1922] _ WALTON—AFRICAN SORREL 165 
extracts of dried and ground material of both samples. All deter- 
minations were made at room temperature, 25°-30° C. The higher 
temperature was usually reached in the afternoon during August. 
TOTAL OXALATE 
The estimation of total oxalate was undertaken for the purpose 
of verifying the figures obtained in the acidity work, and a critical 
study of oxalate methods was not attempted. After the completion 
of this work, the writer’s attention was directed to a method, per- 
fected by W. F. Kunke, Bureau of Chemistry, for the determina- 
tion, with a high degree of accuracy, of the total oxalate content of 
plant material. Using this method on another sample of the sorrel 
foliage, KUNKE obtained materially lower figures than those reported 
in this paper for total oxalate. Because of this and the relative 
crudity of the usual method, the figures for total oxalate herein 
reported are probably somewhat high. This, however, in no way 
invalidates the data dependent on the acidity determinations (the 
figures for potassium binoxalate), as whatever error there may have 
been appears in the figures for calcium oxalate. 
The total oxalate content was estimated only on the dried and 
ground material. Two gm. was weighed into a 150 cc. volumetric 
flask, about 100 cc. of 2 per cent hydrochloric acid solution added, 
and the mixture, after being heated to boiling, was digested for 
thirty minutes on the steam bath. After cooling and completing 
the volume to 150 cc. with distilled water and mixing, the extract was 
filtered through dry filter paper. The total oxalate in roo cc. of 
the hydrochloric acid extract was estimated by precipitation with 
calcium chloride and titration of the oxalate with standard solution 
of potassium permanganate, in the usual way. Contamination of 
the calcium oxalate precipitate with organic matter necessita 
double precipitation, and the final precipitate was washed with 
I per cent acetic acid solution in the cold, for further purification.® 
Two control determinations on pure sodium oxalate were conducted 
under the same conditions as those for the sorrel samples. In the 
titration, which was carried through rapidly, there appeared to be a 
9 Final gh aceegical ah calcium oxalate in acetic acid solution would be preferable 
for a material of this na 
