602 
THE TROPICAL AGEICULTURIST. [March 1, 1899. 
By <his method of coagulatirg with chemical 
reagents it is impossible to get liil of the coagiiiateil 
proteid matter, to say noihiug of the greater part of 
the water. Morellet's' remark ilmt "le procetle 
Strauss esc ingenieiix, mais les re^ullats deson ap- 
plication sont mauvais'' may well beapjilied to ail 
these chemical methods, and the soonei tiie i^earch 
for coagulating agents is aliandried the better. 
The only other American rubber of importance, 
at present, is yielded by Caslilloa clastica. It 
appears on the market in a number of diflerent 
forms under the names of Mexican, Nicaraguan, &c. 
As far as we know C. elastka is the only species of 
the genus yielding rubber, for the 6'. Murkhaiiiia of 
Collins turns out to be n PcnOca sjrecics.t 
The latex is obtained in a roujili and ready 
fashion by hacking a spiral channel fiom tlie 
crown of the tree to the ground, or by making 
great gashes with a machete. 
Collins+ has reiominei.ded a tiiirher scoring knife 
for tapiiiiig, and since then most writers liave 
followed his had. On exiierimenting with one, 
I found it was |iracticall.v useless, as little latex 
exHiled, possibly owin;.' to I be clnsureof the ve-t-els 
by the drag of its edge, Siahhing with a broad- 
bladed knife, or with a dii-ed, as practised in 
Ceylon, § gives good results without much damage 
to the tree. I n i he previously -mentioned article 
in the " Trinidad Bulletin " (1S48), there is some 
slight confusion as to the localities suitalde for 
the growth of CaUilloa. In one place (p. 122), 
"it will scarcely i hrive in i egi'us that aie not 
equally suited to llevea sjq)," which (p. 13ii) grow 
'•on land wh ch is |)i rindically inundated, even 
to a depth of five feet." Then .p. 121), "the tree 
(Castilloa) avtiids mar.-hy or boggy lan<l,and mmi- 
fests a preference lor warm, dtep loam, ir sandy 
soil." The latter staetment is the correct one. 
The most general method of preparation in 
Mexico is to add an extract of the leaves and 
stem of the moon-flower {Ipomoca hona nox), and 
allowed the mixture to stand over-night. The 
floating clot which forms is then itressed to remove 
some of the water.|| As in all thsse cases of 
preparation by "wet" methods the rubber contains 
large quantities of water, it loses from twelve to 
thirty per cent, on drying. Another method is 
in use in TNicaiagua.1I The latex is mixed with 
about three parts of water, and allowed to stand 
over-night, when the rubber comes to the surface 
in particles are mixed with a fresh supply of water, 
and the process is again repeated. The particles 
are then brought into a solid mass by pressure. 
The latest account of this method is ap|iarently 
given by Hart, in an article on the "Coagu- 
lation ot Rubber."** who appears to have redis- 
covered it. I quote it in full as 1 may be mistaken. 
"After the addition of water, the mixture is 
well shaken ; the globules of rubber (having a 
lighter specific gravity than the albumenoids and 
proteids [sic] contained in the latex) will float 
quickly to the surface. It is found moreover 
that on the removal of albuiuenoid liquors from 
below the floating rubber, the globules rise much 
more quickly to the surface." 
•"Le Caoutchouc," &o., p. 75. 
+'" Le Caoutchouc," &c., p. 64. 
J Kew Bulletin," 1887, p. 13. c.f. "Trinidad Bulletin, ' 
1898, p 21. 
8 Collins, "Report on Caoutchouc. 
[p'Hoyal Botanical Gardens, Ceylon, 1898; Ser.I., 
No-4, p. 30. „ „„ ^, 
11 B?lt, •' Naturalist in NicRvagua, p. ii. Morn?, 
"Colony of British Honduras," p. 76. 
•• "Le Oaoutchouo," Ac, p. 62. "Kew Bulletin," 1887, 
xxvni., p. 16. 
The following criticism of this "creaming" proccM 
is given in " Le Caoutchouc et la Gutta Percha'': — 
"Ce mode rle pre|>aiation est bien t udimentaiie et 
ne peut fournir qu'un |>ro(luit de quaint iut^rieure, 
qui jieia s<uvent jrlus de 50%, buitour loiequ'il 
tiaicncment piepaid. '* 
Recently there has been some talk of extiactiof; 
ruldrer f/om leaves and twigs by means of sulvents, 
as has hten done in the ease of gutta-percha. 
A desciiption of tliis latter pioceKs may there- 
fore be of interest. It originated in the leniallneM 
of the yield of the Isonnudra gvtta trees, a 
tree from 25 to 3 years old, only giving 13 lb*, 
of gutta percha w hen felled. 1 he explanation of 
this fa' I is to be found in the work of De Ilary,t 
who showed that the lalieiferous system of the 
tree con.sisted of short, closed sacs. Tliis beinc 
the case, a creat many would remain unopened, 
arid thus a considerable per centage of the gutta- 
jiercha w<juld remain in the bark. As the demand 
for gutta-percha has been large, and the supply has 
been obtained by felling the trees, they have 
become almost extinct. J 
fcSerullas proposes to utilise the leaves and twijf* 
of the shoots frc^m the old butts to extrac the 
gum from. They are dried, treated with caustic 
jiotas-h to destory colouring matters, and treated 
with a solvent for gntta-perclia. The stdvent is 
then distilhd oil' and may be used again and again. 
Jiather more than 1 lb. of gutta percha is said 
to be yielded by 30 lbs. of chopped up fresh leaves 
and twigs. § 
For several rea.sons I do not think this prneeM 
could profitaldy be applied to the prepaiation of 
ruhlier. The n:ost important of these are (1) on 
gathering the leavrs and twigs there would be an 
immense loss fif latex, and (2) stripping trees of 
their foliage (the jiart which builds up their food 
6up)>ly) iirvariably kills them. 
The direction in which research work should 
tend, 1 venture to think, is to prepare rubber free 
from the other const it uents of latex, so that 
among ot her things, fi eight and customs charges on 
these impurities may be avoided. 
Now it has been shown conclusively that the 
chemical constitution of latex varies with its 
source, so that it is improbable that any one 
reagent can be found capable of coagulating any 
given latex. Thus from the fact that acetic acid 
coagulates the latex of certain Hevea species, it 
cannot be argued that it will coagulate the latex 
of a Kicksia species. 
Then expert o|)inions, as we have seen, show 
that the preparaiion of rubber by the«e chemical 
means is not satisfactory, for the product is tar 
fri ni pure. 
I have recently succeeded, however, in preparing 
pure rubber liy a physical process, and so demon- 
strated that chemical methods are not necessary. 
This is effected by centrifugalizing the latex in 
a special form of separating machine, when the 
rubber particles, which have a smaller specific 
gravity than the medium in which they are 
suspended, are thrown out of the bowl in an 
almost dry state They may then he converted 
into a solid mass by slignt ])ressure, or by draining 
off the small quantity of water which remains 
with a porous tile. So prepared, the rubber 
forms a translucent mass, free from its usual 
smell and from all danger of decomposition. 
• " Trinidad Bulletin." 1898, p. 131. 
t " Le Caoutchouc " &c , p. 62 
I " Comp. Anrt. Phan. and Ferns,'' p. 151. 
g SeruUas, "Kew Bulletin," 18U1, ccxiii., p. 230. 
II Kew Bulletin," ccxiv,, p, 231, 
