42 INSECTICIDES, FUNGICIDES, AND WEED KILLERS. 



Use. — Phylloxera. — To utilize this propert}% therefore, of hydrogen 

 sulphide, it only remains to discover a process capil)le of giving rise 

 to the formation of this gas in the layers of soil round an infected 

 vine. The alkaline sulphocarbonates fulfil this object. They decom- 

 pose in the presence of moisture and the acidity of the soil into alka- 

 line carbonate and hydrogen sulphide. 



K.CSa + H.,0 + CO, = K.fiO., + CS, + H.,S 



Potassium Water. Carbonic Potassium Carbon Hydrogen 



sulpho- acid. carbonate. disul- sulphide, 



carbonate. phide. 



Mouillefert tried ammonium sulphide, which acts perceptibly on 

 the phylloxera in the same way as hydrogen sulphide. He buried 

 around the roots, after having laid them bare, 500 grammes (IjV lb.) 

 per stock of a mixture of 36 parts of calcium sulphide and 66 

 parts of sulphate of ammonia. Under the influence of moisture these 

 two salts dissolve in the ground, and yield by double decomposition 

 ammonium sulphide and calcium sulphate. The result was negative. 



Melolontha vulgaris (cockchafer). — The insecticide property of 

 hydrogen sulphide has been utilized to destroy numerous injurious 

 insects, living in the soil, especially the ivJiite worm. Dr. Precht has 

 taken out a German patent to claim a process of formation of this gas 

 in the soil. Prior thereto Roy had recommended the burying in the 

 ground of cinders rich in iron sulphide. In Italy good results are 

 obtained against the white worm by ploughing in white mustard, more 

 especially mixed with one ton of gypsum per acre. The decomposition 

 of these plants would appear to produce much sulphuretted hydrogen. 



Heterodera Scliaclitii, Schm. — The ploughing in of crucifers and 

 gypsum did not give the result expected. ' 



Cochineals — Co |uillet did not succeed in destroying the cochineal 

 of the lemon by covering this tree with an awning, and disengaging 

 sulphuretted hydrogen under this improvised " cloche ".^ 



4. Sulphur, S.— Sulphur, in combination with metals and metal- 

 loids, is very widely distributed in nature. It is chiefly met with as 

 sulphides of iron, copper, lead, mercury, zinc, antimony, and arsenic. 

 Native it is found in lacustrine deposits associated with marl, and 

 especially in the precincts of volcanoes as a product derived from 

 volcanic emanations. It is found in the mines of Vesuvius of Lateria, 

 near Rome, in those of Etna and Stromboli. 



Preparation. — When sulphur forms 50 per cent of the mass in 

 which it is incorporated, it is fused in cast-iron pots at a heat not ex- 

 ceeding 140^ C. (284° F.). The fused sulphur flows into horizontal 

 retorts — exposed to the direct heat of a furnace — in which it is brought 

 to the boil and the vapours conveyed into a large masonry chamber, 



' Note bij Transla'or. — But it must not be forgotten that sulphuretted hydrogen 

 is heavier than atmospheric air in the proportion of :-57 to 31, that is, 100 cubic 

 inches of the former weigh 37 grains, and of the latter 31 grains. This difference 

 in density must retard diffusion, so that the bottom of the plant would get an undue 

 shar and the top less than its share. Instead therefore of placing the generating 

 vessel on the ground it should be at least well up the tre. 



