FORMATION OB 1 NITRIC ACID. 219 



thunder-storms, contained more or less nitric acid, partly in com- 

 bination with lime, and partly with ammonia. In the sixty others, 

 only two contained traces of nitric acid. 



The occurrence of nitric acid in rain-water as nitrate of 

 ammonia, renders it uncertain whether the nitrogen of the former 

 was obtained from the atmospheric air itself, or from the ammonia 

 existing in it, in the state of a gas. Henry observed that ammo- 

 niacal gas, mixed with oxygen, and exposed to electric sparks, is 

 likewise converted into nitric acid. It is obvious, that, if the 

 rain contains carbonate of lime mechanically mixed with it in the 

 form of dust, the nitrate of ammonia also present will be con- 

 verted during evaporation into carbonate of ammonia, which will 

 escape, and into nitrate of lime, which remains in the residue. 

 The quantity of nitric acid contained in the rain of a thunder- 

 storm cannot be estimated. Two or three hundred pounds of 

 filtered rain-water yield only a few grains of a colored residue, 

 and the nitrates contained in the latter form only a fractional 

 part of its weight. 



The analysis of the water of springs and of rivers is much 

 better adapted to give us a clear conception of the quantity of 

 nitric acid formed by the influence of electricity in the atmo- 

 sphere. If we suppose the nitric acid to exist in water in a free 

 state, as it is a volatile acid, it must escape during the evapora- 

 tion of the water in porcelain vessels, so that the residue will not 

 contain a trace of it, if the bases necessary for its fixation be 

 deficient. The water of our springs, streams, and rivers, is rain- 

 water, which, if nitric acid were originally present in it, must 

 now contain nitrates, by filtering through the earth, which in- 

 variably contains lime and alkaline bases. 



It follows, from the interesting observations made by Gobel, in 

 his journey to Southern Russia, that, by the evaporation of the 

 river Charysacha, which falls into the lake Elton, the latter must 

 receive annually 47,777 millions of pounds of salts. The water 

 of the Charysacha contains scarcely 5 per cent, of salts ; so some 

 conception may be formed of the quantity of water which must 

 evaporate, in order to furnish the above quantity. The river has 

 its source about forty wersts from Lake Elton, and obtains its 

 water from the rain and snow falling on the mountains. 



