14 



MASS. EXPERIMENT STATION BULLETIN 201. 



Composition. — A comparison of home-made concentrate and the 

 commercial 33° Baume concentrate is shown in the fohowing table: — 



Home-made 



(24^° B) (Per 



Cent). 



Commercial 



(33° B) (Per 



Cent). 



Water, 



Sulfur in solution, 



Polysulfide sulfur, 



Thiosulfate sulfur, 



Ratio thiosulfate sulfur to polysulfide sulfur, 



Calcium 



Oxygen in combination, .... 



Water 



Calcium polysulfide (CaSi.so) 



Calcium thiosulfate 



75.00 

 17.00 



13.75 



3.25 



1:4.23 



24.00 



.75 



1 : 32.00 



68.04 

 24.751 



0.65 



.56 



100.00 



75.00 



17.29 



7.71 



100.00 



68.04 



30.18 



1.78 



100.00 



1 A conservative estimate. 



Stability. — Lime-sulfur is readih^ oxidized on exposure to air, the 

 polysulfide being converted into thiosulfate with precipitation of sulfur, 

 the thiosulfate into sulfite with precipitation of additional sulfur, and the 

 sulfite into sulfate, as follows : — 



CaS5+03=CaS203+S3 

 CaS203=CaS03-l-S 

 CaS03+0=CaS04 



This necessitates full containers, well-stoppered, or a thin covering of 

 jmraffin oil to prevent decomposition of lime-stdfiiT in storage. 



The guaranty of commercial concentrates is generally about 33° Baume 

 and 25 per cent sulfur in solution. The efficiency, however, is more accu- 

 rately measured bj^ the amount of polysulfide sulfur in solution, irrespective 

 of whether the effectiveness is a result of direct action or from products 

 of decomposition. The total sulfur in solution apparently gives the home- 

 made product, containing a much larger proportion of thiosulfate sulfur, 

 relatively too high a rating. 



According to P. J. Parrott, of the New York (Geneva) Agricultural 

 Experiment Station, a gallon of diluted lime-sulfur for dormant spray 

 (San Jose scale) should contain about 0.297 pound of sulfur in solution, 

 or 3.45 per cent; and for fungicidal work on foliage, 0.065 pound of sul- 

 fur, or 0.775 per cent. The following formulas are so calculated for con- 

 centrates of 15° to 36° Baume : — 



