Io6 POISONS : THEIR EFFECTS AND DETECTION. [§§ 79, 80. 
The present law on the subject is, that the maximum quantity of acid 
escaping shall not exceed 2 grains per cubic foot of the air, smoke, or 
chimney gases ; and, according to the reports of the alkali inspectors, the 
condensation by the improved appliances is well within the Act, and 
about as perfect as can be devised. 
It appears from the reports of the Belgian Commission in 1855, when 
virtually no precautions were taken, that the gases are liable to injure 
vegetation to the extent of 2000 metres (2187 yards) around any active 
works ; the more watery vapour the air contains, the quicker is the gas 
precipitated and carried to the earth. If the action of the vapour is 
considerable, the leaves of plants dry and wither ; the chlorophyll be¬ 
comes modified, and no longer gives the normal spectrum, while a 
thickening of the rind of trees has also been noticed. The cereals suffer 
much ; they increase in stalk, but produce little grain. The legumi- 
nosse become spotted, and have an air of dryness and want of vigour ; 
while the potato, among plants utilised for food, appears to have the 
strongest resistance. Vines are very sensitive to the gas. Among trees, 
the alder seems most sensitive ; then come fruit-trees, and last, the 
hardy forest-trees—the poplar, the ash, the lime, the elm, the maple, 
the birch, and the oak. 1 
§ 79. Action upon Cloth and Manufactured Articles.— On black 
cloth the acid produces a green stain, which is not moist and shows no 
corrosion. On most matters the stain is more or less reddish ; after a 
little time no free acid may be detected by simply moistening the spot ; 
but if the stain is cut out and boiled with water, there may be some 
evidence of free acid. The absence of moisture and corrosion distin¬ 
guishes the stain from that produced by sulphuric acid. 
§ 80. Poisonous Effects of Hydrochloric Acid Gas.— Eulenberg 2 has 
studied the effects of the vapour of this acid on rabbits and pigeons. 
One of these experiments may be cited in detail. Hydrochloric acid gas, 
prepared by heating together common salt and sulphuric acid, was passed 
into a glass shade supported on a plate, and a rabbit was placed in the 
transparent chamber thus formed. On the entrance of the vapour, there 
was immediate blinking of the eyes, rubbing of the paws against the 
nostrils, and emission of white fumes with the expired breath, while the 
respiration was irregular (40 to the minute). After the lapse of ten 
minutes, the gas was again introduced, until the atmosphere was quite 
1 Those who desire to study more closely the effect of acids generally on vegeta¬ 
tion may consult the various papers of the alkali inspectors contained in the Local 
Government Reports. See also Schubarth, Die saueren Gase, welche Schwefelsdure 
und Soda-Fabrilcen verbreiten. Verhandlungen des Vereins zur Beforderung des 
Gewerbejieisses in Preussen, 1857, S. 135. Dingier's Journal, cxlv. 374-427. 
Christel, “ Ueber die Einwirkung von Sauren-Dampfen auf die Vegetation,” 
Arch. f. Pharmacie, 1871, p. 252. 
Vierteljahrsschrift fur gerichtliche Medicin, xvii. 404, 1872. 
2 Gewerbe Hygiene, Berlin, 1876, S. 15. 
