NITRIC ACID. 
§§ 8g, 90.] 
115 
§ 89. Action of Nitric Acid on Vegetation. —Nitric acid acts on 
plants injuriously in a twofold manner—viz., by direct corrosive action, 
and also by decomposing the chlorides which all plants contain, thus 
setting free chlorine, which decomposes and bleaches the chlorophyll. 
The action is most intense on soft and delicate leaves, such as those of 
clover, the cabbage, and all the cruciferge. The tobacco plant is particu¬ 
larly injured by nitric acid. Next to all herbaceous plants, trees, such 
as the apple, pear, and other fruit-trees, generally suffer. The coniferse, 
whether from their impregnation with resin or from some other cause, 
possess a considerable resisting power against nitric acid vapours, and 
. the same is true as regards the cereals ; in the latter case, their siliceous 
armour acts as a preserving agent. 
§ 90. Nitric Acid Vapour .—The action of nitric acid in a state of 
vapour, as evolved by warming potassic nitrate and sulphuric acid 
together, has been studied by Eulenberg. A rabbit was placed under a 
shade into which 63 grammes of nitric acid in a state of vapour were in¬ 
troduced. From the conditions of the experiment, some nitric peroxide 
must also have been present. Irritation of the external mucous mem¬ 
branes and embarrassment in breathing were observed. The animal in 
forty-five minutes was removed, and suffered afterwards from a croupous 
bronchitis, from which, however, it completely recovered in eleven days. 
A second experiment with the same animal was followed by death. On 
inspection, there was found strong injection of the cerebral membranes, 
with small extravasations of blood ; the lungs were excessively con¬ 
gested ; the right middle lobe especially was of a liver-brown colour, and 
empty of air : it sank in water. 
0. Lassar 1 has also made a series of researches on the influence of 
nitric acid vapour, from which he concludes that the acid is not absorbed 
by the blood, but acts only by its mechanical irritation, for he could not 
trace, by means of an examination of the urine, any evidence of such 
absorption. 
There are a few instances on record of the vapour having been fatal 
to men ; for example, the well-known case of Mr Haywood, a chemist of 
Sheffield, may be cited. In pouring a mixture of nitric and sulphuric 
acids from a carboy of sixty pounds capacity, the vessel broke, and for 
a few minutes he inhaled the mixed fumes. He died eleven hours after 
the accident, although for the first three hours there were scarcely any 
symptoms of an injurious effect having been produced. On inspec¬ 
tion, there was found intense congestion of the windpipe and bronchial 
tubes, with effusion of blood in the latter. The lining membrane of 
the heart and aorta was inflamed ; unfortunately, the larynx was not 
examined. 2 
1 Hoppe-Scylor’s Zeitschrift f. 'physiol. Chemie, Bd. i. 8. 165-173, 1877-78. 
2 Lancet, April 15, 1854, p. 430. 
