332 
Journal of Agricultural Research 
Vol. XXV, No. 7 
The ZnS mixture upon the filter paper was transferred, by washing, 
into the reaction flask, A, air was removed from the apparatus by the 
use of N, HC 1 in excess added to decompose the carbonate and sulphid, 
and the gases evolved were expelled by the further use of N. The 
monosulphid sulphur was determined in the usual way, by oxidation to 
sulphate and weighing as BaS 0 4 , and was found to be equivalent to 8.41 
per cent. 
The employment of ZnC 0 3 in water suspension as a means of separa¬ 
tion of the sulphid from the thiosulphate was chosen because of the rapid 
rate of reaction between the ZnC 0 3 and the soluble sulphid, the readiness 
with which filtration could be accomplished, and, furthermore, for the 
reason that constant results for thiosulphate sulphur were found not to 
be dependent upon the length of time of contact between the ZnC 0 3 ahd 
the soluble sulphur compounds, as was the case when CdC 0 3 was used. 
ACTION OF CARBONIC ACID UPON CALCIUM POLYSULPHID 
The power of carbonic acid to decompose water soluble sulphids can 
be easily demonstrated by the passage of carbon dioxid into an aqueous 
solution of lime-sulphur compounds. The completeness of the reaction 
can be positively verified by testing the solution in which the sulphid 
was dissolved by the introduction of sodium nitroprussid, after the 
carbonic acid has been allowed to react for a sufficient length of time. 
The time necessary for the complete decomposition of polysulphid is 
very short, as indicated by the disappearance of the yellow color of the 
polysulphid in solution. Complete decomposition was effected, repeat¬ 
edly, within from two to three minutes, when 0.25 gm. charges were used. 
In the case of larger charges the time was naturally lengthened, requir¬ 
ing from three to four minutes with charges as large as 0.5 gm. The 
time is based upon the passage of carbon dioxid at a moderate rate. In 
Table II are tabulated results expressing the quantitative reaction 
between carbonic acid and lime-sulphur compounds. 
EFFECT OF CARBONIC ACID UPON THIOSULPHATE 
Investigators of lime-sulphur solutions who have made use of HC 1 in 
the process of analysis claim that the neutralization of the solution can 
be brought about by the careful addition of N/20 acid, in the presence of 
methyl orange or methyl red as indicator, without its reacting upon the 
thiosulphate. If a highly ionized acid, such as HCl, can be so used with¬ 
out destroying any of the thiosulphate, then the chances of a destructive 
action occurring with the use of an acid which is ionized to a much less 
degree should be, theoretically at least, even less. 
In corroboration of this reasoning, experiments were conducted for 
the purpose of ascertaining whether or not the action of carbonic acid 
for different lengths of time had any appreciable effect upon the thio¬ 
sulphate. The results given in Table II indicate that the weakly ionized 
acid does not react with the thiosulphate. The occurrence of the ob¬ 
served slight differences in the amounts of thiosulphate sulphur may be 
due to slight variations in the homogeneity of the lime-sulphur mixtures, 
or to slight changes in the chemical constituents resulting from repeated 
openings of the bottle containing the lime-sulphur powder. The perfect 
agreement in results between a one-plus hour, and the 17%-hoxxr period 
might be assumed as conclusive proof that the concentration of hydrogen- 
ions resulting from the solution of H 2 C 0 3 is without effect upon a 
solution of calcium thiosulphate. 
