CHAPTER XVI 

 INSECTICIDES, FUNGICIDES, ETC. (continued) 



PARAFFIN AND PARAFFIN EMULSIONS (Reports, VI, 16, 135, 

 196; VIII, 18; X, 7,13) 



(i) Their nature, and their effect on trees. 



Kerosene, or paraffin oil, was used for the treatment of trees 

 almost as soon as it came into use for lighting purposes. The 

 first definite recommendation for its application to plants seems 

 to have been made in 1865, the object being the destruction of 

 scale on orange and other trees. 



Under the name of paraffin, as commonly understood in this 

 country, we may be dealing with a variety of mixtures of some 

 20 or more different chemical compounds, these mixtures differing 

 from each other very widely as regards composition and essential 

 properties. With the exception of certain oils obtained in Scot- 

 land and elsewhere by the distillation of shale to be avoided 

 by fruit growers, as containing sulphur and other compounds, 

 which would probably be injurious to their trees the paraffins 

 on the market are natural products imported from America, 

 Russia, Roumania, Borneo, etc., and consist chiefly of compounds 

 of carbon and hydrogen belonging to one particular series of 

 hydrocarbons, known scientifically as the paraffin series. The 

 most volatile of them include benzine, naphtha and petrol, 

 which contain little or no oil with a boiling point higher than about 

 150 C. : the least volatile include such substances as vaseline, 

 petroleum jelly, paraffin wax, and some lubricating oils : the 

 intermediate class include the oils known as lighting oils, petro- 

 leums, kerosenes, solar distillates, etc. ; these vary considerably 

 in composition, from oils which distil entirely below 300 C. to 

 others of which only a fraction will distil below this temperature. 

 Even if the fruit grower confines himself to the oils of this 

 intermediate type, he may be using one which is so volatile that 

 it does not remain on the trees long enough to do any good, or 

 else one which contains so large a proportion of non-volatile 

 constituents, that the result will be much the same as if he had 



