to render its continued employment most deplorable. The coagula- 
tion with' soap as practised in the Isthmus of Panama is barbarous 
in the extreme, and it is not surprising that it yields a product of 
very bad quality indeed. 
Amongst the above-named process I have not enumerated a pro- 
cess said to be practised in Mexico, and simply consisting in the 
boiling of the latex in earthen vessels (jacaras). If this process is 
actually used, it can certainly not be carried out with the fresh latex 
for the simple reason that over and over again 1 have satisfied my- 
self that even on very prolonged boiling of the slightly diluted latex 
furnished by the tree at Las Cascadas no coagulation can be ob- 
tained. The cause of this is to be found in the fact that the aqueous 
vehicle of the latex, although it certainly contains a large amount of 
albuminous matter when rapidly separated from the latex immedi- 
ately after this has been obtained, is of a very light olive green 
colour and even on very prolonged boiling does not coagulate, nor 
even become turbid. On standing exposed to the air this aqueous 
vehicle very rapidly assumes a darker colour, and eventually forms 
an almost inky liquid. This, on boiling, undergoes immediate coagula- 
tion, and a most copious deposit of insoluble albumen is obtained. 
In entire agreement with this observation is the fact that if the 
Castilloa latex be allowed to stand for sometime until it has assumed 
a very dark colour it will now be found that on short boiling rapid 
and complete coagulation takes place. I have not yet succeeded 
in ascertaining the cause of this curious phenomenon, but it is ob- 
vious that unless the Castilloa latex obtained in Mexico differs very 
considerably from the latex yielded by the same trees in the Isthmus 
coagulation by boiling in Mexico, must be preceded by an ageing 
of the latex as otherwise no coagulation would take place. 
ft is not very easy to see that the chief point in attempting to 
prepare a pure rubber from the latex of Castilloa elastica, and as a 
matter of fact, from the latex of any other rubber tree, must consist 
in the elimination from the rubber, prior to its “ agglutination, ” of 
all albuminous matter. The first step in this direction is the dilut- 
ing of the crude latex with water, of which at least five times the 
volume of the latex treated should be used. In the case of the 
thick, curdy latex yielded by the trees at Las Cascadas it is prefer- 
able to use actually boiling water, but in how far this applies to the 
latex obtained in other districts or from different trees is a matter 
for experiment. Boiling water at once converts this latex into a 
thin, very fluid milk which through a common cotton gauze is strained 
in order to remove from it any insoluble impurities such as earth, 
wood, bark, and the like. This milk is best strained into thorough- 
ly well washed petroleum barrels. As soon as the barrel is com- 
pletely filled, about 8 ozs. of formaldehyde are added, the whole 
well stirred, and allowed to stand for 24 hours. The action of the 
formaldehyde appears to be twofold. In the first instance, it 
effectually prevents any tendency of the albumen to coagulate in 
the hot solution, and thereby to cause mischief. But, as compara- 
tive experiments showed beyond any doubt, it also has a most 
distinct effect upon the india- rubber, which collects on the top of 
