406 



[Vol. 9 



GARDEN 



Since the origination of lime sulphur as an orchard spray by 

 M. F. Dusey of Fresno, California, in 1886, there has been a num- 

 ber of studies made on its effectiveness as a spray anc on its 

 chemical composition. The first of these of importance was by 

 Thatcher ('06). He found that lime sulphur contained for the 

 most part calcium polysulphides, calcium thiosulphate, and small 

 quantities of sulphites and sulphates. Haywood ('09), using the 

 same methods, obtained similar results. When he dried the mix- 

 ture the polysulphides disappeared and increasing amcunts of 

 precipitated sulphur were formed. He attributed the fungicidal 

 value of lime sulphur particularly to the thiosulphates and pos- 

 sibly to a combined or a summation of the toxic properties of all 

 the compounds formed exclusive of sulphur. 



Van Slyke, Bosworth, and Hedges (10) made some chemical 

 determinations of lime sulphur when the ingredients were varied. 

 They came to the conclusion that a mixture containing a high 

 proportion of sulphur had the largest amount of calcium penta- 

 sulphides and a greater fungicidal value. They proposed the 

 following formula: 80 lbs. sulphur, 36 lbs. calcium oxide, and 50 

 gallons water. This formula is the one in general use at the 

 present time. Their chemical determinations gave about the 

 same results as those obtained by Haywood ('09). Ruth ('13), 

 in a study of lime sulphur and lead arsenate mixtures, found that 

 no arsenic sulphide was formed. The proportion of thiosr lphates 

 and sulphites was increased in this mixture, and he attributed 

 the increased effectiveness of the spray to the presence of ad- 

 ditional quantities of these compounds. There was no experi- 

 mental evidence for this, and his chemical determinations did 

 not show the presence of any particular toxic compound. Harris 

 '11) made chemical determinations of lime sulphur mixtures 

 and found about the same amounts of sulphides, sulphites, etc., 

 as Haywood. He also stated that filtering was unnecessary. Of- 

 ficial methods for the determination of the compounds formed in 

 lime sulphur are given by Roark ('20) and Winter ('20). 



The above studies on lime sulphur have had to do with freshly 

 prepared mixtures. Vermorel and Dantony (19) gave a lumber 

 of reactions that probably took place in lime sulphur mixtures 

 and the compounds formed when the mixture was aerated. 

 They found that the polysulphides soon disappeared aiter the 

 spray was applied. The calcium thiosulphates gradually decreased, 

 and sulphites, sulphates, and free sulphur increased. Barker, 



