ATMOSPHERIC AIU AS THE FOOii Of PLANl'S. 79 



glass, porcelain, silver, etc.,) so that water would evapo- 

 rate rapidly from its surface. The purest water was then 

 dropped into the warm dish in small quantities at a time, 

 each portion being allowed to evaporate away before the 

 next was added. Over the vapor thus generated was held 

 the mouth of a cold bottle until a portion of the vapor 

 was condensed in the latter. 



The water thus ■^'oUccted gave the reactions for nitrous 

 acid and ammonia, sometimes quite intensely, again faint- 

 ly, and sometimes not at all. 



By simply exposing a piece of filter-paper for a suffi- 

 cient time to the vapors arising from pure water heated 

 to boiling, and pouring a few drops of acidified iodide-of- 

 potassium-ytarch-paste upon it, the reaction of nitrous acid 

 Avas obtained. When paper which had been impregnated 

 with dilute solution of pure potash was hung in the va- 

 pors that arose from water heated in an open dish to 100° 

 F., it shortly acquired so much nitrite of potash as to re- 

 act WMth the above named test. 



Lastly, nitrons acid and ammonia appeared when a 

 sheet of filter-paper, or a piece of linen cloth, which had 

 been moistened with the purest water, was allowed to dry 

 at ordinary temperatures, in the open air or in a closed 

 vessel. (Jour, fiir Prakt. Chem., Ixvi, 131.) These ex- 

 periments of Schonbein arc open to criticism, and do not 

 furnish perfectly satisfactory eviilence that nitrous acid 

 and ammonia are generated under the circumstances men- 

 tioned. Bohlig has objected that these bodies might be 

 gathered from the atmosphere, where they certainly exist, 

 though in extremely minute quantity. 



Zabelin, in the paper before referred to {Ann. Ch. Ph. 

 cxxx, p. 76), communicates some experimental results 

 which, in the writer's opinion, serve to clear up the mat- 

 ter satisfactorily. 



Zabelin ascertained in the first place that the atmos- 

 pheric air contained too little ammonia to influence Xess- 



