SELECTING AND PREPARING MATERIALS 



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sulfur, as it is often called, is well standardized. It is avail- 

 able from many commercial concerns, being supplied usually 

 in drums or barrels holding 50 gallons. Its strength is deter- 

 mined by means of the Baume test, the instrument employed 

 being the hydrometer. This records the density or specific 

 gravity of the solution. The commercial product should test 

 at least 32° Baume; it frequently tests 33°. There should 

 be no sludge or precipitate in the bottom of the barrel. 



a : 6. Dry lime-suljur is obtained by dehydrating or ex- 

 tracting the moisture from concentrated lime-sulfur containing 

 some stabilizer, like cane sugar. It is mixed with water before 

 using. It is cheaper to transport and easier to handle than 

 concentrated lime-sulfur. It is not so powerful an insecticide 

 at the strengths recommended by the manufacturers as con- 

 centrated lime-sulfur, and at present prices is more expensive 

 on the basis of active ingredients. It seems necessary to use it 

 in larger amounts for effective results than the manufacturers 

 recommend at present. 



a : 7. Tobbacco preparations are valuable contact insecti- 

 cides. Nicontine is the effective agent. It is a powerful, 

 quickly acting poison, very toxic to many insects. These 

 preparations may be used on tender foliage without injury. 

 They are employed extensively for the control of aphis and 

 red bug. 



The common commercial form is a concentrated solution 

 containing 40 percent of nicotine sulfate; other preparations 

 containing different proportions are also available. 



The value of nicotine sprays is affected largely by tern-' 

 perature changes and the hardness of the water used for dilu- 

 tion. They function best at warm temperatures and when the 

 air is quiet enough so that the fumes generated do not dissi- 

 pate rapidly. Hard water increases the toxic effect of the 

 application. Soap is often added to increase the spreading 

 properties of the material. 



Most nicotine trade names give an indication of the per- 

 centage of nicotine present, for example ^^Black Leaf 40." 



