CALCIUM PHOSPHIDE. 157 



Plusia'ganmia, L. (silver Y moth). — The caterpillars of this Noctua 

 abandon plants treated by plaster. 



Melolontha vulgaris (cockchafer). — Poll recommends to kill this- 

 larva to plough in 8 cwt. of plaster per acre along vpith the cruciferous 

 plants grown for this purpose as intercalated crops. Plaster does- 

 not, however, act as such, but owing to the sulphuretted hydrogen 

 evolved by the fermentation in presence of organic matter. 



Hyper a variabilis (beet weevil). — Plaster renders the same service- 

 as lime in destroying the larvae of this insect in lucerne fields. It 

 suffices to throw a certain amount with the shovel on the infested 

 plants. The larvae of the saw-fly succumb by powdering them with 

 plaster as well as with lime (Taschenberg). 



Snails and Slugs. — Plaster used like lime destroys these mollusca. 



Rodents. — Rodents are often destroyed by plaster. It is spread 

 on a saucer and covered with a layer of flour, a second saucer is filled 

 with water. The rodents begin to eat the flour, of which they are 

 very fond, then the plaster. When they go to slake their thu-st the 

 plaster swells and agglomerates in their stomachs, causing death. 



Sulphite of Lime, CaS032HoO. — Preparation. — By treating 

 milk of lime or chalk beaten up with water by sulphurous acid. 



Properties. — Sulphite of lime only dissolves in 800 times its weight 

 of water, but it is very soluble in sulphurous acid with which it forms 

 calcium bisulphite. 



Use. — Dufour tried sulphite of lime against the Dematojihora 

 necatrix, Hartig. (white root rot), but he did not find it effectual 

 J. de Sokolnicki used with success against the Botrytis cinerea, Pers.. 

 (grey rot of the vine) a powder of the following composition : alumed 

 plaster 20 lb., bisulphite of lime 10 lb., Portland cement 15 Ib.^ 

 hydraulic lime 20 lb., gi-een vitriol 35 lb. This powder used on vines- 

 from 8 May and during flowering kept the grapes free from rot. 

 It is, moreover, known that bisulphite of lime destroys moulds because 

 it is regarded as the best disinfectant for cellars infested with mould. 

 It is also used to destroy the cryptogams which infest dairies, and 

 for the preservation of beer. It is to be remarked that the mixture 

 used against the black rot does not act solely through the bisulphite 

 of lime, but rather by the alum. 



48. Calcium Carbide, CaC,. — Preparation. — By acting on an 

 intimate mixture of quicklime and powder, with the high temperature 

 of the electric furnace. 



Properties. — It forms hard, compact scoriaceous masses without 

 smell in dry air. In moist air it gives off an alliaceous odour. 

 In contact with water it disintegrates and decomposes into hydrate 

 of lime and acetylene 



Use. — See acetylene. 



49. Calcium Phosphide, Ca^P.^. — Preparation.— By passing the 

 vapours of phosphorus over sticks of chalk heated to redness. 



Properties. — Calcium phosphide decomposes into water and lime, 

 and into phosphuretted hydrogen, a poisonous gas. 



Use. — Mouillefert used this substance with the object of destroy- 

 ing the phylloxera. For this purpose he exposed some roots infested. 



