THE PURITY OF THE FUSED ARGENTIC NITRATE. 



55 



THE PURITY OF THE FUSED ARGENTIC NITRATE. 



The first impurity for which search was made was air. While crystals 

 obtained from solution, although always containing solvent, may be sup- 

 posed to be free from air, the fused material can not without question 

 be assumed to be free from this impurity. The only manner of approach- 

 ing this question seems to be to fuse the salt a second time in a vacuum, 

 in order to detect a possible loss of weight. This Stas did in a single case, 

 with a negative result. Nevertheless, a single experiment, even of 

 Stas's, does not carry with it much weight; therefore the test deserves 

 repetition. 



This was carried out in the present case without great difficulty on 

 five of the preliminary determinations. The flasks containing the argen- 

 tic nitrate which had been fused for an hour in air were lowered into 

 mammoth test-tubes long tubes of soft glass 4.5 cm. in diameter 

 sealed at the lower end and scrupulously clean. A hood was placed over 

 the mouth of the flask to prevent fragments of glass from entering, and 

 the tube was drawn down in two large converging blast flames. A glass 

 tube was fused on and connected with an efficient mechanical hand 

 pump; several exhaustions, followed by admission of dry air, excluded 

 all moisture. Finally, the system was reduced to 2 mm. and sealed, and 

 heated to 210. After having been maintained in a state of fusion in the 

 dark for half an hour, the salt was cooled in the usual cautious fashion, 

 and air was admitted very slowly. The flask was placed in a desiccator 

 over night and weighed. The product was always slightly discolored, 

 indicating decomposition, but showed no serious loss in weight. 



* 



The Effect of Fusion in Vacuum. 



Forty-five grams of salt lost in all 0.00035 gram. This is less than 1 

 part in 100,000, and may safely be referred to the trace of decomposi- 

 tion indicated by the pale-brownish coloration. Not only is it reasonable 

 to suppose that but little air is dissolved (for according to the law of 

 Henry nearly all of it should have been expelled by this treatment) but 

 also one is led to infer that very little water remains to be expelled. This 



