PREPARATION OF RUBBER* 
By P. J. Burgess. 
The Committee of the Agri-Horticultural Show held in Kuala 
Lumpur early in August, 1904, invited me through the Government 
of the Straits Settlements to give a lecture and demonstration on 
the chemistry and the mode of preparation of marketable rubber. 
The following account of the lecture I have written at the special 
request of the Federated Malay States Government, and in it I have 
tried to repeat as far as can be done those facts and ideas which 
were then publicly stated and which were illustrated by experiment. 
The lecture was' not written out beforehand neither were formal 
notes of it prepared and consequently 1 can, in this account of it, 
only give the substance and not the form of what at Kuala Lumpur 
was partly lecture, partly demonstration and partly discussion. 
The trees on which the attention of so many is now fixed are of 
two kinds Hevea Brasiliensis, the Para rubber tree, and Ficus 
Elastica or Rambong. Those trees I shall not describe, neither 
shall I discuss the mode of extraction of the “ latex” from the tree, 
but suppose that the latex has been extracted and is now ready to 
be examined. 
In appearance it is a white or pale yellow milky liquid — its 
odour is pleasing and faintly aromatic, and if tasted it is found to 
be slightly sweet. In reaction it is, when fresh and pure, the re- 
verse of acid, that is to say, slightly alkaline. If greatly magnified 
it is seen to consist of innumerable minute globules floating in a 
colourless clear liquid. The globules are in size comparable to 
bacteria, and though passing freely through ordinary filters can be 
separated by means of Pasteur Chamberlain filter tubes. 
These globules consist of rubber mixed with a small but variable 
percentage of oils and resins, the nature of which has not yet been 
worked out. 
The liquid in which they are suspended is water carrying in 
solution some gum, sugar, mineral salts aud proteid or nitro- 
genous matter. 
Some of this liquid was prepared by filtering the latex and shewn 
during the lecture. This liquid when filtered from fresh latex 
shews an alkaline reaction; if an acid such as acetic acid be 
added a chemical reaction takes place and the proteid is thrown 
out of solution, appearing as a fine precipitate, at first barely visible 
as a faint opalescence but which finally settles out and sinks, leav- 
ing the clear liquid above. 
This reaction gives the key to the explanation of the coagulation 
of the latex on the addition of acid, a method very generally 
practised by rubber growers. The rubber globules in suspension 
in the original latex do not interfere with the proteid precipitation 
which occurs on the addition of acid, but they are caught and 
