456 Mr. Smith on the Hydrates of Nitric Acid. 



gas-holder, and turning the stop-cock at the top, which was 

 in connexion with the apparatus, a constant flow of perfectly 

 dry air was caused to bubble through the nitric acid in the 

 retort, the level of which was kept 2 or 3 inches above the 

 orifice of the tube in the interior, the only passage for the air 

 being through the long desiccating tubes. Aspiration kept 

 up for two or three hours was found to be generally sufficient 

 to decolorize completely 6 or 7 ounces of nitric acid. 



The acid before decolorization had a specific gravity of 

 1*522, and after the process fell to 1*503. Fifty grs. of the 

 colourless nitric acid were accurately weighed out in a stoppered 

 specific gravity bottle, to which was cautiously added, whilst 

 in the bottle, with a view to prevent any loss from splashing, 

 a known weight of perfectly pure carbonate of soda, recently 

 ignited in a porcelain crucible, until the solution was perfectly 

 neutral to test-paper. The absence of any sulphate or chlo- 

 ride in the carbonate had been previously ascertained. 



I. Carbonate of soda required 40*23 grs. 



II. Carbonate of soda required 40*23 grs. 



The quantity of carbonate of soda that 50 grs. of acid re- 

 quired for saturation, then, was 40*23 grs., which corresponds 

 to 40*78 grs. of nitric acid, or 81*56 per cent. 



An acid containing 1^ equiv. of water would contain in 

 100 parts — 



Real nitric acid .... 80 

 Water 20 



Too 



A portion of the prepared acid, amounting to about 5 

 ounces, was introduced into a small retort, through the tubu- 

 lure of which was fitted tightly, by means of a stopping of 

 moist clay, a delicate thermometer, which was kept immersed 

 in the liquid. The acid began to boil at 190", and before the 

 distillation had come to an end it had risen to 250°. The 

 acid coming over between 190° and 200° was collected apart 

 to be examined by saturation. 



50 grs. of the acid which remained in the retort boiling at 

 250° were then examined, and found to require 31*20 grs. of 

 carbonate of soda in the first experiment, and 31*07 in the 

 second, for saturation ; the mean of the two experiments would 

 correspond to 63*11 per cent, of nitric acid. 



50 grs. of the most volatile portion, namely, that which 

 came over between the temperatures of 190° and 200°, were 

 then weighed out exactly ; this quantity was found to require 

 no less than 41*92 grs. in the first experiment, and 41*91 in 

 the second, corresponding to 84*96 per cent, nitric acid ; but 

 then it must be remembered that this acid had a very dark 

 red colour. 



