300 INSECTICIDES, FUNGICIDES, AND WEED KILLERS. 



and Kruger, should never be exceeded if trie emulsions are to be used 

 on the tender parts of plants. Schoyen asserts that they do not 

 damage the leaves, especially when the composition is unimpeachable. 

 Generally dilute and homogeneous emulsions are made when about 

 to be used ; the following are some proportions recommended : — 



These four emulsions are very stable and can be kept. They are the 

 best. Petroleum and soap emulsions have entirely replaced those of 

 milk and petroleum. They are in current use in America. 



6. EnmUion of Petroleum ivith Fish Oil. — -There are emulsified 

 together at 60° C. petroleum 15 lb., fish oil 2} lb., water 15 gallons. 



7. Petroleum and Milk Emulsion. — Curdled milk forms perfect 

 emulsions with petroleum (Barnard, 1891) : 2^ gallons of turned milk are 

 diluted with 10 gallons of hot water, then 20 gallons of petroleum are 

 added with constant stirring. Ten gallons of petroleum and 5 gallons of 

 curdled milk can also be emulsified together. If it be desired to use fresh 

 milk a little vinegar must be added. Sorauer prepares the fresh milk 

 emulsion although it is not made so easily. To obtain a perfect emul- 

 sion the liquid to emulsify must be drawn in and expelled for three- 

 quarters of an hour, if the mixture be at 16° C, during fifteen minutes 

 at 24° C. (Hubbard). This emulsion is diluted with twenty times its 

 volume of water before use. The stability of this concentrated 

 emulsion is less than that of a petroleum and soap emulsion. Unless 

 it be kept in vessels absolutely closed it spoils in eight to fifteen days. 

 According to Cooke, plants suffer more from this preparation than 

 from petroleum soap emulsions. 



8. Petroleum Emulsion containing Insecticides and Metallic 

 Salts. — By adding to petrolo-saponaceous emulsions either extract 

 of hellebore, arsenite of copper, or any other poisonous substance, the 

 effect of the emulsion is strengthened and a more desirable action ob- 

 tained. An emulsion, for example, is made with petroleum \ gallon, 

 soft soap 7-^ lb., hellebore 2^ lb., water 100 gallons. Smith advises 

 the addition of 2\ per cent of petroleum to a cupro-arsenical bouillie. 

 The bouillie is stable, and the petroleum remains longer in fine division 

 on the leaves than in pulverizing ordinary emulsions. According to 

 the sensitiveness of the plant or the resistance of the insect submitted 

 to the action of this bouillie, the dose of petroleum is increased or 

 diminished. Kruger advises an emulsion made with equal parts of 

 petroleum, soft soap, and water, to which quassia or tobacco juice is 

 added. Diluted before use with ten to twenty times its volume of 



