Gums, Resins, 



286 



[OCT. 1906. 



through the whole mass of the latex. The acid while throwing out the sulphur, 

 causes coagulation of the rubber particles throughout the mass with the result that 

 the sulphur is thrown in contact with every molecule of rubber. You can tell the 

 end of the reaction by the ordinary litmus test which will turn red on the slightest 

 excess of acid. It is advisable not to add a great excess of acid either in 

 the vulcanisation process or in the ordinary process, as there is no doubt 

 an excess of acid has some effect on rendering the rubber more liable to become 

 soft and tacky. I believe the original idea of coagulation with acetic acid was 

 that the rubber particles rose to the surface and then set to a solid mass. That 

 is not the case. Rubber sets throughout the whole body of the liquid, and being 

 lighter that the water it contracts on itself and rises to form a layer on the surface, 



COLOURING OP LATEX. 



[The colouring of latex by organic dyes was then demonstrated, and Mr. Bam- 

 ber went on to say this would be useful for the manufacture of children's toys as 

 there will be no necessity for poisonous colours being put on the outside, as the' 

 colour will be mixed throughout the rubber.] 



You will see that this process will mean an enormous saving of time 

 and labour, and I think myself we aviII ultimately obtain stronger rubber, 

 and instead of using 8 to 10 per cent of sulphur, we will only have to 

 add one or 2 per cent, I have here some samples of rubber produced 

 in this way, the strength of which compares very favourably with rubber 

 as ordinarily produced. At the same time that I was making this sample, 

 I made a biscuit from the same latex without any admixture of sulphur 

 or any ingredient. This was dried and treated exactly in the same way as the 

 other biscuit — under the same conditions and on the same bench — but 

 within a week it ran into a soft tacky condition, whereas in none of the sulphured 

 samples was the slightest tackiness shown. I think this antimony solution 

 and the sulphur itself has a very strong antiseptic effect on the rubber. I should 

 like, if possible later on, to show how vulcanisation actually takes place, as small 

 articles can be done here. Unfortunately the vulcanising press I expected has not 

 arrived, and will not be here for another fortnight. (Applause.; 



DISCUSSION. 



Mr. James Ryan said he had to thank Mr. Bamber for much valuable 

 information, but at the same time he noticed Mr. Bamber had used the Centigrade 

 scale in making his calculations, and he would like to give the figures mentioned in 

 Fahrenheit, as follows :— 



112° Fahr. = 50 Centigrade. 



140^ „ = 60 



262° „ = 112 



291° „ = 144 



They would notice that the lower scale was below the boling point of water, and the 

 higher scale was considerably above it. 



Mr. Bamber :— I am sorry I did not give the three figures. I had them here, 

 but I did not thin k it was necessary. (Laughter.) 



Dr. Willis remarked that the future would be in the possibility 

 which Mr. Bamber had briefly indicated of the vulcauisation, colouring and other- 

 wise treating of rubber in the state of latex instead of allowing it first of all to be 

 coagulated in block or biscuit, whichever it might be, and then breaking it up and 

 practically reconstructing it, as a great many did into sheet, containing sulphur and 

 other compounds intimately intermixed with it. It appeared to him there 

 must be a loss of strength in the rubber by that method of treating it, 



