254 
NOTES. 
tree, thus avoiding any running of milk down the bark and consequent 
contamination. The milk is all brought into the factory and filtered 
to get rid of dirt, then mixed with the calculated quantity of acid and 
creosote, and placed in round flat dishes about 1| inch deep. In the course 
of a few hours the clot of rubber forms, and as soon as firm enough for 
lifting is taken out, washed, and rolled under heavy pressure to get as 
much water out of it as is possible. The white or pale yellow biscuit 
is then placed in a warm, but not hot, dry place, and in a few days is 
ready for market, forming a thin pale yellowish-brown biscuit, not 
unlike a sheet of gelatine. Such rubber is cleaner and tougher than 
the Para native rubber, and fetches higher prices on the market. It 
retains its good quality for several years, whereas the old shell rubber 
becomes more or less rotten if kept in Ceylon for two or three years. 
The process of clotting is quickened if the milk be heated before the 
addition of acid, almost to the boiling point ; this method also enables 
even more dirt to be removed, for the finest particles which have passed 
the filter (an ordinary fine metal sieve) float to the top as a scum 
during the heating and can be skimmed off. Comparison of the 
analyses below will show the difference between the samples obtained 
in these two ways. 
Another method of clotting and rendering antiseptic, which gives a 
very good result, is by treatment of the latex with the calculated 
quantity of mercuric chloride (corrosive sublimate). No creosote need 
be added. The milk clots in fine particles, which float to the top and 
form a cream, which is washed and poured out on a slab to dry into a 
thin sheet. 
The latex of Castilloa, as is well known, forms a cream of caoutchouc 
if simply left to stand, and on this fact is based the centrifugalization 
method of preparation, which yields such excellent rubber. Mr. Parkin 
employed for the preparation of the samples, whose analysis is given 
below, simply the method of creaming. The rubber latex being placed 
in a tall revolving cylinder with a tap at the foot was allowed to cream 
and the dirty fluid run off by the tap. Water was added and the milk 
again churned, creamed, and the water run off, and so on for three or 
four times till the rubber appeared as a nearly pure white cream 
which was then spread out on a slab to dry. 
The latex of Manihot Grlaziovii was coagulated by simple heating, 
which coagulates the proteids contained in it. 
