194 SPRAYING MATERIALS 



many growers are using them to the exclusion of most other 

 sprays. There are four forms which it seems worth while to 

 discuss at some length. 



1. The Commercial Lime-sulfur Solutions. These come as 

 more or less clear, amber-colored liquids which mix readily with 

 water, giving a yellow liquid. They come at various strengths, 

 varying about 30 to perhaps 35 Beaume (hydrometer test), 

 the test supposedly varying with the amount of sulfur in solu- 

 tion. As a matter of fact a handful of salt or various other 

 cheap materials will raise the strength as indicated by this 

 hydrometer test just as surely as more sulfur will, so that the 

 only reliable standard is the per cent of sulfur in solution. 



In preparing these commercial lime-sulfur sprays for use 

 in the orchard the common method is to dilute them by taking 

 a certain number of gallons of water to each gallon of the con- 

 centrate. This is not a reliable method because, as already sug- 

 gested, the concentrate may vary from 30 to 35 Beaume. The 

 latter would give the proper strength for San Jose scale by 

 diluting with 9y 2< gallons of water, while the former could take 

 only 7y 2> gallons of water to each gallon of the concentrate. 



A hydrometer should therefore be used to test the concen- 

 trate and again to test the spray when ready to apply to the 

 trees. The hydrometer is a simple instrument, consisting of a 

 graduated glass tube weighted with shot at the lower end. 

 This is immersed in the liquid to be tested and the lighter the 

 liquid the more deeply the hydrometer sinks. The reading 

 is taken at the surface of the liquid. Most hydrometers give 

 both the specific gravity and the Beaume strength. Anyone 

 can therefore tell by the use of this instrument, and by know- 

 ing what strength he should have for a certain pest, just 

 exactly how much water to use, provided that he has confidence 

 in the manufacturer and knows it is sulfur and not salt in the 

 solution. This is quite a proviso, but most manufacturers, no 

 doubt, intend to be honest and if the buyer selects a reputable 

 brand he is not likely to get into any serious trouble. 



The Saving and the Cost. The great advantage of the com- 

 mercial lime-sulfur solutions is that they save all the annoyance 



