Vol. XV. No. 382 



THE AGRICULTURAL I^EWS 



415 



NEW RESULTS IN THE INVESTIGATION 



OF RUBBER. 



An important paper appears in the Agricultural Bul- 

 letin of the Federated Malay States for .July 1916, describing 

 the latest results in the investigation of the question of lack 

 of uniformity in Plantation rubber. Most of this work has 

 been conducted by the Department of Agriculture of ihe 

 Federated Malay States, where recently an experimental 

 vulcanizing factory has been established. 



The quality in Plantation rubber which is most liable 

 to variation is the speed of vulcanization (rate of cure). 

 Readers will probably be aware that vulcanization consists 

 in the combination of rubber and sulphur, and is governed 

 principally by three factors — temperature, period of curing, and 

 proportion of mixture. In rubber experiments it has been 

 usual to work with a constant proportion of sulphur, and 

 ■a constant temperature. If different Plantation rubbers are 

 treated for the same period, it appears that they are not 

 vulcanized to the same degree; one is under vulcanized, very 

 elastic but not strong; another well vulcanized, very elastic 

 and strong; a third perhaps over vulcanized, not very elastic, 

 and brittle. 



This difference in quality is naturally very trying to 

 the manufacturer, and has bred a certain amount of 

 distrust in Plantation rubber. 



Experiments conducted in the Federated Malay States 

 have shown where these dirierences in vulcanizability 

 lie. It was previously known that there is some connexion 

 between the albumen in rubber and vulcanizability. 

 It was also known that certain nitrogenous chemicals could 

 serve to hasten vulcanization, and in the last few years 

 ■a great number of such material also have been patented 

 as aids to rapid vulcanization. But the connexion between 

 these facts, the difference in vulcanizing properties of 

 Plantation rubber, and present day methods of prepar- 

 ation, have only recently been traced. Investigation in 

 the Federated Malay States has shown that it is not 

 the actual albumen which atieets the rate of cure, but the 

 products of its decomposition. It has been proved that these 

 natural decomposition products have the property of acting 

 as accelerators of vulcanization. Also under usual methods 

 of preparation these products occur in quantities differing 

 sufficiently to cause differences in vulcanization. In one 

 of the experiments allowing rubber to stand exposed for 

 a longer time than usual, the time of vulcanization was 

 reduced from three hours to one and a quarter to one and 

 a, half hours — a large difference. 



When rubber is treated chemically so as to get rid of 

 the albuminous matter and the products of its decomposition, 

 it has a vulcanization period of six hours instead of three. 

 Further, rendering the rubber alkaline and keeping it for ten 

 days reduces the period of vulcanization to the rapid time of 

 half an hour. The effect of the alkaline is known to be specifi- 

 cally chemical and not biological as was at first thought. 



The above facts are sutficient to give some idea of the 

 important results that have recently been obtained in the East. 



They have not only shown the previously unknown cause of 

 the differences in vulcanizability of Plantation rubber, but 

 have at the same time sLown how to prepare rubber of 

 rapid or slow vulcanizability at will. 



As to the various factors in preparation that lead to 

 lack of uniformity may be mentioned the age of the trees, 

 climate, the soil, methods of tapping — all of which may have 

 an influence on the composition of the latex and its propor- 

 tion of albuminous matter. The lap.se of time between tapping 

 and coagulating may exercise a great influence, a prolonged 

 period tending to aid rapid vulcanization. The dilution of 

 the latex at the time of coagulation, and the amount of acetic 

 acid will also tend to affect the time required for vulcanization. 

 The additon of anti-coagulants such as formalin and sodium, 

 sulphite tends to prolong vulcanization. The interval between 

 coagulation and rolling is an important point, for it is during 

 this period that the coagulation products are chiefly formed. 

 Rolling may be of great importance. The thinner the crepe, 

 the more serum pressed out of it, the more difficult the rubber 

 will be to vulcanize. Drying and smoking may also be of 

 great consequence. Rapid drying hinders the formation of the 

 vulcanization adjuncts This has been proved definitely in the 

 case of crepe, and in the case of sheet also, which is smoked. 

 Smoking or disinfecting tends to delay vulcanization. It is 

 interesting to note that Para rubber vulcanizes relatively 

 slowly. On the contrary, rubber obtained by ordinary 

 smoking vulcanizes quickly. It is thus desirable to 

 examine .the various constituents- of the serum which 

 cause this different behaviour. 



Many other experiments, besides those described in the 

 first part of this article, have taken the problem of variability 

 in Plantation rubber from the realm of hypothesis to the 

 world of facts, and have shown us definitely that one of the 

 factors causing acceleration in rate of cure is a decom- 

 position product of the protein. It has also been found that 

 another factor present in the latex itself is also involved, and 

 this factor has been the cause of many anomalies which are 

 now being cleared up. 



DEPARTMENT NEWS. 



The Imperial Commissioner of Agriculture return- 

 ed to Barbados by the C.R.M.S. 'Caraquet' on December 

 13, after a visit to Trinidad extending over a fortnight. 



According to Colonial Reports — Annual, No. 894, 

 dealing with the Gold Coast in 191.3, it appears that there 

 is widespread destruction wrought by insect and fungoid 

 parasites amongst the cacao gardens of this Colony due to 

 neglect of the simplest sanitation and cultural work. 

 Coercive measures are advocated for adoption such as are 

 in vogue in towns for the regulation of buildings and the 

 preservation of health. Generally speaking, the only work, 

 done in the cacao garden of tlie Gold Coast is that of 

 cleaning the bush in order to harvest the crop. The care- 

 lessness of the native farmer is encouraged by the want of 

 discrimination shown by the local buyer, who still makes 

 little or no difference in the price he pays for cacao whatever 

 the quality. The production of cacao has continued to 

 increase, however, the exports for 191.5 being greater bjf 

 46 per cent, than those for 1914. 



