COMPOSITION OF LIME-SULPHUR ANIMAL DIPS. 9 



To eliminate the disturbing effect of hydrolysis which had evidently occurred, 

 Preparation N was made by charging 20 grams sulphur and slaked lime equiv- 

 alent to 9 grams available calcium oxid into a 4-ounce sample oil bottle, which 

 was then filled with water and sealed. For some weeks the bottle was shaken 

 by machine several hours each working day, but the action was so slow that 

 finally it was simply given a brief shaking by hand once or twice a day. After 

 42 days a sample of the clear liquid, diluted to 2 volumes, showed the molecular 

 ratio M 2 Sx : M 2 S 2 3 =1.92. 



The last preparation suffered a slight exposure to air while the necessary 

 degree of dilution for analysis was being ascertained. To get further light on 

 the possibilities Preparation O was similarly made, but using only 10 grams 

 sulphur and employing a slight calculated excess of caustic soda solution in- 

 stead of lime. In 5 clays the sulphur was entirely dissolved, and on the next 

 •day a 4-volume dilution showed the molecular ratio M 2 S* : M 2 S 2 3 =1.93. The 

 dilution had been prepared by pipetting 25 c. c. into a 100 c. c. volumetric flask 

 about half full of water, then making to the mark. The diluted solution was 

 filled into 15 c. c. glass-stoppered bottles, one of which was used for each test. 

 Freshly boiled water was used for the original preparation and for the dilution. 



From Experiment 8 it is evident that the fundamental reaction 

 hetween lime and sulphur is parallel to that between caustic soda and 

 sulphur and it must be assumed that two molecules of polysulphid 

 are produced for each molecule of thiosrlphate. The analytical 

 methods are not known to be at fault except in a minute error of 

 end-point, arising from the necessity of obtaining the sulphid-acid 

 figure by subtraction. The chief cause of the failure to reach the 

 theoretical ratio must, therefore, be oxidation during the manipu- 

 lation of the solutions. An oxidation of 1 per cent of the mono- 

 sulphur to thiosulphate by calculation would produce a drop in the 

 ratio from 2.00 to 1.94. 



LOWER POLYSULPHIDS; EFFECT OF EXCESS OF LIME. 



The composition of the crystalline polysulphid which sometimes 

 forms in a solution prepared with excessive lime has received consid- 

 erable previous study with conflicting results. 8 It seems, however, to 

 have been proved to be a basic polysulphid which is decomposed 

 when treated with water into calcium hydrate and a soluble calcium 

 polysulphid that was first stated by Schone to be tetrasulphid. For 

 present study the composition of the crystals themselves is imma- 

 terial, since we are only concerned with polysulphids in solution. 

 So far as work subsequent to Schone has covered the question it has 

 only served to confirm his observations and to strengthen the hy- 

 pothesis that tetrasulphid is the lowest polysulphid ever occurring 

 in a lime-sulphur solution. Only the following experiment was, 

 therefore, thought necessary. 



EXPERIMENT 9. 



Preparation P, originally intended to follow Preparation E in Experiment 

 3, was made on the formula 70 : 100 : 521, boiling for one hour. After standing 



