PETEOLEUM SPIEIT. 307 



cent of soap, Fernald that of an emulsion containing quassia. 

 Emulsions of 3-4 per cent containing a little suspended sulphur are 

 also recommended. 



Phytojytides. — To destroy them action must be taken the moment 

 they invade the buds, that is to say, at the moment the acari are 

 grouped around these. This treatment is especially used in South 

 America where acari cause frequent ravages. 



III. Petroleum Spirit. — Preparation. — Petroleum spirit is 

 rectified petroleum, collecting by distilling the hydrocarbides boiling 

 between 100" and 150" C. (212-3i.2' R). 



Action on Plants. — Petroleum spirit is regarded as less injurious 

 to the tender parts of plants than petroleum oil ; applied by spraying 

 on the plant it evaporates more rapidly and the plant does not re- 

 main so long in contact with it. 



Action on Insects. — Petroleum spirit appears less active on ■ 

 insects than petroleum oil, and it must be used in larger doses than 

 the latter. Used in the soil, its radius of action is more extended, 

 which renders it more apt to overcome underground insects. 



Use. — Alvood and Slingerland tried to replace petroleum oil 

 emulsions by petroleum spirit, but they found the latter inferior. 

 Mohr, on the other hand, reports the good services rendered against 

 underground parasites by the following emulsion : — 



Mix together 2^ lb. of oleic acid and 2^ lb. of ammonia, then add 

 1 gallon of petroleum and 1 gallon of petroleum spirit. By an intimate 

 mixture made by a spraying machine a stable emulsion of syrupy 

 consistence is obtained. For the destruction of underground parasites, 

 such as nematodes, larvae of melolonthides, noctua wire-worms, mole 

 crickets, etc., 1 gallon of this emulsion is mixed with 20 gallons of 

 water. The dilute emulsion contains about 4 per cent of petroleum, 

 and behaves in the same way as the ordinary emulsions of soap and 

 petroleum. To obtain complete destruction Mohr says it is not 

 enough to spread the preparation in the soil ; holes must be pierced 

 every 20 centimetres (8 inches), 30 centimetres (12 inches) in depth, 

 and into which 20-30 cubic centimetres of emulsion, say up to a fluid 

 ounce, are poured ; then the holes are plugged. 



CeutJiorhynchus sulcicollis, Gyl. (cabbage weevil). — Underground 

 injections of diluted Mohr's emulsion kill it, also the following : 

 Otiorhynchus s^dcatuf; (vine weevil) ; Molytes corojiaius, L., weevil 

 injurious to beets, because it perforates their leaves. 



Gonchylis ambiynella (cochylis of the vine). — Del Quercio advises 

 an emulsion of 1 per cent petroleum and 1 per cent of soft soap. 

 Caruso got excellent results by a bouillie of 2 per cent petroleum 

 spirit, 3 per cent soft soap, and 0-5 per cent alcohol. As for petroleum 

 emulsions, this emulsion must be made ten times more concentrated, 

 and diluted at the time of use by hot water. By applying this emul- 

 sion on the caterpillars, Martini destroyed 94 per cent, whilst Dufour's 

 pyrethrum bouillie only destroyed 79 per cent, and rubinia (wood tar) 

 of 5 per cent strength only 73 per cent, 



Tingis Piri. — Del Quercio describes the good effects of an 

 emulsion of petroleum 1 per cent and soft soap 1 per cent. 



