EXISTENCE OF AMMONIA IN RAIN. 91 



Experiments made in this laboratory (Giessen) 

 with the greatest care and exactness have placed the 

 presence of ammonia in rain-water beyond all doubt. 

 It has hitherto escaped observation, because no per- 

 son thought of searching for it.* All the rain-water 

 employed in this inquiry was collected 600 paces 

 southwest of Giessen, whilst the wind was blowing 

 in the direction of the town. When several hundred 

 pounds 'of it were distilled in a copper still, and the 

 first two or three pounds evaporated with the addi- 

 tion of a little muriatic acid, a very distinct crystal- 

 lization of sal-ammoniac was obtained : the crystals 

 had always a brown or yellow color. 



Ammonia may likewise be always detected in snow- 

 water. Crystals of sal-ammoniac were obtained by 

 evaporating in a vessel with muriatic acid several 

 pounds of snow, which were gathered from the sur- 

 face of the ground in Marcl% when the snow had a 

 depth of 10 inches. Ammonia was set free from 

 these crystals by the addition of hydrate of lime. 

 The inferior layers of snow which rested upon the 

 ground contained a quantity decidedly greater than 

 those which formed the surface.f 



It is w^orthy of observation, that the ammonia con- 

 tained in rain and snow water possesses an offensive 

 smell of perspiration and animal excrements, — a 

 fact which leaves no doubt respecting its origin. 



not be too distinctly kept in mind that humic acid is the product of the 

 decomposition of Az^mM5, by means of caustic alkalies. Again, if the 

 colored solutions of humates of ammonia, lime, or magnesia, be poured 

 upon good mould or decayed oak-wood (which is nearly pure humus), 

 and allowed to filter, the solutions are observed to pass through quite 

 colorless ; they are decolorized just as if they had been filtered through 

 charcoal. Here, then, humus possesses the property of extracting hu' 

 mic acid from water ; or, in other words, soils have the power of ren- 

 dering humic acid insoluble, or unfit for assimilation. — Ep, 



* It has been discovered by Mr. Hayes in rain- water in Vermont, 

 — and in hailstones by M. Girardin, see London and Edinburgh Philo- 

 sophical Magazine, 1839, Vol. XV. p. 252. See note in Appendix. 



t Johnston detected it in snow which fell at Durham, G. B., by add- 

 ing two drops of sulphuric acid to four pints of snow-water, evaporating 

 to dryness, and mixing the dry mass with quicklime or caustic potash. 

 The residual mass contained a brown organic matter, mixed with the 

 sulphate of ammonia. 



