HYDROCHLOEIC ACID. 



89 



because its action on plants is deadly. Bolley, in 1894, tried to use 

 the antici-yptogamic properties of hydrochloric acid against potato 

 scab. The germs of this disease are killed, it is true, by steeping 

 from five to twenty-four hours in a 2 per cent solution of this acid, but 

 the eyes of the potato suffer so badly that this method cannot be 

 advantageously used. Wuthrich, in a research published in 1892 on 

 the action of metallic salts and acids on the spores of different fungi, 

 proved that the amount of this acid required to prevent the germina- 

 tion of spores compared with that of sulphuric acid used is proportional 

 to their chemical equivalents. Thus a solution of 0'0036 of HCl has 

 the same anticryptogamic effect as a solution of 0'0049 per cent of 

 H2SO4. A solution of HCl of 0"0036 per cent of sulphuric acid pre- 

 vents germination of the conidia and zoospores of Phytophthora in- 

 festans, De By. ; the conidia and the zoospores of Peronospora 

 viticola, De By. ; the spores of Ustilago carbo, Tul. But to prevent the 

 germination of the uredospores of Puccinia graminis, Pers., acid of 

 0"036 per cent is required. Hydrochloric acid can replace sulphuric 

 acid wherever the latter has given good results, if the plant be not 

 unfortunately as sensitive as the spores of fungi. 



Action of Chlorine and Hydrochloric Acid on Plants. — Hydro- 

 chloric acid and bleaching- powder factories discharge chlorine and 

 hydrochloric acid vapours into the air. The injurious effect of this 

 gas makes itself felt sometimes two miles from the factory, a radius 

 within which it kill plants. This gas is even more poisonous than 

 sulphurous acid itself ; deciduous trees suffer as well as evergreens. 

 The pathological condition ot the plant attacked is distinguished by 

 the brown border which forms on the leaves; then they are covered 

 with brown spots. The needles of spruce fir trees become yellow at 

 the point, dry up, and drop off. The analysis of the dry substance of 

 the diseased plant twenty-five minutes distant from these factories, 

 according to Konig, Steffeck, and Heine, gave the following results : — 



TABLE XV. — Shoxcing the Effect on the Chlorine Content of Forest Timber of 

 Proximity to a Hydrochloric Acid Works. 



These analyses show that the disease is produced by the absorption of 

 chlorine and hydrochloric acid. 



