12 BULLETIN 451, U. S. DEPARTMENT OF AGRICULTURE. 
It is interesting to note the change in reaction figure between sam- 
ples R-l and R-2. The change is, of course, perfectly logical, for the 
hydrogen sulphid which produces the negative reaction figure be- 
comes simply sulphur and water upon oxidation. In deducing the 
equation to express oxidation, it is accordingly necessary in this case 
to employ the sulphid-base figures and not the sulphid-acid figiires. 
The change of sulphid-base figure from sample E-l to sample B-2 
is 28.13-15.51=12.62 loss, which, according to the accepted equation 
CaS x +30=CaS 2 0,+ (x-2)S, should be balanced by a gain of one- 
half as much, or 6.31, in the thiosulphate figure. The actual gain in 
the thiosulphate figure in the experiment was 6.24, which is in reason- 
able agreement. 
CONCLUSIONS. 
The reactions which determine the composition of lime-sulphur 
solutions, besides being rather numerous, are some of them reversible, 
the points of equilibrium varying according as the solution is hot or 
cold, dilute or concentrated, or exposed to the influence of other vary- 
ing conditions. Under such circumstances the only way in which 
laboratory studies can be of practical value is by so thoroughly estab- 
lishing the fundamental principles involved and the effect of varying 
conditions upon the relative importance of such principles as to afford 
a sound basis for reasoning. 
It appears that when lime and sulphur are boiled with water, ignor- 
ing unessential and hypothetical intermediate compounds, the follow- 
ing reactions occur : 
(1) 3Ca(OH),+12S=2CaS 5 +CaS,0 8 +3H 9 
(2) lOCaS 5 +3Ca(OH) 9 =12CaS 4 +CaS 9 3 + 3H 2 
(3) CaS 4 +S=CaS 5 
Only when substantially all free sulphur has been dissolved will 
equation 2 become operative or equation 3 fail to hold all poly- 
sulphid substantially up to the pentasulphid. 
All lime-sulphur solutions are subject to hydrolytic decomposition 
according to the equation: 
(4) CaS x +H 2 0*Ca(OH) 2 +H 2 S+ (x-1) S, 
the pressure of the reaction from left to right increasing with rise of 
temperature. "Whether or not hydrogen sulphid can escape, the 
remaining products on the right-hand side react according to equa- 
tion 1, giving as final result, in case of CaS 5 . 
(5) CaS 5 +3H 2 0=CaS 2 3 +3H 2 S. 
Thus all solutions are in equilibrium only when they contain a cer- 
tain excess of hydrogen sulphid. the amount being dependent upon 
the temperatures and concentrations of the solutions. 
