EXPERIMENT STATION BULLETINS. 



307 



calcimn may combine with one, two, three, four or five elements of sulfur. 

 Under the conditions that exist in the manufacture of the lime-sulfur 

 spray, most of the lime and sulfur combine in the proportion of 1 to 5, 

 forming a compound known as the penta-sulfide of calcium. If all of the 

 calcium and sulfur combined in this proportion, then in the process of 

 making the spray, the calcium and sulfur should be used in the pro- 

 portion of one part of the former to four parts of the latter by weight or 

 1.4 parts of lime to 4 of sulfur. Other compounds are formed, however, 

 in the process and we find by calculation that the theoretical amounts 

 of lime and sulfur that should be used to form the greatest amount of 

 penta-sulfide are one part of lime to 2.28 parts of sulfur by weight. The 

 commercial brands of lime are very seldom pure calcium oxide, as they 

 contain varying amounts of magnesium oxide which reduces the 

 efficiency, and we find that the proportion of one part of lime to two 

 parts of sulfur by weight gives the more satisfactory results. 



That the insecticidal value of the solution is due chiefly to the penta- 

 sulfide or higher polysulfides of calcium has been quite definitely estab- 

 lished, and it is not probable that the other compounds formed possess 

 any insecticidal or fungicidal value. Consequently in the discussions 

 and tables which follow, only the total sulfur in solution and the amount 

 of sulfur in sulfide form will be considered. 



The first point to be considered was that of the composition of some 

 of the limes found upon the Michigan markets. The following brands of 

 lime were used : 1 — Kelly Island Lime. 2 — A special low magnesia lime 

 put out by the Michigan Lime Co. 3 — Crescent Brand of Lime. 4 — Ohio 

 and Western Go's Lime. 5 — Kelly Island Lime and Transport Co's Lime 

 from White Rock, Ohio. 6 — Bay Shore Superior Lime. 



These limes showed the following analyses for calcium oxide and 

 magnesium oxide. ' 



With two exceptions, two batches of lime-sulfur solution were made up 

 from each brand of lime, one according to the formula 60 pounds of lime 

 125 pounds of sulfur and GO gallons of water, designated by the letter A 

 in column one of the table below, the other according to the formula 

 50 pounds of lime, 100 pounds of sulfur and 50 gallons of water, designated 

 by the letter B. 



The solutions were made in barrel lots in a wooden tank built for the 

 purpose. Steam at 45 pounds pressure was used as the boiling agent 

 and the solutions were boiled for one hour. Allowance was made for 

 condensation of the steam so that the volume of the solution at the end 



