June 1, 1921 



THE INDIA RUBBER WORLD 



657 



Meeting of the Rubber Di\ ision of the American Chemical Society 



THE sixty-first meeting of the American Chemical Society 

 was held in Rochester, N. Y., April 25 to 29. Two days 

 were devoted to sessions for consideration of the programs 

 of the various divisions. Those of the Rubber Division drew 

 an average attendance of about sixty rubber chemists. Much 

 interest was shown in the papers, discussions and in the exhibi- 

 tion, under the microscope, of rubber coniiiounded with various 

 ingredients. 



The following is a brief record of the proceedings, with 

 abstracts of the papers presented: 



METHODS FOR THE ANALYSIS OF VULCANIZED RUBBER 



The methods of analysis recommended by the Joint Rubber 

 Insulations Committee were discussed in detail, and various 

 changes of procedure suggested. Elaboration and test of these 

 methods was referred to a committee, as follows : W. W. 

 Evans, The B. F. Goodrich Co., chairman ; F. J. Dugan, The 

 Goodyear Tire & Rubber Co. ; S. Collier, Bureau of Standards ; 

 A. H. Smith, Thermoid Rubber Co. ; W. B. Wiegand, Ames 

 Holden McCready Limited ; Professor H. S. Simmons, Municipal 

 University of Akron. 



THE DIRECT DETERMINATION OF THE SULPHUR OF 



VULCANIZATION' 

 By S. Collier and Michael Levin 



The sulphur actually combined with the rubber is determined 

 by dissolving the rubber and polyprene sulphide in cymene. The 

 solution is diluted with petroleum ether and filtered after the 

 fillers have settled out. The filtrate containing the polyprene 

 sulphide is evaporated to dryness by heating on the steam bath 

 and by means of a gentle current of air. The residue is dis- 

 solved in nitric acid and the solution evaporated to dryness. 

 Three cc. of nitric acid are added to the residue and then five 

 gm. of sodium carbonate. The mixture is fused and '.he amount 

 of sulphur determined. 



THE ANALYSIS OF RUBBER GOODS CONTAINING ANTIMONY 



PIGMENTS' 



By S. Collier and Michael Levin 



The amounts of rubber and antimony are determined on the 

 same sample. A sample previously extracted with acetone is 

 dissolved by heating in cymene. The solution is diluted with 

 petroleum ether and filtered through a Gooch crucible after the 

 fillers have settled out. The antimony sulphide is dissolved out 

 with hydrochloric acid, precipitated with hydrogen sulphide, and 

 determined volumetrically by titration with standardized potas- 

 sium permanganate. A correction for insoluble organic matter 

 is made by drying, wei.ghing and igniting the crucible. The 

 sulphur fillers are determined on a separate sample, which has 

 been filtered from thfe cymenc-petrolenm ether solution and 

 washed with solvent. 



THE SOLUBILITY OF GASES IN RUBBER AS AFFECTING THEIR 

 PERMEABILITY - 



By Charles S. Venable and Tyler Fuwa 



.^n experimental study was made of the various factors 

 influencing the solubility of a gas in rubber. It was found that 

 when rubber absorbs the gas, this gas is held in true solution 

 and not by absorption. In the case of carbon dioxide, which 

 has about an average solubility, the amount of gas thus held in 

 true solution by the rubber is directly proportional to the pres- 

 sure, and decreases with increasing temperature. This solubility 



'Published by permission of the Director of the Bureau of Standards, 

 Washington, T>. C. 



-.'\hstract of paper delivered before the Rubber Section of the American 

 Chemical Sncioty in Rochester, X. V., .\pril 27, I92I. 



is unaffected by degree of vulcanization or by the presence of 

 compounding ingredients. Evidence was presented to show that 

 the other gases behave in a similar manner. 



Relative solubility values obtained for various gases in rubber 

 show that there is a general relationship between the solubility 

 and density of the gas and its rate of penetration through rubber. 

 These results, in general, confirm the original hypothesis of 

 Graham that the penetration mechanism consists in the solution 

 of the gas at one surface of the rubber and the diffusion of 

 the undissolved gas through the rubber and its evaporation at 

 tlie other surface. The indications are, however, that the actual 

 size of the gas molecule is also an appreciable factor. A striking 

 relationship between the solubility of various gases in rubber and 

 in water has been noted. 



THE INFLUENCE OF PIPERIDINE-PIPERIDYL-DITHIOCARBAMATE 

 ON VULCANIZATION - 



By G. Stafford Whitby and O. J. Walker 

 Tested in a 90:10 rubber-sulphur mix, one per cent of the 

 base mentioned is found to reduce the time of cure by seven- 

 eighths, and even at 130 degrees C, to lead to curing in about 

 one-third of the time required at 141 degrees C. in its absence. 

 -At the optimum cure, rubber containing the base showed (a) 

 a noticeably lower sulphur coefficient, (b) a very considerably 

 higher breaking stress, (c) a noticeably smaller elongation, and 

 (d) a lower position of the stress-strain curve (strains as 

 ordinates) than did rubber from which the base was absent. On 

 aging for seven months, vulcanizates prepared w-ith the base 

 behaved in a manner essentially similar to that show-n by vulcan- 

 izates prepared without it ; the stress-strain curves coming 

 down the paper to a similar extent and the breaking points 

 altering in a similar way. 



CONTRIBUTION TO THE KNOWLEDGE OF THE RESINS OF 



HEVEA RUBBER- 



By G. Stafford Whitby and J. Dolid 



A number of crystalline substances, as follows, have been 

 isolated from the acetone extract of plantation Hevea rubber. 

 .At least two of these are sterols. The less soluble of the two 

 constitutes roitghly 5 per cent of the extract. It decomposes 

 without melting, and forms an optically active acetate crystalliz- 

 ing in leaflets and melting at 169 degrees C. With this sterol, 

 another substance, not yet isolated in a state of purity, was asso- 

 ciated. The more soluble of the two sterols consisted of matted, 

 flexible leaflets, melting at 127 degrees C, and showing {°^)t 

 — 25 degrees C."" In addition, a substance, optically inactive, 

 melting at 62 degrees C, and also constituting roughly 5 per cent 

 of the extract, was obtained. Quebrachitol was isolated from the 

 extract, and was found to occur generally in she«t and crepe. 

 Further: the results of a quantitative study of the oxidation of 

 caoutchouc under the catalytic influence of copper are reported. 



RELATIVE THERMAL CONDUCTIVITIES OF SOME RUBBER 

 COMPOUNDS - 



By A. A. Somervllle 



.\ series of thin sheets of rubber with thermocouple junctions 

 between were placed on a steam chest kept at 100 degrees C. On 

 top of this pile a vessel containing melting ice maintained a 

 temperature of degrees C. By comparing the time necessary 

 for the center thermocouple to reach maximum temperature for 

 various stocks a measure of their relative heat conductivity was 

 obtained. The conductivities of stocks containing 3 and 10 per 

 cent sulphur on the rubber and 10 per cent sulphur with 2 per 

 cent accelerator were found the same. This value was taken as 



'Meaning that the angle of rotation of the plane of polarired light was 25 

 degrees counter-clockwise. 



