314 SULPHURETTED HYDROGEN. [BOOK n. 



this did not seem sufficient, and seven ounces of water were 

 found necessary to keep it in a condition similar to the other, 

 which was watered with three ounces, but under the influence of 

 the muriatic acid. It might at first be supposed that this effect 

 was principally due to the action of the carbonate of soda ; 

 but by comparing the plants with others similarly situated, 

 there appeared little doubt that the rate of evaporation was 

 diminished in that under the influence of the acid, and not 

 that it was increased in the one watered with the alkaline 

 solution/' 



Chlorine may be expected to have the effects of hydro- 

 chloric acid gas ; and so indeed it has, but they appear to be 

 developed more slowly. Two cubic inches, in two hundred 

 parts of air, did not begin to affect a mignonette plant for 

 three hours ; half a cubic inch, in a thousand parts of air, did 

 not injure another in twenty-four hours : but when the plants 

 did become affected, the same drooping, bleaching, and desic- 

 cation were observed. (Turner and Christison.) 



Nitrous acid gas is probably as deleterious as the sulphurous 

 and hydrochloric acid gases. In the proportion of a hundred 

 and eightieth, it attacked the leaves of a mignonette plant in 

 ten minutes; and half a cubic inch, in 700 volumes of air, 

 caused a yellowish green discoloration in an hour, and droop- 

 ing and withering in the course of twenty-four hours. The 

 leaves were not acid on the surface. (Turner and Christison.) 



The effects of sulphuretted hydrogen are quite different 

 from those of the acid gases. The latter attack the leaves at 

 the tips first, and gradually extend their operation towards 

 the leafstalks ; when in considerable proportion, their effects 

 began in a few minutes ; and if the quantity was not great, 

 the parts not attacked generally survived, if the plants were 

 removed into the air. The sulphuretted hydrogen acts dif- 

 ferently; two cubic inches, in 230 times their volume of air, 

 had no effect in twenty-four hours. Four inches and a half, 

 in eighty volumes of air, caused no injury in twelve hours ; 

 but, in twenty-four hours, several of the leaves, without being 



