86 



THE ALUMNI JOURNAL. 



Sodium metarseniie (Na As 2 = 129.82) 

 of which 1.7332 Gm. contain 1 Gm. of 

 As. 



Sodium arsenate, U.S. P. (Na 2 H As 4 

 + 7 H 2 = 311.46), of which 4,51834 

 Gm. contain 1 Gm. of As. 



The solutions used for experiments 

 contained from 0.5 Gm. to 0.01 Gm. of 

 As. 



Of these 1 Cc. was used for each trial 

 and the amount of reagent mixed with 

 this varied from 1 Cc. to 3 Cc, so as to 

 correspond with the limits prescribed in 

 the pharmacopoeial tests. When metallic 

 tin was added to the reagent 1 Cc. each 

 of the specimen and the stannous chloride 

 solution was used. In some cases of 

 doubt a ten-fold quantity (10.30 Cc. etc.) 

 was used to obtain sufficient material for 

 colorimetic comparison. 



A uniform application of heat was 

 effected, whenever needed, by imbedding 

 the series of test tubes under observation 

 to an equal depth into a sandbath, heated 

 to about 8o° C. 



Whenever comparisons of color became 

 necessary to decide whether a deeper 

 color had been produced than that of the 

 unaffected reagent (as was especially 

 necessary with the yellowish solution of 

 the German Pharmacopoeia, or whether 

 a greater or less intensity of color char- 

 acterized the reaction, narrow graduated 

 cylinders of 10 cubic centimetres capacity 

 were used in a dark box, with light re- 

 flected from beneath, or occasionally, for 

 still greater accuracy, a pair of Hehner's 

 colorimeter cylinders of 100 Cc. capacity, 

 also placed for observation into a dark 

 box, admitting from beneath light re- 

 flected upward by a plate of milk glass, 

 placed at an angle of 45 . 



With the aid of these appliances the 

 following results were obtained : 



a. With the U. S. P. solution of stan- 

 nous chloride, of specific gravity 1.467, 1 

 Cc. of each of the three specimens, con- 



taining 0.5 Mgm. of As was mixed in the 

 different proportions stated below, and 

 kept at ordinary temperature for one 

 hour. 



With 1 Cc of reagent a sharp reaction 

 had taken place at the end of the hour. 



With 2 Cc. of reagent the reaction was 

 obtained earlier and was more intense at 

 the end of one hour. 



With 3 Cc. of the reagent the reaction 

 was still more speedy and at the end of 

 the hour more intense. 



No difference could be noticed either 

 in time or intensity between arsenic in 

 the state of trioxid or pentoxid. 



When the test tubes were arranged ex- 

 actly as before, but placed in hot sand, 

 the time was somewhat shortened, and a 

 slight increase of intensity noticed in all 

 of the specimens. 



b. When 1 Cc of the U. S. P. solution 

 was used with 1 Cc of solutions contain- 

 ing 0.5 Mgm. of As and a small piece of 

 metallic tin added, and heat applied, the 

 reaction was almost instantaneous, and 

 in 3 minutes very sharp, unmistakable 

 coloration appeared, which continued to 

 increase in intensity for about 10 or 15 

 minutes, but was not notably darker at 

 the end of the hour. No difference ap- 

 peared in the different solutions contain- 

 ing arsenite or arsenate. 



c. When from 1 to 3 Cc. of the stannous 

 chloride solution of the German pharma- 

 copoeia was used with 1 Cc. of the solu- 

 tions containing 0.5 Mgm. of As, there 

 was a slight darkening of the color in a 

 few minules, which continued to increase 

 to the end of the hour, No difference 

 was perceivable between the arsenous and 

 the arsenic preparations. At 15 minutes, 

 the specimens treated by the U. S. P. so- 

 lution and metallic tin showed a much 

 greater intensity of color, but toward the 

 end of the hour there was but little dif- 

 ference perceptible between the color of 

 the specimens treated with 3 Cc of the 



