NITRIC ACID. 



31 



atmosphere, below 3000 metres, and that above that height no 

 nitrates are found in rain or snow. 



The amount of nitric acid in air is so small that it can only 

 be detected, as a rule, by examination of rain-water, in which 

 it becomes more concentrated. 



Bain-water, too, brings down ammonia and suspended 

 matter, so that analyses of rain-water are valuable as indi- 

 cations of the composition of the atmosphere. Many such 

 analyses have been published. Thus Angus Smith* in 1872 

 gave the following as the result of a large number of 

 analyses : 



ANALYSES OF BAIN-WATER. 

 PARTS PER MILLION. 



In these analyses it is to be noted that the chlorine is 



Jour. Chem. Soc. 1872, 33. 



