30 Mr. V. H. Veley. The Conditions of the [June 2, 



gram of nitrogen peroxide. Attempts to prepare an acid of greater 

 concentration and more free from the peroxide proved unsuccessful. 



In the following table are given the amount of nitric acid in 1 c.c. 

 of each of the several samples. 



Amount of nitric acid 

 Sample. in 1 c.c. 



I 1-350 grams 



II 1-1890 



III ...... 1-0763 



IV 0-5183 



V . 0-2563 



Specific gravity 10/10. 



1-541 



1-512 



1-420 



not determined 



For each experiment 10 c.c. of the acid were placed in a small piece 

 of combustion tubing, which had previously been cleansed by being 

 filled with concentrated nitric acid and allowed to stand for several 

 hours, generally over night. The tubes were then rinsed several 

 times with water, and finally with water redistilled from potassium 

 permanganate. It was hoped that by this method all reducing sub- 

 stances might be completely destroyed. After introduction of the 

 acid the tubes were quickly sealed up and then heated to various 

 temperatures in water or paraffin baths. The experiments were con- 

 ducted in dull and generally foggy weather, advantageous at least 

 for them, as concentrated nitric acid is decomposed by direct sunlight. 

 At the end of each experiment the 10 c.c. of acid were poured into 

 100 c.c. of water, and the amount of nitrous acid determined by 

 the metaphenylenediamine method, as explained above ; this is then 

 reckoned in terms of nitrogen peroxide, the substance which imparts 

 the yellow tint to the impure acid. 



ance in this method of procedure, which both in his and my hands has proved more 

 successful than the air (or carbonic acid) current method, usually described in the 

 text books, when acids of specific gravity greater than 1-5 are required perfectly 

 colourless. 



The distillation method, however, presents one of two alternate difficulties : on 

 the one hand, in each repetition of the distillation the proportion of nitrogen per- 

 oxide is decreased, on the other, that of the water is increased. 





