654 
tHE TEOPICAL 
AGRICULTURIST. [April 1, 1904. 
tained with Hevea latex are excellent ; those obtained 
with Castilloa latex are much less satisfactory. The 
reason for this, of course, is to be found in the fact 
that the latex of Castilloa contains about three times 
as much albumen as that of Hevea, and therefore 
produces in this treatment a 'much more impure 
rubber than the latter. It is also worth mentioning 
that rubber coagulated by means of tannic acid and, 
while still wet, placed in an incubator at temper- 
atures from 100 deg. F. upwards, rapidly passes into 
a state of putrescid fermentation, but such a change 
does not occur if the rubber is submitted to this 
test in a thoroughly dry condition. 
FCBMIC AND ACETIC ACIDS. 
The action of formic acid and of acetic acid is 
about the same, but not so energetic as that of 
tannic acid. Formic acid, weight for weight, is rather 
more expensive than acetic acid, but this is fully 
counteibalanoed by the fact that three parts of 
formic acid are quite sufficient to produce the 
same effect as four parts of acetic acid.* Formic 
acid offers, moreover, the further advantage that 
it possesses not very strong but distinct antispetic 
properties. Whichever of these two acids may be 
employed, no more of it fhould be added to the 
latex than what is just sufficient to produce coagu- 
lation. Better results are obtained in this way, 
which is also the more economical. 
The minimnm quantity of either of these two acids 
for the compleie and rapid coagulation of the latex 
varies, of course, considerably according to the per- 
centage of albumen contained in the latex, and it is 
also influenced by the nature of the albumen con- 
tained in it. For this reason it is impossible to name 
any fixed proportions applicable to all kinds of latex. 
AMOUNT OF ACID BEQUIEBD. 
I have so far not had an opportunity of determining 
the amount of albumen contained in the latex of 
Hevea raised in the East. The latex of Hevea (brasi- 
liensis) in its native habitat contains only about 1'5 per 
cent, of albumen and one-third of an ounce of anhy- 
drous formic, or one-half ounce of glacial acetic acid 
per gallon of the latex is quite sufficient to produce 
a rapid and complete coagulation. In the case of 
Castilloa latex these quantities require almost ex- 
actly doubling. In any case, the amount of full 
strecgth acid to be used for coagulation, as above 
stated, should for use be diluted with at least one 
pint of water. This solution is then added to the 
latex, the latter well stirred and allowed to stand. 
As soon as coagulation sets in, the whole is well agi- 
tated until the rubber separates out. 
WASHING THE RUBBEB, 
The coagulated rubber should be at once drained 
under cover (avoid direct sunlight), and I strongly re- 
commend to subject it to a thorough washing upon 
the same kind of rubber-washing machines as is used 
in rubber factories. These machines can easily be 
obtained in such dimensions that their transporta- 
tion in any locality offers no serious difficulties. It 
is advisable to use as motive power an oil motor 
of about 4 h.-p., and to drive the washer by means 
of a very short piece of shafting direct from the 
orank shaft of the engine. Aa an engine of the 
kind named nakea about 180 revolutions a minnte, 
the wheel gear of the machine mast be epeoially 
adapted to this speed of the driving shaft, as these 
machinei for ordinary factory purposes are geared 
for a much lower speed of the driving shaft. 
In rubber districts a kind of washing machine 
tsaembling somewhat a powerful wringing machine 
has frequently been need. This sort of machine 
offal's the advantage of greater lightDCss, but is a most 
intfflcient makeshift which should be carefully avoided) 
tts it produces results very greatly inferior to those 
obtainable with a rubber washing machine of the 
* This reiers respestivel;^ to auh^droua formic and 
glauinl acetic acidt 
normal type. This is due to the fact that the washin 
of the rubber upon a sufficiently powerful maobin 
has the effect of not only freeing it from all mother 
liquor and soluble impurities, but also to produce a 
rubber of much tougher structure. Upon the lighter 
machioes the first effect is only approximately attain- 
able, the latter not at all. 
DRYING EUBBER AFTEE WASHING. 
After the washing operation the rubber should be 
thoroughly dried in dark but well-aired sheds. The 
dry sheets, rolled up tight, should be packed in cases, 
and it is desirable that the inner side of the boards 
of these should be well planed to prevent splinters 
attaching themselves to the rubber. 
Coagulation of the latex may also be accomplished 
by means of phenol, which acts very energetically. 
As a matter of fact, however, there is no advantage 
to be gained by the use of this coagulant, and there- 
fore I do not propose to discuss it any further. But 
it may not be undesirable to, briefly survey the question 
of coagulation by smoking. As is well known, this 
is the process practised in the Amazon district 
furnishing the Para rubber, and there are still those 
who entertain the notion that the excellence of this 
rubber grade is essentially due to this exceptional 
method of preparing it. This, as I have repeatedly 
shown, is a pure superstition upheld, as superstitions 
always are, by ignorance. 
INFLUENCE OP THE AGE OP THE 
TREE ON THE QUALITY OP 
RUBBER PRODUCED. 
Samples of rubber were prepared in connection with 
the experimental cultivation of various rubber yield- 
ing trees in Trinidad, and were forwarded to the 
Scientific and Technical Department of the Imperial 
Institute chiefly with the object of ascertaining by 
chemical investigation, supplemented by commercial 
valuation, the influence of the age of the tree on 
the quality of the rubber it furnishes, and also by 
the same means to determine the effect of the 
method of coagulation employed on the quality of 
the rubber furnished by the latex. 
CASTILLOA RUBBER, 
Two small samples of rubber, prepared respectively 
from old and young trees of Castilloa elasiica, were 
forwarded to the Imperial Institute for comparative 
chemical examination by the Superintendent of the 
Iloyal Botanic Gardens, Trinidad. In the accom- 
panying letter, Mr. Hart stated that the rubber 
had been prepared from the latex by creaming and 
draining, and pointed out that in physical proper- 
ties the rubber derived from young trees was much 
inferior to that yielded by the older trees of the same 
species. 
(1 ) Rubber from young trees (4 years old). 
The specimen showed very little resemblance to 
true rubber, and was evidently highly resinous. It 
was almost black, rather hard in the lump, bat 
could be moulded by pressure, and was easily indented 
with the finger nail ; small fragments were soft and 
sticky- It exhibited very little tenacity and no 
elasticity. 
(2 ) Bnbber from old trees. 
This was a specimen of good rubber, almost black, 
only slightly sticky, very elastic and exhibiting oon< 
siderable tenacity. A chemical examination of each 
of the two epeoimeua gave the following resalts 
■ i I- 
S O fl^ <^ 
feubber from yottng trees 
(1 years old) 0 54 33 6 64-1 1-7 0*35 
Bubberfrom old trees .. 0 41 81'9 .36 S H «-3.i 
