19 
Shaking or churning has proved useless and the usual coagulants 
have failed to produce coagulation. 
The method I have devised is as follows : — 
The latex is warmed to 40® C and a solution of tannic acid of 
known strength is prepared, the solution 1 used being of 2 per cent 
strength. This solution is added to the latex until there is one per 
cent of tannic acid'present in the latex. In the case of a two psrcent 
solution of tannic add this will naturally mean the addition of the 
solution in the proportion of one to 19. The mixture is then gently 
beaten or churned. Violent agitation leading to the formation of 
froth should be avoided while simple shaking or stirring is not very 
efficient. 
In one or two minutes the whole mass sets to a cream which on 
gentle agitation becomes quite coherent and which then may be 
lifted out by hand, rolled or washed on a washing machine. The 
coagulation is complete, the liquid remaining being clean or at most 
faintly opalescent. 
This method is quite successful with natural latex, but if the latex 
be diluted w«th water the process is more difficult to carry out and 
more of the tannic acid solution is necessary. 
Tannic acid is not corrosive. It is bought in the solid state and the 
price in London is 2/- a pound. One pound of acid will be sufficient 
for preparation of 300 to 400 pounds of dry rubber. 
This process as described I believe to be quite new and it is essen- 
tially a practical process for use on rubber estates. 
P. J. BURGESS, 
Government Analyst Labor atavy. 
MISCELLANEOUS, 
Notices to Subscribers. 
1. For the information of subscribers and others who wish to 
complete their series of Bulletins, notice is given that numbers 
1, 7, 8 and 9, of the old Series (1891 to 1900) and Nos. 1, 8, 9 and 
ro, of New Series, Vol. I (1901-1902) have been reprinted and 
copies can be had by all whose subscriptions are paid up to date. 
The cost to others is 50 cents a number. 
2. A very large number of subscriptions, even for last year, are 
yet unpaid although subscribers have received more than one notice 
of the delay in payment. As this entails a good deal of extra work 
on the staff, subscribers are asked to send in their subscriptions 
without delay. Attention is called to the rule that all subscriptions 
should be prepaid. 
3. Subscribers changing their addresses are requested to give 
notice to the Editor. 
&iu 
