CHEMICAL SCIENCE. 345 



entire plants, or in the neighborhood of extensive vegetation. Generally 

 the litmus paper has become discolored, but starched or ioduretted paper 

 only takes a Mac color under certain circumstances. Thus. with, manv of 



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the cactus family, the starched ioduretted paper does not become colored ; 

 it is sometimes colored by the action of light in the presence of the green 

 leaves of herbaceous plants, more rarely with the leaves of rose-trees, fre- 

 quently in contact with or in the neighborhood of moss, very rarely in an 

 inhabited locality. 



Not being able to draw any certain conclusions from these results, and as 

 the ozonomical paper is a very unfaithful re-agent, and liable to become 

 colored under the most various conditions, M. Luca tried some comparative 

 experiments upon the air surrounding a great many plants kept in a hot 

 house, and the free atmospheric air in a locality far removed from vegeta- 

 tion. For this purpose he arranged an apparatus in the hot-house of the 

 Botanic Garden at the Luxembourg. An aspirator caused the air to pass 

 slowly during the day, first into two glass tubes full of carded cotton, 

 then into sulphuric acid, then over potassium, and finally into dilute 

 solutions of pure potassa. The examination of the acid and alkaline 

 solutions after six months from April 1S5G, gave the following results: 

 The sulphuric acid contained ammonia, in considerable quantity; in 

 the alkaline solutions, to the number of three were found ; in the first, the 

 reactions of nitric acid, and some small crvstals of the nitrate, and in the 



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other two, the reactions of nitrates, but no crystals. 



A similar apparatus, arranged at the same time in the court of the labora- 

 tory of France, a place cut off from vegetation, gave the following results : 

 Ammonia was found as before in the sulphuric acid of the apparatus, which 

 undoubtedly proceeded from the atmosphere ; but it was impossible to find 

 the least trace of nitric acid in the alkaline solutions. 



These facts show that the alkaline solutions do not produce nitrites dur- 

 ing the day with a current of air containing ammonia, when this current is 

 fur away from vegetation, and that, on the contrary, the air of a hot-house, 

 in which are a great many plants of all kinds, produces nitrates with alka- 

 line solutions, even after passing through sulphuric acid, and thus deprived 

 of ammonia. Is this because plants act like porous bodies on the elements 

 of nitric acid contained in the atmosphere ? Direct experiments made far 

 f.-om vegetation with porous bodies of mineral origin prove the contrary, for 

 they do not produce nitrates. 



The experiments of Messrs. Andrews confirm the opinion that ozone, far 

 from being a pcr-oxide of hydrogen, is only modified oxygen, capable of 

 being estimated with the utmost precision. On the other hand, the phe- 

 nomena of oxidation which ozone .produces are not rare, and we know 

 how to take advantage for chemical analysis, of oxonizcd essence of 

 turpentine, of the ozone produced during the combustion of ether in contact 

 with platinum, etc. AVe know, likewise, that urea is formed in the animal 

 economy ; and M. Be champ has proved that this body may be produced 

 artificially by the oxidatioa of albuminoid substances, by means of hyper- 

 manganate of potash. 



