374 REporRT OF THE CHEMIST OF THE 
TABLE X.— PERCENTAGE OF SULPHUR USEp CONVERTED INTO SOLUBLE 
SULPHIDES. 
Average percentage 

’ of sulphur Ratio of 
No. of experiments. Formula used converted calcium to 
into soluble sulphide sulphur 
Sulphur. Lime. sulphides. 
Lbs. Lbs. = Perch. Ca” AS 
1—a—1-b—1-c i eds 52 71.0 Le 2.30) 
2-—a—2-—b—2-c 4 60 82.7 1 ee 
3-—a—3-—b—3-c rs 65 85.6 1 see 
13—14—15 % 52 ba 0 I eRe) 48, 
16—17—18 ss 16 65.0 f Wins 9a Bi 825° 

From a study of the three tables preceding (VIII, LX and 
X), we notice the following points: 
(1) The preparations represented by numbers 13-15 are 
shown to contain the smallest amount of sulphide sulphur in 
proportion to the amount of sulphur used in making the mix- 
ture. The same proportions of sulphur and lime were used in 
these experiments as in 1—a—b—c. The difference is due largely 
to the presence of magnesium oxide in the commercial lime 
used in preparations 13-15, the lime used in the other work 
being strictly pure. Experiments 16-18 show less soluble sul- 
phide in proportion to sulphur used than we should expect, 
due probably to the presence of magnesium oxide in the lime 
used. 
(2) When we compare the results of the various experiments 
with reference to the ratio of calcium to sulphur, we find that 
in preparations 13-15 the sulphide appears to be tetrasulphide 
of calcium (CaS,). In preparations 16-18, the ratio of sul- 
phur to calcium is abnormally low, indicating the presence of 
calcium disulphide (CaS,) for the most part and little or no 
sulphide containing more sulphur. While this condition can 
not be authoritatively explained on the basis of any work done 
by us, it is suggested that in using lime containing magnesium 
oxide with so large an amount of water, the higher polysul- 
phides (CaS, and CaS,) were decomposed and the disulphide 
(CaS.) formed, together with free sulphur. 
(3) In comparing preparations 13-15 and 16-18, it must be 
kept in mind that the former are concentrated and before being 
