38 MASS. EXPERIMENT STATION BULLETIN 226. 



Dry liiiie-sulfur 72 



Sodium sulfur compound 70-72f 



Barium sulfur compound 60-64 



From' tlie above, it is evident that in tliese tests the liquid lime-sulfur 

 concentrate diluted 1:10 proved equally effective to the 1:8 strength. 

 There was a distinct falling off with, the 1:11 and 1:12 strengths, and a 

 sharp decline in killing efficiency at the 1:14 dilution. The dry liuie-sulfur 

 and sodium sulfur compound proved about equally effective, but did not 

 give quite as good a kill as the 1:12 dilution of the concentrate. The 

 barium sulfur compound fell considerably below the two others in killing 

 eft'iciency, and proved but little better than the concentrate at 1:14. 



In no case did any of the dry sulfides equal the concentrated lime-sulfur 

 solution, 1:8 or even 1:12, in killing the scale. It is evident, therefore, that 

 the dry materials must be used at strengths higher than those recommended, 

 to bring their killing efficiency up to that of lime-sulfur solution. There 

 are two drawbacks to any such plan: 



1. Any material increase in dosage will bring the co.st of the dry mater- 

 ials to a very high figure as compared to that of the lime-sulfur solution. 



2. There is experimental data to show that the efficiency of the dry 

 materials increases as the dosage grows higher, only up to a certain point. 

 Beyond this, the accumulation of insoluble matter is so great as to offer 

 difficulties in application. Straining out this insoluble matter would 

 doubtless relieve this difficulty, but would require an additional step in 

 the preparation of the spray. 



There has been for some time a feeling, which has led to considerable 

 discussion, that equal amounts of the liquid lime-sulfur and of some of 

 the dry sulfides, based on the active principles they contain, are not equal 

 in killing efficiency 



On the basis of the polysulfide sulfur content of each of the materials 

 used in these tests, we find the amount of polysulfide sulfur present in 

 .50 gallons of spray to be as follows: 



Lime-sulfur solution 



Dry lime-sulfur 



Sodium sulfur compound 



Barium sulfur compound 



Comparing these figures with the table above showing the effectiveness 

 of the materials in actual field tests, it is evident that the dry materials 

 had a killing power much nearer that of the lime-sulfur solution than their 

 polysulfide sulfur content would lead one to suppose; and further, that any 

 increased dosage should be figured on the actual performance of the differ- 

 ent materials in the field, rather than on a comparison of their chemical 

 content alone. 



It is along such a line that further work remains to be done. 



From the above tests and the information we now have on these mater- 

 ials, certain conclusions are evident: 



I. Under Massachusetts conditions, the commercial lime-sulfur solution, 



