Vol. II. 



PUBLISHED BY THE ALUMNI ASSOCIATION 

 OF THE COLLEGE OF PHARMACY OF THE CITY OF NEW YORK 

 New York, April, 1895. 



No. 4. 



A CRITICAL STUDY OF BETTENDORF'S TEST AND ITS MODIFICATIONS. 



By DR. CHAS. O. CURTMAN. 

 Chairman of Research Committee B. 



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A NUMBER of experiments have been 

 ** made for the purpose of ascertaining 

 the conditions most favorable to the result 

 of the test for arsenic by stannous chloride 

 (Bettendorf's test and its modifications). 

 The inquiry was directed to the follow- 

 ing points : 



1. The limit ol sensitiveness of the test 

 in its various modifications. 



2. The best proportion of reagent to 

 specimen. 



3. The influence of the use of metallic 

 tin together with the stannous chloride. 



4. The influence of the presence of 

 other substances in the specimen tested. 



I. LIMIT OF SENSITIVENESS. 



The following reagents were used : 



a. The solution directed for Betten- 

 dorf's test by the U. S. P., consisting of a 

 saturated solution of pure stannous chlo- 

 ride in pure concentrated hydrochloric 

 acid. The specific gravity of this solution 

 was = 1.467. 



b. Metallic tin, perfectly pure, in thin 

 cylinders, from which shavings of about 

 0.1 Gm. were taken as needed. 



c. Stannous chloride solution prepared 



according to the German "Arzneibueh" 

 by saturating a mixture of 5 parts of 

 crystals of stannous chloride and 1 part of 

 hydrochloric acid with dry hydrochloric 

 acid gas. The specific gravity was = 

 1. 912. 



All the materials used were previously 

 tested for absence of arsenic by Gutzeit's 

 test, so as to exclude any fallacies arising 

 from the introduction of even small traces 

 of arsenic by the reagent, which might 

 cumulate with those in the specimen. 



It is easy enough to procure pure me- 

 tallic tin, but impossible to obtain from 

 local dealers hydrochloric acid sufficiently 

 free from arsenic to stand Gutzeit's test 

 for one hour; so that I had to distill from 

 purified sulphuric acid and pure sodium 

 chlorid the hydrochloric acid required for 

 the preparation of the reagents. 



A number of specimens of arsenic solu- 

 tion were made, containing free trioxide. 

 sodium metarsenitt. and sodium arsenate 

 in such proportion that each set corres- 

 ponded exactly to an equ d amount of As. 



They were: Arsenic trioxide (As 2 3 = 

 197.68), of which 1.31062 Gm. contain 1 

 Gm. of As. 



* Report No. i of Research Committee B, of the Committee of Revision of the U. S. P., 1890. 



