REPORT OF THE CEEMIST 153 



SESSIONAL PAPER No. 16 



ing methods of preparation have appeared. This has given rise to inquiries as to the 

 best mode to adopt in making the spray. To answer these the more satisfactorily, we 

 have made a series of experiments, using the quantities and methods of procedure 

 advocated by the more important authorities, and as a result have obtained information 

 on one or two points that may be of interest to orchardists. 



1. Since the insecticidal and fungicidal properties of the spray appear to be due to 

 sulphide of lime and not to free (uncombined) sulphur or lime, it is desirable on the 

 grounds of economy and efficiency that the proportion of sulphur to lime should be such 

 that after boiling there may be little or no free sulphur in the mixture. We find to 

 ensure this that the quantity of lime should at least equal that of the sulphur. A 

 slight excess of lime apparently does no harm, indeed, according to some authorities, it 

 is necessary in order to give the spray the correct consistency, but too large an excess 

 is certainly to be avoided, as it will be apt to cause clogging of the nozzle and possibly 

 reduce the insecticidal efficiency of the wash. We have found the following proportions 

 satisfactory : — 



Lime .... 25 lbs. 



Sulphur 20 " 



Water 50 gallons. 



We also tried a formula with a larger excess of lime and obtained a good result, 

 though possibly not quite so strong in insecticidal properties ; — 



Lime 35 lbs. 



Sulphur 15 " 



Water 50 gallons. 



2. The lime should be thoroughly slaked to avoid subsequent clogging of the nozzle. 

 If part of the lime is added after the spraying mixture is made, as directed in some 

 recipes, the proportion of lime to sulphur in the mixture as boiled should not be less 

 than that indicated in the, first formula given above. 



3. It is essential that the boiling should be continued a sufficient length of time to 

 allow all the sulphur to enter into combination. This, if accompanied by constant 

 stirring, will be usually between 2 and 3 hours. 



4. The addition of salt (usually at the rate of 15 lbs. to each of the foregoing 

 formulae) is recommended by all writers. This may be due to its alleged action in 

 increasing the adhesive qualities of the spray. It does not seem to affect its properties 

 otherwise. 



5. On cooling certain of the lime sulphides formed crystallize out. It is, therefore, 

 important, we consider, to make the application while the mixture is still hot. 



The addition of Potash to the California Spray. — It was suggested that potash might 

 be a valuable addition to this spray, enhancing its value probably both as an insecticide 

 and fungicide. W^e accordingly made some laboratory experiments and found that by 

 the addition of potash to the spray, the lluid which is essentially sulphide of lime is in 

 part decomposed thereby, lime separating and sulphide of potash, soluble in water, 

 taking its place. It is quite possible that the latter compound is as effective as sulphide 

 of lime, but we have no data on that point. For effectiveness and ease of application 

 it is apparently essential that the spray should be used while still hot and, under such 

 circumstances, the addition of the potash would not in all probability, materially affect 

 the application. But if the spray became cold the separation of the lime by the 

 addition of the potash would undoubtedly increase the tendency to clog in the nozzle. 



