180 
spoken of as a hardy rubber-yielding one, in spite of the French 
work, already referred to, published ten years previously. The 
writer at this period took up the investigation of the bark. 
A preliminary examination convinced him that the substance 
had not the characteristics of rubber. On the other hand 
though resembling gutta-percha, it was found to be tougher and 
less plastic on heating. 
Extraction by means of solvents is not, as a rule, to be 
recommended for rubber, gutta and such like bodies, as their 
desirable physical properties are apt to suffer in the process. 
Mechanical separation, when possible, is to be preferred. A firm 
of engineers interested in the rubber industry undertook in 1911 
to experiment with the bark. The smaller bale was delivered 
over to it and attempts were made to separate the gutta-percha 
from the Eucommia bark; but the results were not satisfactory. 
The substance could not be obtained free from particles of bark. 
With the rapid fall in the price of raw rubber from the boom 
figures of 1910, interest fell off in new sources of rubber and 
allied substances, and ager firms were no longer eager to 
experiment with unknown bark 
After the war Dr. P. Schidrowitz, to whom I am indebted 
for the information below, kindly undertook the investigation 
of the larger bale of bark and managed with some difficulty to 
separate in a clean state the gutta-like substance, which is 
tough and almost horny in consistency, and has the dark colour 
of most raw rubbers, but without their elasticity It is quite 
free from stickiness. By mechanical extraction the bark yields 
about two per cent.; whereas that of ordinary gutta trees gives 
twice or thrice this quantity. 
The composition of this material is approximately as 
follows :— 
Moisture - - : : - 5-0 per cent. 
Ash - - - - ee te i; 
Resin - - - - - - 70-0 . 
** Gutta-percha”’ - - - - 22°65 ‘ 
i.e., hydrocarbon (C,,H,,)x 
It thus has a higher percentage of resin and a lower per- 
centage of (C, H,,)x hydrocarbon than the raw gutta-percha 
of commerce, obtained from sapotaceous trees. 
As regards its physical properties and economic DP cpomee 
Dr_ Schidrowitz wrote to me in March, 1920, as follow 
decidedly ‘short’ and does not compare af Fee with 
‘ hardened ’ (1.e., extracted) gutta-percha. The electrical (insula- 
tion) properties are probably similar to certain grades of gutta, 
but so far as ‘ageing’ goes, the indications are that it does 
uot compare favourably with good gutta. Of course, at a really 
low price (say 1/— to 1/6 per lb.) a use might be found for it, 
but I gather that miter: of that kind is out of the question. 
