18 MASS. EXPERIMENT STATION BULLETIN 201. 



(1) Emulsions. 

 The idea of combining soap, kerosene and water to form a stable mixture 

 which could be safely applied to foliage undoubtedly occurred to growers 

 ^•ery early. The first record of successful accomplishment, however, was 

 in 1S70 (26). Cook (27) records the attaining of a successful emulsion in 

 experiments in 1877-78, and the formulas which he developed, bearing 

 his name, were used for many years. The experiments of Riley and Hub- 

 bard, covering a number of years, carried forward this idea of a permanent 

 mixture of kerosene and soap, and finally led to the production of the 

 formula (28) which is used practically unchanged at the present day. This 

 formula is as follows : — 



Kerosene, ........ 2 gallons 



Water (soft), ....... 1 gallon 



Soap, ......... i pound 



The soap is dissolved in boiling water, and while the mixture is still hot 

 the kerosene is added. The mixture is then churned, \\'ith a bucket pump 

 with nozzle turned back into the liquid, until it has reached the consist- 

 ency of a thick cream. Upon cooUng, tliis thickens still further, and if 

 properly made no free oil should separate out on the surface. This stock 

 emulsion should last for some time, but it is much better to make it up 

 only as needed. Wliere the water is hard it must be softened by the addi- 

 tion of borax or soda to prevent the lime or magnesium present from com- 

 bining with the soap, which makes impossible an emulsion \\'ith the oil. 



For spraying, dilute with 9-10 parts of water for aphids or other soft- 

 bodied insects. Greater strengths are sometimes recommended for more 

 resistant insects, or on trees when dormant. 



Kerosene emulsion cannot be used safely in combination with other 

 sprays (lead arsenate, lime-suKur, etc.) owdng to the breakdown of these 

 materials in the presence of the soap, and the consequent libei-ation of free 

 oil as well as other products of this double decomposition, which are 

 dangerous to plants. This spray has now been largely superseded by the 

 various nicotine solutions which have proved fully as efficient, are more 

 easily prepared, can be used with safety to foliage, and, moreover, can be 

 used in combination with other sprays, thus saving the trouble and expense 

 of separate applications. 



Carbolic Acid Emulsion. — This is a fairly effective remedy for certain 

 root-feeding insects, such as root maggots of onion, cabbage and turnip. 

 Its value for other purposes is somewhat limited. It is made as follows: — 



Soap, ......... 1 pound 



AVater, ......... 1 gallon 



Crude carbolic acid, . . . . . .1 pint 



This is prepared in the same way as is kerosene emulsion. It will not, 

 however, attain the same curd-like consistency on standing as will kerosene 



