25e; 
^^OTBS. 
Preparation of the Sample. — The total weight was taken, and about 
half of each sample, after exact weighing, was reduced to a thin 
uniform sheet under a stream of water in the usual machine employed 
for the purpose in the rubber industry. The film thus obtained was 
dried in a dark chamber at 30-35° C. and weighed, (Specimens may 
be seen in the Peradeniya Museum.) These films were then used for 
the further analyses. 
Estimation of Moisture. grammes of the film were weighed 
between tared watch-glasses and dried for 6 hours at 60° C., after 
which the weight is constant, but when exposed to ordinary air increases 
by the 0’3-0'5 per cent, of moisture, which is normally present in 
caoutchouc. 
Estimation of Ash. — An exact weight, about 2 grm., was calcined 
in a platinum crucible, the operation being carried on very slowly until 
complete distillation of the caoutchouc, when a little ignition yields a 
perfectly white ash. 
Estimatioîi of Resins soluble in Acetone. — An exact weight of about 
2 grm. of film was extracted in a Soxhlet’s apparatus. The form used 
was a globe of about 100 cc., containing about one-half its volume of 
pure anhydrous acetone, CH3 (COOH) , The film after extraction by 
four hours’ boiling was dried in vacuo. The loss of weight, less the 
moisture-content determined by the first analysis, gives the proportion 
of resin. The figures obtained in different analyses were very con- 
sistent, as the table shows. 
Estimation of Resins soluble in Mixture of Benzine and Alcohol. — Five 
grm. of film were dissolved in 100 cc. of pure benzine and 150 cc. of 
strong alcohol (95 per cent, or stronger), then stirred in. The caout- 
chouc is precipitated as flakes, which run together into a clot ; this is 
washed several times with alcohol, and dried till the weight is constant 
on a glass or porcelain dish in a chamber kept at 30-35° C. The loss 
of weight is regarded as representing the total resin. The repetition 
of this operation gives a further loss of 0*5 to PO per cent, of the 
weight of the caoutchouc, and a third operation a further one of 
usually about 0'25 per cent. The figures given in the table are the 
result from one operation only and therefore require correction, but 
are comparable among themselves. 
We have now to consider what conclusions may be drawn from these 
analyses. 
In the first place, it is evident that the cleanliness of the rubber 
prepared by Mr. Parkin’s methods is very great. Most commercial 
Para rubbers after treatment with the machine yield only 84-90 per 
cent, of rubber, but Mr. Parkin’s give at least 98 per cent., and some 
100 per cent. Hence the rubber thus prepared should obtain, other 
things being equal, at least 10 per cent, higher price. In actual fact 
some of the rubber lately exported from Ceylon obtained 4s. 2d. per 
lb. against 3s, 96?. for best native Para, figures corresponding very 
