INSECTICIDES, FUNGICIDES, ETC. 



When a fungicidal action is not required, the above recipe 

 may be altered to 



Iron sulphate . . . . J Ib. 



Quicklime . . . J Ib. 



Water . . . . . 9! gallons 



Paraffin . . . .5 pints 



Caustic soda . . . . 2j Ibs. 



Both these emulsions may be made in a concentrated form 

 (ten times the above strengths), requiring dilution and the 

 addition of the caustic soda before use. 



The iron in the iron emulsion, after it is sprayed on to the 

 trees, oxidises, and becomes brown, but this does no harm 

 whatever. 



When speaking of a detergent action on fruit trees, it must be 

 remembered that something different is meant from a detergent 

 action on the human body, etc. In the former case, the cleansing 

 refers to the removal of moss, lichen, dead bark, etc., and for 

 this a caustic alkali is required; in the latter, it refers to the 

 removal of grease and dirt, in doing which soap is most effective. 

 The detergent action of soap is attributable to several causes, 

 and one of those most recently brought to light * is its power of 

 actually dissolving and combining with oils; soft soap, when 

 worked with paraffin, etc., will absorb as much as its own weight 

 of the oil, and, when the resulting magma is left with water, 

 part of the oil separates as an emulsion, but part (sometimes the 

 whole of it) goes into actual solution. It is improbable that in 

 the case of spray-fluids sufficient oil is dissolved to affect the 

 action of the fluids, but the possibility that it may be so should 

 be borne in mind when considering their effects. 



In a patent insectide, known as paranaph, it is claimed that 

 the addition of naphthalene to soap increases the power of the 

 latter to take up paraffin, and that, on adding water, a very 

 superior emulsion is obtained. It was found, however, that 

 such statements were not supported by facts ; that the greater 

 part of the naphthalene which dissolves to a certain extent 

 in soft soap separates out on dilution, and that its presence 

 actually reduces the amount of paraffin remaining in solution. 



(4) Nature of the action of paraffin. 



How paraffin acts on the cells or tissues of vegetables or insects, 



1 Pickering, Trans. Chem. Soc., 1917, Vol. Ill, p. 86. 

 M 



