Aug. 18,1923 
Sulphur Compounds in Dry Lime-Sulphur 
325 
Taking into consideration the above statements, it is believed to be 
impossible to make accurate comparisons, based on solutions, between 
different brands of lime-sulphur products when the products so compared 
are of varying composition. Therefore accurate results can be obtained 
only by the application of methods directly to the lime-sulphur powder 
and not to a diluted portion of a highly concentrated solution. 
For the determination of thiosulphate sulphur all investigators accept 
the method used—namely, the titration of the filtrate after the removal 
of the free sulphur and sulphid, by the use of a standard iodin solution. 
The procedure followed in obtaining the thiosulphate solution, however, 
varies, and the results for thiosulphate sulphur are more or less influenced 
according to the method employed for the separation of polysulphid 
sulphur from the thiosulphate solution. 
The determination of total sulphur is essentially alike in all cases, 
the total sulphur in solution being oxidized to sulphate either by the use 
of H 2 0 2 or Na 2 0 2 , and determined as BaS 0 4 . 
The important differences between the various methods described are 
in the determination of the monosulphid and the so-called polysulphid 
sulphur. The determination of the former by the use of an N/10 ammo* 
niacal solution of ZnCl 2 with NiS 0 4 as an outside indicator is considered, 
theoretically at least, as being sound, but the difficulty experienced in 
obtaining pure zinc and the laborious method of procedure in the use of 
an outside indicator would make such a method secondary to any other 
method whose accuracy could be relied upon. 
The inaccuracy in the estimation of monosulphid sulphur by standard 
iodin solution is due largely to the fact that hydrolysis of the calcium 
polysulphid occurs, and in consequence the iodin reacts also with the 
base formed, giving too high a value for the monosulphid sulphur. 
The same criticisms may be applied to the iodin method as modified by 
Averitt. Though the sensitiveness of sodium nitroprussid is reduced 
when it is used with iodin as an inside indicator, this use differentiates 
an end-point more clearly by the production of color than does the use of 
iodin alone by the destruction of the color of sulphids in solution. 
The end-point for the thiosulphate determination is unsatisfactory, 
with or without starch, because of the instability in the color developed 
by the addition of iodin. 
The use of N/2 HC 1 is preferable to N/10 HC 1 for the titration of the 
sulphid solution, since the end-point with methyl orange is much sharper. 
The titration with HC1 can be so conducted as to result in no appreciable 
action upon the thiosulphate in solution. The inaccuracy, resulting 
from calculating the amount of sulphid sulphur present from the num¬ 
ber of cubic centimeters of HC 1 used, is believed to be due to the fact 
that the amount of HC1 required is more nearly a measure of almost the 
total amount of calcium present in the solution. 
The methods in which metallic salt solutions are employed for the 
determination of the polysulphid sulphur produce colloidal substances 
and the chemist is confronted with the difficulties of adsorption, slowness 
of filtering, and possible oxidation of sulphid. 
DESCRIPTION OF PROPOSED METHODS 
method A 
In this method the solutions used were: Hydrated sodium peroxid; 
barium chlorid solution, 1 to 10; N/20 iodin; and starch. 
