158 INSECTICIDES, FUNGICIDES, AND WEED KILLERS. 



by this insect in a 2-litre flask. Then he introduced 0-2 grammes of 

 calcium phosphide which slightly moistened gave 20 cubic centimetres 

 of phosphuretted hydrogen. This atmosphere contained 1 per cent of 

 asphyxiant gas, and was capable of killing the phylloxera in fourteen 

 hours. The numerous trials which were made on plants in pots and 

 on the large scale led Mouillefert to the following conclusion : — 



Phosphide of calcium by the phosphoretted hydrogen which 

 it gives otf in decomposing, may kill the phylloxera when the insect 

 is exposed to its action in an open, short-necked bottle, although, 

 however, this substance may be much less energetic than potassium 

 cyanide and carbon disulphide. But used on phylloxera-infected 

 vines, in pots or in vineyards, this phosphide has, so to speak, no 

 action on insects, which is probably due to the deleterious gas being 

 rendered harmless by the air and by the soil which burns it, and con- 

 verts it into products without action on the phylloxera. 



50. Arsenite of Lime, CaoAs,Or,. — Preparation. — The paste of 

 arsenite of lime used to destroy injurious insects is made by dissolving 

 1 lb. of white arsenic in 2 gallons of water, and running into the 

 solution a milk of lime containing 2 lb. of lime. The mixture is then 

 heated for half an hour then thinned to make 100 gallons of bouillie. 

 The arsenite of lime formerly used was the residue from the manu- 

 facture of magenta ; it consisted largely of arsenite and arseniate 

 of lime, and was sold under the name of London purple. As it 

 was partially soluble in water it was necessary to add to it to 

 render it harmless to plants an equal amount of quicklime under the 

 form of milk of lime. In America they have even used a paste con- 

 sisting of 60-120 grammes of London purple and l'0-2'5 kilogrammes 

 of lime in 100 litres of water. ^ 



Properties. — Arsenite of lime is insoluble in water. The pre- 

 cipitate is light and keeps in suspension much better than the arsenite 

 of copper. It has the advantage of being cheaper than Scheele's green 

 and emerald green (Paris green), this is especially so as regards London 

 purple, but the latter is variable in composition and its action on insects 

 is comparatively weaker. Arsenite of lime owing to its insolubility in 

 water is much more harmless to plants than arsenite of copper. 

 Whitehead found the following doses harmless : — 



4.5 grammes of purple in 100 litres for apple-trees.' 



,50 ,, ,, pear and cherry-trees. 1 



00 ,, ,, the plum, hazel, and cherry-trees. 1 



The bouillie made with an excess of milk of hme is, so to speak, hai-m- 

 less to plants. 



Use. — Arsenite of lime is used wherever arsenite of copper is 

 capable of destroying injurious insects. Arsenite of lime has the ad- 

 vantage over arsenite of copper that it may be associated with eau 

 celeste (p. 260 et seq.) without dissolving therein. The bouillie thus 

 obtained is one of the most efficient in simultaneously combating 

 the following injurious insects and fungi : — 



' Note by T7-a7islator. — Gvammes per 100 litres — parts by weight per 100,000 

 parts by volume or lb. per 10,000 Imperial gallons. 



