October, '12] SAFRO: LIME SULPHUR WASH 387 



one to 30 with arsenate of lead added at the rate of four pounds to 

 100 gallons of the diluted spray. The fourth lot was treated with a 

 5% solution of calcium polysulphides containing a slight amount of 

 CaS203, furnished by Prof. H. V. Tartar, of the Oregon Experiment 

 Station. The eggs were treated on the day collected. 



Results with Unsprayed Apples. As a check, ninety-three eggs 

 were left untreated in the laboratorj'. Of these, ninety hatched, one 

 was accidentally crushed and two failed to hatch ''due to natural 

 causes." 



Notes on the Appearance of the Developing Eggs. It was noted, 

 in recording the appearance of the eggs, that of the twenty-six white 

 eggs in the lot, only five showed a red ring before the appearance of 

 the black spot. The eggs recorded as having a red ring showed all 

 variations from the merest trace of red to a deep red circle, many 

 shownng but fractional rings. In one case (35 a) the- egg hatched 

 without the black spot becoming visible through the chorion. Addi- 

 tional data in the tables are included as records on development. 



Lime-sulphur Wash (30° B.) 1-30. One hundred eggs were treated 

 with a one-to-30 dilution of clear lime-sulphur testing 30° B. Of this 

 number 85 hatched, one was accidentally killed and 14 failed to hatch 

 due to other causes. This fourteen percent includes, undoubtedly, 

 some "natural" and "accidental" mortality. Deducting these latter 

 items — or even ignoring them — the lime-sulphur mortality amounts 

 to very little indeed. Were every codling moth egg in an orchard hit 



fact that a specific gravity determination of a lime-sulphur solution is really a reading 

 of two (at least) solutions of unknown densities, present in unknown proportions, 

 and of radically different degrees of chemical activity. These two solutions are the 

 calcium polysulphides (CaS4 and CaSs) and the calciimi thiosulphate (CaS203). 

 Of these solutions the polysulphides are by far the most active, chemically, and 

 undoubtedly the most important insecticidal ingredient in lime-sulphur. 



The length and rapidity of boiling and coohng the spraj' are important factors 

 causing the variation in proportion of calcium thiosulphate to the calcium poly- 

 sulphides, the proportion of polysulphides increasing with the length of boiling and 

 the thiosulphates increasing with the rapidity of coohng. The knowledge of the re- 

 sulting density of the solution gives no definite idea of its chemical nature. Of the 

 two solutions, the one lower in density may be much more active due to the larger 

 amount of polysulphides present in proportion to the thiosulphate. For the same 

 reason a dilution of one concentrate may be fuUy as effective as a "stronger" dilution 

 of another. The bearing of this problem on the occiu-rence of spray injury to the 

 foliage is discussed by the author in a forthcoming pubhcation. 



The nearest approach, at present, to a logical determination of the "strength" 

 of hme-sulphur is a statement of the amounts present of calcium polysulphide and 

 calcium thiosulphate. The author used a 5% solution of calcium polysulphide 

 as a more certain test in addition to "a one-to-30 dilution of lime-sulphur testing 

 30° B." 



