MATERIALS 55 



it also varies considerably in efficiency with small 

 variations in the details of its manufacture, so that it 

 is never likely to become popular in England. 



23. Liine-siilpJiur-soda-salt wash {Oregon wash). — 

 This is a modification of the above, in which i lb. of 

 caustic soda is used in addition to the other compounds, 

 the result being that more heat is developed, the 

 mixture boiling, and the chemical change becoming 

 complete without the aid of external heating. The 

 soda and lime are mixed together, and are slaked 

 with hot water, in which the sulphur has previously 

 been incorporated. If, however, the actual amount of 

 solids taken is not considerable (about 20 lbs.), the heat 

 generated has generally to be supplemented by external 

 heating. 



The sulphur in this case appears to combine with 

 the caustic soda to the exclusion of the lime, and it is 

 a question whether the lime could not be dispensed 

 with altogether. Probably, however, it is of impor- 

 tance in forming with the sulphur an adhesive deposit 

 on the trees. The caustic soda might well be in- 

 creased to 2 lbs., or even 3 lbs., to make the wash 

 more effective for removing moss, etc. 



24. Sulphide of potassium {Liver of sidpJiur). — This 

 is used as a fungicide, and it is specially valuable for 

 mildews, such as the gooseberry mildew ; it is very 

 efficient, however, for aphis, especially when used in 

 conjunction with soap. The proportions recommended 

 are — 



(24^) Potassium sulphide . . 3 to 10 ozs. 

 Water . . . .10 galls. ; 



