COMPOSITION OF LIME-SULPHUR ANIMAL DIPS. 11 



the reaction between lime and sulphur. To the writer it appears 

 logical to believe that in a boiling solution containing both lime and 

 sulphur, that is, an unfinished solution like Preparation Q, there is 

 little but pentasulphid present. If any lower polysulphid really is 

 the first product, it apparently at once takes up more sulphur and 

 becomes pentasulphid. Especially is this likely to be true from the 

 well-known fact that hot solutions can dissolve notably more sulphur 

 than corresponds to the formula CaS 5 . If the foregoing is granted, 

 then it follows that tetrasulphid present at the end has mainly re- 

 sulted from the secondary reaction of pentasulphid with lime. 



HIGHER POLYSULPHIDS; EFFECT OF OXIDATION. 



When a lime-sulphur solution is exposed to air, calcium polysul- 

 phid is oxidized to calcium thiosulphate and sulphur. It seems ra- 

 tional that in the presence of this nascent sulphur calcium polysul- 

 phid remaining undecomposed should pass to the highest possible 

 stage of sulphurization, and that data thus obtained regarding the 

 highest polysulphid of calcium existing in solution should be much 

 more trustworthy than those derived from the rather dubious method 

 of Auld 8 which led him to infer the existence of polysulphids much 

 higher than the pentasulphid. 



EXPERIMENT 11. 



A portion of a dilution prepared about two months previously from a con- 

 centrate of high lime-sulphur ratio was vigorously shaken in a flask connected 

 without exit tube with a small gasometer of pure oxygen. A considerable 

 quantity of oxygen was absorbed while the solution remained perfectly clear, 

 during which stage the nascent sulphur was evidently wholly entering combi- 

 nation to produce higher calcium polysulphids than were originally present. 

 At a certain point, however, the solution suddenly became opalescent, and 

 thereafter rapidly increased in turbidity. Treatment with oxygen, which 

 altogether occupied but a brief time, was stopped when a considerable quantity 

 of free sulphur appeared present, and the solution was transferred to a well- 

 filled and sealed bottle. Vigorous shaking coagulated the sulphur, but some 

 air had become entangled, so it was necessary the next day to filter rapidly 

 through a loose plug of cotton, after Avhich both the original solution (sample 

 R-l) and the oxidized solution (sample R-2) were analyzed. The titration 

 results are given in Table 1. 



The value of x in the M 2 S X of sample R-l was, therefore, 4.44, 

 while after oxidation the value of x in CaS x for sample R-2 rose to 

 4.99. Another experiment in which a very slow current of air was 

 bubbled for a long time gave exactly the same figure. Therefore it is 

 plain that a lime-sulphur solution as applied in practice never con- 

 tains a calcium polysulphid higher than the pentasulphid. On the 

 other hand any lower polysulphid present in the solution before appli- 

 cation probably becomes pentasulphid through free contact with air 

 soon after if not during the process of application. 



