2 



[July, 1909. 



imagined that in some eases the enzyme 

 favours the subsequent occurrence of 

 tackiness by setting up such conditions 

 as facilitate the initiation of the changes 

 which heat and sunlight afterwards 

 accelerate," 



The author proceeds to describe an 

 experiment in the coagulation of 

 Funtumia latex which had been pre- 

 served in a liquid state by means of 

 ammonia. The ammonia and salts were 

 separated by dialysis, and the latex was 

 then sterilised. Part of the sterilised 

 latex was coagulated by means of 

 decinormal sulphuric acid, while the 

 other was treated with sterilised water 

 only. Absolute alcohol was then added 

 to both, and they were heated to 100°O 

 to obtain complete coagulation in both 

 cases. The rubber obtained by water 

 and alcohol only was a white elastic 

 mass with very good tenacity and with 

 '■ nerve," while the rubber coagulated 

 with sulphuric acid was very sof c and 

 plastic without either tenacity or 

 "nerve," After the samples had been 

 washed and dried, the former was a 

 sample of good rubber, while the latter 

 melted into a soft resinlike paste. Thus 

 from the same sample of latex, two 

 entirely different specimens of rubber 

 were obtained, one sound and the other 

 excessively "tacky," 



The dry weight of the samples proved 

 that no " Oxidation " had taken place, 

 and acetone extraction showed that 

 the percentage of resin was practically 

 the same in both, while further ana- 

 lysis proved that the tackiness was 

 not due to chemical changes. These 

 facts, together with experiments on 

 the viscosity, etc., lead the author 

 to the conclusion that tackiness depends 

 not on chemical changes but on 

 physical changes. Sunlight and heao 

 appear to be the most efficacious agents 

 in its production, but it may also be 

 produced by dilute sulphuric acid. 



The result detailed above is of extreme 

 interest to rubber planters at the present 

 time, since it indicates that the same 

 latex, coagulated by different methods, 

 may produce rubbers varying enor- 

 mously in strength. For several years it 

 has been an article of faith that rubber 

 from young trees is weaker than that 

 from older trees. Certainly the avail- 

 able samples of rubber demonstrated 

 this, and it will require strictly con- 

 trolled, logical, scientific experiment to 

 upset this belief, though, from a botanical 

 standpoint, it must be confessed that 

 there is no valid explanation why rubber 

 from young trees should be weaker. 

 The oft-quoted statements about the 

 greater amounts of resin present in 



young rubber do not agree with the 

 recorded analyses. But one flaw in the 

 argument which supports the current 

 belief may be pointed out, though the 

 possible error may not be so important 

 as it appears. The comparisons between 

 rubber from old and young trees have 

 been made on samples from different 

 estates, possibly coagulated by different 

 methods or by unavoidable variations of 

 the same method. Seeing that different 

 methods of coagulation may produce 

 such strikingly different results, it is 

 evident that, from a scientific stand- 

 point, the question of the strength of 

 the rubber from trees of different ages 

 must be regarded as more or less an open 

 one, until samples have been prepared 

 by the same method and by the same 

 operator. 



Practical observations ou tackiness are 

 all, at present, more or less vague. It is 

 confidently asserted that tackiness is 

 communicable, i.e., that a tacky biscuit 

 infects others in contact with it, but 

 the possibility that, in the supposed 

 instances of this, similar external or 

 internal conditions may have produced 

 tackiness in these biscuits successively 

 is overlooked. It is not sufficient to put 

 a tacky biscuit on the top of an appa- 

 rently sound one, and then to argue that 

 the " disease " has been transferred when 

 the lower biscuit becomes tacky. 



I have been informed by one planter 

 that he can induce tackiness in crepe 

 rubber at will, by including in it scrap 

 rubber which has been allowed to remain 

 on the tree for several days. 



At present no experimental evidence 

 can be offered, but the following 

 instances may be recorded, since they 

 show the improbability that tackiness is 

 due to bacteria or fungi. In November, 

 1907, some biscuits were made from latex 

 from the old Hevea trees at Henarat- 

 goda, and were left lying in the labora- 

 tory at Peradeniya. Some of these 

 were by accident placed on a table where 

 the sunlight fell on them, and these 

 subsequently became tacky. One of 

 these tacky biscuits has been lying on 

 the top of a sound biscuit for over six 

 months, but the lower biscuit has not 

 become tacky. Again, in March, 1908, a 

 sample of crepe (Hevea) which showed 

 pale yellow spots, the first stages of 

 tackiness, was sent in for examination. 

 A piece with a large yellow spot was 

 selected, and, after the yellow area had 

 been accurately marked out, the piece 

 was covered with a bell glass, and left 

 lying exposed to light (not to direct 

 sunlight) on the table. The yellow area 

 subsequently became semi-fluid, but this 

 condition has not spread in the slightest 



