194 SPRAYING MATERIALS 



the test supposedly varying with the amouut of sulfur iu 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 dy^ gallons of water, while the former could take 

 only 71/4 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. j\Iost hydrometers give both the 

 specific gravity and the Beaume strength. Anyone can therefore 

 tell by the use of this instrument, and by knowing 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 

 and messiness of home preparation. And this is a great deal. 

 They are also very simple to use. 



On the other hand, the buyer pays considerably more for a 

 hundred gallons of spray by this method than he does to prepare 

 his own concentrate. 



2. Home-made Concentrate. — This is the same material, in a 

 general way, as the commercial, but it does not run as high in 



