16 



It will be noted that salt is not given in any of the above formulae. 

 The American bulletins nearly all recommended its use, but in the prelim- 

 inary experiments conducted in this Province by Mr. G. E. Fisher, it 

 was concluded that the presence of salt added to the cost, made the wash 

 more difficult to spray, and increased its corrosive action on the metal 

 parts of the pump ; while it failed to be any more effective as a destroyer 

 of scale, or more adhesive to the bark of the tree. Following- these con- 

 clusions, no salt has been used in the washes in this Province. 



Prof. Lochhead lately stated that, "My observations incline me to 

 believe that the presence of the salt renders the wash more adhesive, and 

 hence more effective." This is still an unsettled point; but it is evident 

 that anything which will improve the adhesiveness of the wash will in- 

 crease its effectiveness. 



Recently Mr. J. K. Haywood reported the results of a chemical 

 study of the lime-sulphur washes.* In this work it was found that when 

 the wash was prepared according to the following formula : lime, 10 

 pounds; sulphur, 6f pounds; salt, 5 pounds, and water, 20 gallons, it 

 was found that a 60 minute period of boiling was 

 sufficient to get practically all sulphur in solution. But 

 when the wash was prepared as follows: lime, 10 pounds; 

 sulphur, 6f pounds; caustic soda, 3^ pounds; salt, 5 pounds, and water, 

 20 gallons, and the ingredients put together according to directions 

 given above for lime-sulphur-caustic soda wash, about 8 per cent, of 

 the sulphur remained undissolved. Yet when the wash prepared as 

 above is allowed to cool somewhat and then heated so as to bring it to 

 the boiling point in 20 minutes, it was found that practically all the 

 sulphur was in solution. Further, it was found that so far as the 

 sulphur acids were concerned, it was the same as the wash prepared by 

 the boiling process, only that the sodium salt of the sulphur acids instead 

 of the calcium salts are formed and that it is more caustic. The investi- 

 gation failed to prove that the added salt materially affected the compo- 

 sition of the wash. 



This investigation also proved that when these washes are exposed 

 to the air, the various sulphides formed in preparing the mixture are 

 slowly oxidized through thio-sulphates, sulphites into the inert sulphates, 

 and that sulphur is liberated. In this respect the action was the same 

 whether caustic soda was used in the preparation or not. It seems quite 

 probable that the beneficial action of these washes is due to the finely 

 divided sulphur gradually liberated and to the action of the sulphides 

 and sulphites formed. 



All these washes must be applied while still warm, as when the 

 solution cools many of the compounds are precipitated. This is because 

 cold water will not hold as much in solution as the hot ; consequently, 

 if strained cold the efficiency of the mixture is weakened. 



* Journal American Chem. Society, Vol. XXVII, No. 3, 1905. 



