358 REPORT OF THE CHEMIST OF THE 
in water. It probably does not appear at all in the operation 
of making the lime-sulphur wash, because it decomposes easily 
in boiling water, and would, therefore, if formed at all, be 
changed quickly into some other compound. 
The higher sulphides of calcium, especially the pentasulphide 
(CaS,;), are most conveniently formed when lime (calcium 
oxide, CaO) and water, or calcium hydroxide (CaO,H,), are 
boiled with an excess of sulphur. By an excess of sulphur is 
meant more than enough to combine with the calcium of the 
lime compound; in the case of pure materials sulphur would 
be in excess when one uses over 100 pounds for about 44 
pounds of pure lime (calcium oxide) or 58 parts of pure slaked 
lime (calcium hydroxide). 
When the higher sulphides of calcium (CaS,;) and (CaS,) 
are formed in the preparation of the lime sulphur wash, there is 
also formed at the same time another sulphur compound, 
which is called calcium thiosulphate (CaS,O,) ; and this latter 
compound, on boiling, changes into calcium sulphite (CaSQO,) 
and free sulphur. The sulphur thus free is in condition to com- 
bine with more calcium. Calcium sulphite slowly changes into 
calcium sulphate on exposure to air. These two latter com- 
pounds, sulphite and sulphate of calcium, are not easily sol- 
uble and are therefore found in the sediment or undissolved 
portion of lime-sulphur preparations. As will be seen later, 
the most prominent sulphur compound in sediment is calcium 
sulphite (CaSO,). 
It may be stated, in addition, that compounds like calcium 
pentasulphide (CaS,) absorb oxygen on exposure to air and 
slowly change into calcium thiosulphate (CaS,0,) and free 
sulphur. In order to prevent exposure to air and avoid this 
change, the wash, unless it is to be used soon, should be stored 
in full barrels, tightly stoppered as soon as prepared. 
Briefly reviewing the preceding statements, we have seen that 
we have to deal with three kinds of sulphur compounds in con- 
nection with the lime-sulphur wash: (1) Sulphides of calcium, 
chiefly pentasulphide (CaS,;) and tetrasulphide (CaS,); (2) 
