334 
Journal of Agricultural Research 
Vol. XXV, No. 7 
Iodin solutions used as an absorbent in the determination of the mono¬ 
sulphid sulphur must be very dilute as the tendency for the precipitated 
sulphur to oxidize increases with increase in concentration. Occlusion of 
iodin by the sulphur and the volatilization of iodin, due to the passage 
of the gas through the solution, were found also to increase with increased 
concentration of the iodin solution. Good results were obtained, how¬ 
ever, in a few determinations (Table III) by the use of a weak iodin solu¬ 
tion N/20 or less, containing an appreciable quantity of acetic acid and 
a large amount of potassium iodid. Starch solution in the train following 
the iodin solution showed no volatilization of iodin. The determination 
of sulphur by weighing was in agreement with the estimation made by 
titrating the excess of iodin. On the average the use of an iodin solution 
as a means of determining the monosulphid sulphur was found unreliable. 
There is no gain in accuracy in the use of pure alkali solutions as 
absorptive agents over that obtained by the employment of a hydrated 
sodium peroxid solution (Tables II and III). The operation is somewhat 
lengthened for the reason that after the absorption the sulphur must be 
oxidized. The oxidation is best accomplished by the use of sodium 
peroxid which can easily be obtained free from sulphates. 
In the opinion of the writer it is advantageous, as well as accurate, to 
make use of a solution which answers the purpose of an absorptive and 
oxidizing solution at the same time. 
RESULTS FOR TOTAL SULPHUR 
COMPARISON BETWEEN THE CARBONIC ACID METHOD AND METHOD OF 
DIRECT OXIDATION 
The total sulphur was determined by direct oxidation with Na^CX*. 
To 0.25 or 0.5 gm. of dry lime-sulphur were added 50 to 100 cc. of freshly 
boiled and cooled distilled water. Hydrated Na^Og, or the dehydrated 
form, was then added in small amounts until the oxidation was completed, 
the flask being kept stoppered. The procedure which followed was 
the same as that used in determining the monosulphid sulphur. A 
comparison of the total sulphur determined in this way with that obtained 
by the summation of the three forms as determined by the carbonic 
acid method (average of results given in Tables II and III) is given below. 
Total sulphur. 
. 61.62 per cent. 
50.64 per cent. 
2.70 per cent 
8.36 per cent 
-61.70 per cent 
HYDROLYTIC ACTION RESULTING FROM AQUEOUS SOLUTIONS OF 
LIME-SULPHUR COMPOUNDS. 
Figure 2 is illustrative of the hydrolysis of lime-sulphur compounds 
in aqueous solutions and is therefore indicative of errors which may 
arise when the analysis of dry lime-sulphur is based on diluted portions 
of concentrated aqueous solutions. 
The experiments were conducted as follows: 
The different amounts of dry lime-sulphur were taken and transferred 
to a 500 cc. Erlenmeyer flask 6 and freshly boiled distilled water cooled 
Direct oxidation. 
H 2 C 0 3 method 
Residual sulphur. 
Thiosulphate sulphur. 
Monosulphid sulphur. 
® The same flask was used for each experiment. 
