1922] EATON—SULPHUR CONTENT OF SOILS 35 
Methods 
Three methods of total sulphur determination were tested, the 
sodium peroxide method as evolved by Hart and Peterson (8), the 
VAN BEMMELEN method as modified by the same investigators, and 
a sodium carbonate fusion method, which was really a combination 
of Kocn’s (12) sodium carbonate method for the determination of 
total sulphur in organic material and HILLEBRAND’s (10) sodium 
carbonate method for the determination of total sulphur in rocks. 
The sodium peroxide method gave as high results as the other 
methods and better duplicates, and also was easier to manipulate. 
It was therefore adopted, but modified somewhat, and so it is 
given in some detail. 
Ten grams of soil was placed in a roo cc. nickel crucible, made 
quite moist with water, and 1o gm. of sodium peroxide added, 
a little at a time, stirring thoroughly with a nickel rod as the 
sodium peroxide was being added. This was heated slowly with 
a microburner until dry, and 10 gm. more of sodium peroxide 
added, spreading it over the surface, and continuing the heating 
until the surface layer melted. With a blast burner the mass 
was then brought to red heat and kept in this condition for ten 
minutes, stirring thoroughly. This was allowed to stand over a 
moderate flame for one hour, cooled, and the fused mass removed 
with boiling water, transferring it to a 600 cc. beaker. This was 
neutralized with concentrated HCl and then 10 cc. excess added, 
and allowed to stand on the steam bath for five or six hours, or 
until there was no undecomposed material in the bottom. It 
was next transferred to a 5oocc. volumetric flask, cooled, filled 
to the mark, and allowed to stand for four or five hours, shaking 
at intervals. A 250 cc. aliquot was filtered off, transferred to a 
beaker, a quantity of filter paper pulp added, and while stirring 
the iron, aluminum, etc., was precipitated out with ammonium 
hydroxide. This was heated for an hour on the steam bath, 
filtered into an 800 cc. beaker, and the precipitate washed with 
hot water until 600 cc. was obtained. After this it was heated to 
boiling, to cc. of hot 10 per cent barium chloride added to the 
boiling solution, and allowed to stand on the steam bath over 
night and at room temperature for the remainder of the twenty- 
