirely Sample Typical of Condensate with the storage of water samples after collection. 0.4 0.6 0.9 Ordinary soda glass bottle 23 0.2 0.3 For the accurate determination of silica, glass 0.5 0.8 1.0 0.2 95 0.4 containers should not be employed (1). Collins 0.4 0.5 0.2 23 0.3 0.3 Pyrex bottle 0.5 0.4 95 0.4 0.6 0 . 2 and Riffinburg (9) pointed out the large increase 0.2 0.2 0.2 0.2 23 0.2 Hard-rubber bottle 0.2 0.2 0.2 0.2 0.2 95 in silica that will occur in poor glass bottles over 0.2 0.2 0.2 0.2 0.2 23 Resin-lined can a period of 8 months; they concluded that sam0.2 0.2 0.2 0.2 0.2 95 ples of water in good bottles will not dissolve I
