4 BULLETIN 451, U. S. DEPARTMENT OF AGRICULTURE. 



sulphid in cold dilute solution. Despite the intimate contact of the 

 materials for 10 days and the high plus reaction figure at the end, the 

 analytical figures for the various forms of sulphur were only slightly 

 affected, and the value of x in CaS x was reduced from 4.81 in sample 

 G-2 only to 4.45 in sample G-3. Therefore for horticultural spray- 

 ing purposes it appears that lime may be added to the diluted solu- 

 tions shortly before use without seriously affecting the various sul- 

 phur compounds. 



After completion of the preliminary experiments on the effect of 

 storage, the main investigation could be undertaken on the effect 

 produced by varying formulas and conditions. 



EFFECT OF VARYING LIME-SULPHUR RATIO. 



EXPERIMENT 3. 



Here lime was the only variable, the amount of sulphur and water and the 

 period of boiling being maintained constant. The concentrated solutions were 

 prepared as described under experiment 1, and, in fact, the majority of them 

 were the same samples, as shown by the identification letters. All determina- 

 tions were made on freshly prepared dilutions of concentrates which had been 

 stored not less than two months after decantation from sediment, except in 

 case of sample G, stored for 33 days. The results are given in Table 2. 



With increasing proportion of lime the percentage of thiosulphate 

 sulphur increases throughout, but the parallelly increasing percentage 

 of monosulphur, together with other analytical values, drops after 

 passing Preparation D merely on account of deposition of poly- 

 sulphid in crystalline form, as is well known to occur sometimes in 

 preparations made with an excess of lime. Polysulphur reached its 

 maximum value at the lime-sulphur ratio 0.45 in Preparation B, as 

 did also total sulphid sulphur, although total sulphur continued to 

 make a very slight further gain. But probably the most illuminat- 

 ing results are shown by the analytical ratio of total lime to total 

 sulphur. Equal utilization of lime and sulphur begins with Prepara- 

 tion B, where the analytical ratio 0.450 comes out exactly the same as 

 the formula ratio. An excess of sulphur over that ratio, as in Prepara- 

 tion A, produced no higher polysulphid and simply was not utilized. 

 With increasing lime-sulphur ratio equal utilization of lime and 

 sulphur continues certainly into the close vicinity of the ratio 0.500, 

 though at that point results begin to be obscured by the deposition of 

 crystals. But increased ratio means a lower polysulphid, as is clearly 

 shown. 



For each molecule of thiosulphate formed in the reaction there 

 was produced an average of about 1.84 molecules of polysulphid. 

 The individual variations from the average seem in no way to be 

 consistently dependent upon variations in formula. This ratio will 

 be discussed later. 



