1922] WALTON—AFRICAN SORREL 161 
Procedure 
MOISTURE 
The bulk of the material of each sample was used for the deter- 
mination of moisture, but only entire leaves, with their petioles, 
were taken. After recording the total green weights, the midribs, 
larger veins, and petioles were split by a sharp knife to facilitate 
evaporation, and the material was rapidly dried at 65°—70° C. ina 
well ventilated oven, until friable. It was then crushed, care being 
taken to avoid loss of substance, and the samples finally dried to 
constant weight at 65°-70°C. in a vacuum oven. The loss in 
weight, about 90 per cent of the green weight, was taken to be total 
moisture. The dried material was ground and reserved for further 
study. ) 
TOTAL ACIDITY OF WATER EXTRACT 
Several sound leaves with petioles, representative of the fresh 
green material, were selected from each sample, and the weights of 
the two charges recorded. In the case of the larger foliage two 
leaves, weighing 43 gm., constituted the charge, while several leaves, 
weighing in the aggregate 25 gm., represented the sample of smaller 
foliage. Each charge was thoroughly macerated in a glass mortar, 
and the resulting pulp transferred to a four-sided glass 8 oz. sample 
jar, with exactly 200 cc. of distilled water, previously boiled and 
cooled to room temperature. After violently stirring the mixture 
for 30 minutes by means of an electric mixer,‘ it was thrown on dry 
filter paper. The first (cloudy) portion of the filtrate was rejected, 
and the total acidity in an aliquot of the clear extract was deter- 
mined by titrating with N/1o sodium hydroxide solution, using 
phenolphthalein as indicator. The presence in the water extract of 
a natural indicator,’ the strongly darkening color of which tended 
to obscure the end-point of the titration, made it necessary to carry 
through concurrently a blank with a similar aliquot of extract with- 
P 4 Described in Circular 68, Office of the Secretary, U.S. Department of Agricul- 
ure, 
5 This natural dye in the leaves of R. abyssinicus Jacq. appears pink in dilute 
aqueous extracts of natural acidity. As titration with a fixed base progresses, the 
color changes through yellow to brown, at about the neutral point, and the solution 
becomes inky when made distinctly alkaline. 
