ANALYTICAL EDITION
April 15, 1942 10-
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with the concentration of the substance to be determined. As the concentration increases, there is likely to be more variation in the size and number of crystals with a consequent variation in the precision.
READlNG
.kClD BY FIGURE8. ESTIMATION OF ANTHRAQUINOKE-~,S-DISULFONIC ACETATE
?VlAXGASOTJs
Individual viilucs
3 XIean values.
to check the exactness with which the field could be found. The mean of nine readings n-as 27.7, and the standard deviation 0.80. When the mirror was reset but the slide was not moved after each observation, in order to test this operation, the average of nine readings was 27.7 and the standard deviation 0.35. X’ext, a series was run by shutting off the lamp but not disturbing anything else. Out of nine readings, it was found necessary to readjust the amperage to 4.6 four times. The average of nine readings was 26.5, and the standard deviation 0.35. These errors, which represent those encountered in the analysis of preformed particles, give a net standard deviation for a single reading of d O . 8 O 2 0.351~ 0.352,or 0.94 divi-
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sions. I n terms of anthraquinonebeta-sodium sulfonate this corresponds to 0.1 and 0.05 per cent, respectively, for the high and low concentration methods of analysis. In terms of anthraquinone-1,8-disulfonic acid by the barium method this corresponds to 3.5 per cent and by the manganese method to 0.1 per cent. The standard deviation for precipitated particles by the photoelectrometric method varies with the particular method in question, and
Acknowledgments The authors wish to thank IT.J. IIader for the preparation of the purified materials used in this work, G. L. Royer for assistance in developing the apparatus used, and E. I. Stearns for assistance with the statistical interpretations. Literature Cited E. M.,and Mason, C. JT., “Handbook of Chemical Microscopy”, 2nd ed., Vol. I. pp. 431-48, h’ew York, John Kiley & Sons, 1938. (2) Seaman, IT,, ISD. E A GCHEM., . . ~ X A L . ED., 11, 465-9 (1939).
(1) Chamot,
PRESENTBD before t h e Division of Analyticrtl and Micro Chemistry at t h e CHEMICAL SOCIETY,Atlantic City, N. J. 102nd Meeting of t h e AMERICAN
A Fuzz Detector for Viewing Glass Weighing Vessels in Organic Quantitative Microanalysis DOUGLASS F. HAY3IAN AND WILHELRI REISS Merck & C o . , Inc., Rahway, N. J.
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HE fuzz detector is a viewing light devised for detecting that the operator cannot see the light source but only the light coming over the surface of the tube. \Then the tubes are roforeign material on the surface of glass vessels. I t has tated slowly, any lint or foreign material on the glass surface been found very useful in the inspection of micro absorption appears sharply outlined against the black background of the tubes and other micro glassware for cleanliness prior to weighpainted portion of the lamp. The surface of the glass islightly ing. As shown in the accompanying figure, the detector constroked with chamois while still under observation and the sists of a standard %inch, 15-watt fluorescent lamp (white successful removal of lint and foreign material can be readily or daylight type) covered with several coats of black enamel, observed. Foreign material in the tip ends of absorption tubes except for two openings. The opening used for the viewing is easily removed by using a steel wire with a knurled end. of carbon and hydrogen absorption tubes is 5 inches long and The smaller opening is very useful for vierving glass vessels 0.25 inch wide and the other opening, used for shorter obsuch as weighing bottles, Rast molecular weight tubes, jects, is 1 inch long and 0.625 inch wide. A rotating tube chemical samples, etc. In the Rast molecular weight determade of heavy black paper placed around the lamp permits mination the tube can be either opening to be covcarefully checked for any ered while the other one foreign material before the is in use. first weighing and again For the detection of % in. i wide Ye in.wide after each addition of samfuzz on absorption tubes, ple and of camphor to enfilter tubes, eic., the tube sure that none of the maare held UD in front of the lamp aboit 0.5 inch from ,8 in, teridremains in the upper the narrow opening, so part of the tube.
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