June i, 1901.] 



THE INDIA RUBBER WORLD 



265 



PREPARATION OF RUBBER. 



TO THE Editor of The India Rubber World: Having 

 read, under the heading of the " Coagulation of Latex," 

 in your issue of January i, Mr. Parkin's reply to my coniiiients 

 on his paper published in the Annals of Botany, I cannot see 

 that he seriously traverses the several points I raised in my 

 paper in The India Rubber World, October i, 1900. In the 

 first place, he admits the misuse of the word " pure," for lattw 

 as extracted from the tree, by explaining that it would be " un- 

 derstood by most readers." Per contra, he appears inconsis- 

 tent when he makes objection to my use of the word "coagu- 

 lation," as I have just as good a right to claim the understanding 

 of the " general reader " as he has himself, and moreover I had 

 anticipated the objection by pointing out a possible " confu- 

 sion " as resting with him. 



Again, Mr. Parkin makes an assertion in his reply to meet 

 the point, which does not appear to cover the case; and lor 

 which, moreover, he has presented no evidence in support. He 

 says : " In -ivhat may and to what extent the collected latex may 

 have been contaminated by the surrounding tissues, are matters of 

 conjecture only ; " and yet he admits that some of the contents 

 of the bark vessels " may find their way into the laticiferous 

 stream." The extent of the contamination is, however, fairly 

 well shown, when it can be proved that Castilloa fluids contain 

 at least 75 per cent, of matter which is not rubber, as shown by 

 Biffen. The laticiferous tissue having been found filled to dis- 

 tension with solid rubber, would also appear to prove that the 

 greater part of the fluids are drawn from other sources, and not 

 from this tissue. 



It is true that the water conducting vessels need not be in- 

 jured to obtain rubber fluids, but nevertheless they are generally 

 so wounded, and the dilution thus made must be accounted for- 

 Mr. Parkin accounts for it by offering an opinion, "that sugar 

 and proteids may come from this source," but the difference in 

 density is to be accounted for by the water contained in the 

 laticiferous tubes themselves; thus showing that he allows the 

 presence of water in the bark, while he apparently desires to 

 show that the wood vessels must be pierced to obtain it. That 

 the water which forms a part of all rubber fluids all comes from 

 the laticiferous tissue is a point, proof of which is wanting. 



Mr. Parkin further states that in his experiments " nothing 

 was suggested which tended to the conclusion that the quan- 

 tity of the coagulator required is in proportion to the amount 

 of rubber to be coagulated " and yet in his paper in the Annals 

 of Botany [p. 196] states that the quantity of acid needed " de- 

 pends on the amount of pure latex present in the liquor to be 

 clotted." How would the "general reader" understand the 

 meaning of the words " pure latex," in this sentence .' The 

 Trinidad experiments show that rubber globules can be clotted, 

 coagulated, coalesced, aggregated, fused, or massed together, 

 when washed clean of proteid matter, and when suspended in 

 water, by the addition of any medium which will rupture the 

 globule itself, and the experiment has been performed again 

 and again with unvarying success. Be the action " coagula- 

 tion " or not, in the true scientific meaning of the word, I fail 

 to see that any service can be rendered to the rubber industry 

 by discussing the relative merits of words to be used for the 

 clotting or fusing together of rubber particles, or the manner 

 of the separation of a solid substance from the liquid in which 

 it is usually suspended. 



Besides, my comments on Mr. Parkin's work were chiefly to 

 show that rubber would be better in quality, if prepared with- 

 out coagulation, as understood by Mr. Parkin ; for it is quite 

 clear, from his own statements, that the material must be purer 



when the rubber particles are massed together, fused, or coal- 

 esced, without the aid of, and independent of, proteids. Mr. 

 Biflfen in his paper uses the words " spontaneous coagulation " 

 and records having observed this action taking place when 

 latex was in contact with air : but was this " coagulation " ac- 

 cording to Mr. Parkin, or was it merely the coalescence of the 

 particles such as I record in my experiments? Oris Mr. Biflfen 

 also to be said to have used the word in a wrong sense .' The 

 fact remains that rubber globules can be clotted by alcohol 

 when washed clean of proteid matter (except what they may 

 themselves contain), and this method of binding them together 

 is that referred to as the means by which probably the purest 

 rubber could be obtained. 



Rubber globules can also be massed together by nitric acid, 

 the action of which is to completely clear the watery liquors 

 by the massing or creaming of the rubber particles on the sur- 

 face. The first washings of rubber fluids when cleared of the 

 rubber particles, by creaming or centrifugal action, can be coag- 

 ulated by acids, but the solid material is not rubber ; and has 

 nothing to lecommend it, for mixture therewith, so far as can 

 now be seen. By volume, this matter forms about .01 per cent, 

 of our fluids, but the amount probably varies in different trees 

 and in different seasons. The residual liquors or washings are 

 not readily coagulated by the addition of alcohol. Castilloa 

 fluids may be preserved for some time with formalin and the 

 rubber globules can afterwards be quickly clotted with alcohol 

 after washing. 



Again, if rubber fluids are allowed to set up a natural fer- 

 mentation in water, rubber is produced on the surface which is 

 of good quality, and has the appearance of being tanned. The 

 proteid matters appear to be destroyed and can be readily 

 washed away. The substitution of the words " rubber fluids " 

 for latex Mr. Parkin deems cumbersome, but this appears a 

 matter of personal opinion only, and I think few people would 

 be found to follow him, and call the red fluids of Pterocarpus, 

 and a species of Croton which gives a liquid indistinguishable 

 from blood, by the name of latex ox milk; and besides their 

 trade names of " Dragon's blood " and " Blood wood " would 

 have to disappear from use, which is hardly probable. It is 

 only fair to mention, as regards preparation or separation by 

 centrifugal action, that even after this process has been used, 

 it is necessary to mass or clot together the rubber particles, 

 and the most ready way of doing this is with a small jet of 

 alcohol. 



I have to thank Mr. Parkin for his reference to the two par- 

 agraphs in vcv<j critique 'i)\\.\i which he is in agreement; but I 

 would point out that I am in no respect responsible for the 

 statements made in the Tropical Agriculturist to which he 

 refers, respecting the production of rubber from young 

 growths, which I have proved by actual experiment to be im- 

 practicable. Mr. Parkin states that the bursting of rubber 

 globules is an open question, but has yet to prove it incorrect, 

 and I recommend him to watch the behavior of the globules 

 under the microscope when alcohol is applied to them. 



Discussions of the matter of the field preparation of rubber 

 mnst be of service now that the actual cultivation of rubber on 

 a large scale is being attempted, and the subject is one which 

 cannot be summarily disposed of in a few experiments. All 

 work in this direction has until lately been only the crude and 

 handy methods of the forest, which it is clear, on the score of 

 economy, must give way to improved methods as the fields 

 come into bearing; for it is in the prevention of waste where 

 the cultivator finds points which will help him to compete with 

 forest production. 



J. H. HART. 

 Botanical Department, Trimdad, February 7, rjoi. 



