SULPHUROUS ACID. 81 



grubs, and that even a 20 per cent solution does not kill those of the 

 cochiilis. 



Phylloxera vastatrix (vine phylloxera). — The phylloxera dies if ex- 

 posed for twenty-four hours in an atmosphere containing 1 per cent of 

 SO^. Hence it was thought the injection of SOo in the soil would 

 destroy this injurious insect. Aman Vigie recommended injections 

 into the soil of a mixture of sulphur and sulphur fumes from the 

 beginning of the phylloxera invasion. Henneguy remarked that when 

 this treatment was applied in summer the spread of the disease was 

 circumscribed, and although this process may be insufficient to free 

 the vine entirely from its parasite, it destroys it to such an extent as 

 even to allow the vine to thrive. Mouillefert examined the effect of 

 SO^, both as gas and in solution, as well as its different salts. He 

 found that sulphites are quite powerless against the phylloxera. As 

 to gaseous SO., it has no action on insects near the surface of the soil 

 because this gas, with a great affinity for water, can never penetrate 

 deep enough into the soil. 



Mus amphibius, L. (Eat). — M. A. ter Mer advises the use of SO^ 

 to kill rats. Eags are dipped in molten sulphur and petroleum, these 

 are inserted into the burrows and lit. It requires about 4^ lb. of 

 sulphur per burrow. Taschenberg dissents ; he found that this method 

 failed, even if the gas is driven far into the burrows by means of 

 special bellows. 



Use of SOo in Closed Spaces. — The action of SOo is deadly to 

 insects when the air is saturated with it. It is used especially in 

 granaries against the Coleoptera and Lepidoptera injurious to the 

 stored grain. It has also been used on small trees which can be 

 covered with a tent or a cloche. The last method is used especially 

 to combat the cochylis of the vine. 



Mycogone perniciosa (mole disease of the mushroom bed), Psalliota 

 campestris, L. — Constantin and Dufour found that the spores of the 

 Mycogone are killed by prolonged contact with SO.3. Mushrooms are 

 in no way injured in an atmosphere containing this gas, even if the 

 fumigation lasts twenty-four hours. 



Hops. — The preservation of stored hops is not always an easy 

 matter. Disinfection with SO., does not always give the result ex- 

 pected. Behrens found that if SOo be incapable of killing the germs 

 of the parasite which infest hops, it has a good effect on their quality, 

 which it alters for the better. But it is chiefly against the invasion 

 of Coleoptera into granaries and on the vine that SO.2 does good work. 

 Amongst these insects are : — 



Calandra granaria (or wheat -weevil). — As a curative method 

 fumigation with S0._, is used. The doors and windows of the granary 

 are closed ; sulphur is then ignited in a vessel placed on a support 

 above a sheet of iron; 1500 grammes (3-3 lb.) of sulphur with 100 

 grammes (-22 lb.) of saltpetre, suffice to disinfect a space of 50 cubic 

 metres. The granary is left closed for twenty-four hours, then it is 

 cleansed with a 2 per cent solution of corrosive sublimate. The same 

 process is used to destroy Microlepidoptera, the grubs of which ravage 

 grain and flour granaries. 



6 



