1550
JOURNAL OF CHEMICAL EDUCATION S E P T E ~ E1929 R,
TESTING A REAGENT AS A LABORATORY EXERCISE IN QUANTITATIVE ANALYSIS * W. D. COLLINS, U. S. GEOLOGICAL SURVEY, WASAINGTON, D. C.
In reports of chemical investigations that appear in the journals it is not unusual to find the quality of reagents used indicated by stating the maker's name without any account of work by the authors to establish the purity or strength of the reagents, even sometimes when the whole investigation depends on the quality of the reagents. This might be a reasonable procedure if the literature showed a long history of accurately determined agreement between the manufacturer's claims and the composition of reagents. Unfortunately, most of the published material' on the subject has been on the lack of agreement and the unreliability of the claims for purity of reagents. The articles noted may not represent present conditions, but so long as any uncertainty remains it is dangerous to use for serious work reagents that have not been tested by the user. One of the chief reasons for the unreliability of reagents in the past has been the anxiety of purchasers to buy at the lowest price and thus discourage manufacturers who might wish to put into their reagents the work necessary to insure uniformly high standards of purity. Any course in quantitative analysis might include a t least one exercise on the testing of some reagent for strength and purity. Samples of various grades can be obtained easily. The reagent to be tested should be selected with referenceto the student's experience, A teacher giving such an exercise could use it to obtain better knowledge of the grade of reagents purchased. The students should better appreciate the importance of tests of reagents. Both might be led to appreciate how absurdly low the prices of reagents are in view of the work involved in testing them, to say nothing of the pains that must be taken in manufacturing and purifying chemicals to make them approach reasonable standards of purity for reagents. Directions for testing reagents have been available for a long time in books like the U. S. Pharmacopeia and Murray's Standards and Tests for Reagent and C. P. Chemicals. Recently standards and tests for many reagents have been published2 by the Committee on Analytical Reagents of the American Chemical Society. Standards and directions for testing have been distributed by manufacturers of reagents. The directions are readily available. It is necessary only to select for test the reagents whose examination will best fit into any particular course. * Presented before the Division of Chemical Education at the 77th Meeting of the American Chemical Society, Columbus, Ohio, April 29 to May 3, 1929. 1 J. Am. C h a . Soc., 15, 501 (1893); 26, 1644 (1904); Ind. Eng. Chem., 9, 109 (1917); 11, 1140 (1919); 12, 800 (1920); 15, 529, 1281 (1923). ' Ind. Eng. Chem., 17, 756 (1925); 18, 636, 759 (1926); 19, 645, 1369 (1927); 20, 797 (1928); Anal. Ed., Ind. Eng. Chem., 1, 171 (July 15, 1929).
