210 TlMEHRI. 
or less deep brown colour, often with a pink tinge, is comparatively soft 
and flexible and does not wholly dissolve in bisulphide of carbon. The 
proportion of insoluble matter was determined in a sample of dried 
gum and was found to be 1289 per cent, a result which agrees fairly 
well with the estimated impurities in the juice given above. The nature 
of this foreign matter associated with the gum is still under investiga- 
tion. 
The quantity of gum present in the bark was determined as follows : 
— The bark was partially dried in the sun for a few days and then 
broken into small pieces and ground to powder in a mill. Twenty 
grammes of the powder were weighed out and dried in a hot air oven 
at ioo° C and the loss in weight, representing the amount of moisture, 
noted. The dry powder was then placed in a Soxhlet's extraction 
apparatus and thoroughly exhausted with hot bisulphide of carbon. 
The latter, containing all the gum in solution was then poured into a 
basin and allowed to evaporate spontaneously. The basin containing 
the residual gum was then placed in the air bath at ioo° C and kept 
there until it ceased to lose weight. The excess in weight over the 
empty basin of course showed the amount of gum yielded by the 20 
grammes of bark The following are the results obtained : — 
Sample 1. — Bark from part of tree that had been tapped, contained : 
Moisture 9*38 per cent., Gum 6*28 per cent., proportion of gum in dry 
bark 6*93 per cent., equal to crude gum 7*99 percent. 
Sample 2.— Bark from portion of tree that had not been tapped 
contained : Moisture 9"i9 per cent., Gum 769 per cent. Proportion of 
Gum in dry bark 8*48 per cent., equal to crude gum 978 per cent. 
Sample 3. — Bark taken from tree about a fortnight after it was felled 
contained: Moisture 10*08 per cent., Gum 970 per cent. Proportion of 
Gum in dry bark 1080 per cent., equal to crude gum 12 '46 per cent.* 
When brought in by the collectors, the milk contains 
more or less of foreign matter in the form of dirt, bits of 
moss and leaves, chips of bark, &c. Those who want to 
produce clean balata, strain this out by running the milk 
* This must have been a better sample of bark though from the same 
tree, than the two preceding, to account for the larger quantity of balata 
it contained ; for the secretion could hardly have increased after the tree 
was felled during the fortnight that had elapsed. 
