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A COPPER EMULSION AS A FUNGTCTDE. 



By H. WORMALD and L. K. WORMALD. 



{Research Defartment South-Eastern Agricultural College, Wye, Kent.) 



(With Plate XT.) 



In the report of the Agricultural and Horticultural Research Station, 

 Long Ashton, for 1917, A. H. Lees described methods of preparing an 

 emulsion containing copper by mixing a solution of copper sulphate 

 with soap solutions. 



In conjunction with other experiments, a very similar emulsion was 

 made and used at Wye early in 1917. Since the observations made at 

 Wye as to the nature of this emulsion corroborate those of Mr Lees, 

 and since additionally the fungicidal properties of this emulsion have 

 been examined, it seems desirable to record the work so far done, 

 although further experiments must be carried out before an emulsion of 

 this kind can be recommended as a practical spray fluid. 



The emulsion prepared at Wye contained rather mora copper than 

 that made by Mr Lees. It contained the equivalent of 0-4 per cent. 

 copper sulphate (CUSO4 . SHgO) and 2 per cent, of soft soap^ and was 

 made by pouring slowly a 0-8 per cent, solution of copper sulphate 

 into an equal volume of 4 per cent, soft soap solution, stirring well all 

 the time. The emulsion made in this way did not settle, even on standing 

 for several weeks; it could not be filtered and turned chocolate colour 

 on addition of potassium ferrocyanide. When the soap solution was 

 added to the copper solution a quite different result was obtained, and 

 instead of an emulsion (probably of copper stearate in part) green 

 sticky masses having a putty-like consistency were formed. 



Li order to determine whether the emulsion made as above described 

 possessed fungicidal properties, the following experiment was carried 

 out on August 8, 1917. 



Fresh potato shoots were brought into the laboratory, cut under water 

 and placed with ends in water in flasks the mouths of which were under 

 water. On each of two shoots, three leaves at successive nodes were 



1 The soap used throughout these experiments is that sold under the name of 

 "Chiswiek Soft Soap." 



