326 
Journal of Agricultural Research 
Vol. XXV, No. 7 
The hydrated sodium peroxid is prepared by placing C. P. sodium 
peroxid under a bell jar with a separate container of water. Air is 
excluded to prevent the formation of sodium carbonate. The yellow 
color of the peroxid gradually disappears with the absorption of moisture 
and the hydrate (Na 2 0 2 8 H 2 0 ) is formed. This hydrated product can 
be dissolved in water at room temperature with but slight decomposi¬ 
tion, or in cool water with practically no decomposition at all. The 
solution of sodium peroxid may be brought to the temperature of the 
steam bath with but slight loss of oxygen, and if used at this higher 
temperature increases the rate of oxidation of the hydrogen sulphid. 
PROCEDURE 
Sufficient hydrated sodium peroxid and ioo cc. of distilled water are 
added to flasks No. i and No. 2 (fig. 1) and the flasks connected to the 
apparatus; 0.5 gm. of dry lime-sulphur is transferred to the reaction 
Fig. x.—Apparatus for the direct separation of the three forms of sulphur—namely, monosulphid, thiosul¬ 
phate and polysulphid sulphur (plus any free sulphur). The hydrogen sulphid or monosulphid sulphur 
will be in solution in flask No. i, thiosulphate sulphur in solution in flask A, and the precipitated or 
residual sulphur in flask A will consist of the polysulphid sulphur plus any free sulphur. 
flask, A. Carbon dioxid (generated by the action of hydrochloric acid 
upon marble in a Kipp generator), freed from all traces of hydrochloric 
acid and moisture by passage through a saturated solution of sodium 
bicarbonate and then through a solution of concentrated sulphuric acid, 
is forced through the apparatus to replace all air, and without shutting off 
the current of carbon dioxid, 50 to 60 cc. of distilled water are added to 
flask A by means of the separatory funnel. The reaction flask is shaken 
continuously for from three to five minutes, after which time the agitation 
is carried out intermittently until all the hydrogen sulphid has been 
expelled and absorbed in the alkaline solutions contained in flasks No. 1 
and No. 2. 
The contents of flask A are filtered, after the complete expulsion of 
all traces of hydrogen sulphid, through a platinum Gooch crucible with 
a thin asbestos pad, and the residue in the crucible is well washed and 
the filtrate made up to a volume of 200 cc. and titrated with N/20 iodin 
with starch solution as indicator. The iodin titration determines the 
thiosulphate sulphur. 
