174 



SCIENCE 



[N. S. Vol. LIV. No. 1391 



American Society of Animal Production il- 

 lustrates this point: 



PERCENTAGE COMPOSITION OP RATION 

 Peed Ran g-e in Per Cent. 



Corn 85.21 — 90.65 



Shorts 1.53 — 4.11 



Tankage 6.22 — 12.10 



The method of individual feeding which 

 Ashby and Malcomson used seems to be the 

 only method available for the study of some 

 of the problems of animal production and one 

 to which more attention must be given, but 

 there are many factors operative rendering 

 such a method difficult. 



e. eobekts 



Agricultural Experiment Station, 

 TJniversitt op Illinois 



THE AMERICAN CHEMICAL SOCIETY 



(Continued) 

 division op rubber chemistry 

 W. W. Evans, chairman. 

 Arnold H. Smith, secretary. 



The day was devoted entirely to a discussion of 

 the tentative procedure for the analysis of rubber 

 goods. 



Eeports from the executive committee, abstract 

 committee, accelerator committee, and physical 

 testing committee were read. 



Thermal conductivity of some rubber compounds: 

 A. A. Somerville. Rubber mixes have been made 

 containing different amounts of sulphur, with and 

 without accelerators, with equivalent volumes of 

 various fillers, and given a range of cures. The 

 thermal conductivities of these samples have been 

 compared and the results of the test indicate a 

 wide variation in thermal conductivities due to 

 different fillers being used. 



Contribution to the Tcnoioledge of the resins of 

 Eevea rubber: G. Stapfoed Whitby and J. Dolid. 

 A number of crystalline substances 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 roughly 5 

 per cent, of the extract, it decomposes without 

 melting, and forms an optically active acetate 

 crystallizing in leaflets and melting at 169°. With 

 this sterol another substance, not yet isolated in 

 a state of purity, was associated. The soluble 

 sterol consisted of matted, flexible leaflets, melting 

 at 127°. A substance, optically inactive, melting at 



62°, constituting roughly 5 per cent, of the ex- 

 tract, was obtained. Quebrachitol was isolated 

 from the extract, and was found to occur gener- 

 ally in sheet and crepe. The results of a quanti- 

 tative study of the oxidation of caoutchouc under 

 the catalytic influence of copper are reported. 



The solubility of gctses in rubber as affecting 

 their permeability: Charles S. Venable and 

 Tyler Puwa. It was found that when rubber 

 absorbs gas, the gas is held in true solution and 

 not by absorption. In the case of carbon dioxide, 

 which has about an average solubOity, the amount 

 of gas thus held in true solution by the rubber is 

 directly proportional to the pressure and de- 

 creases with increasing temperature. This solu- 

 bility is unaffected by degree of vulcanization or 

 by the presence of compounding ingredients. 

 Other gases seem to behave in a similar manner. 

 Relative solubility values obtained for various 

 gases in rubber show that there is a general re- 

 lationship between the solubility and density of 

 the gas and its rate of penetration through rub- 

 ber. These results, in general, confirm the original 

 hypothesis of Graham that the penetration mech- 

 anism 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 evap- 

 oration at the other surface. The indications are, 

 however, that the actual size of the gas molecule 

 is also an appreciable factor. A striking rela- 

 tionship between the solubility of various gases 

 in rubber and in water has been noted. 



Beactions of accelerators during vulcanisation. 

 III. Carbo-sulphydryl accelerators and the aetion 

 of zinc oxide: C. W. Bedford and L. B. Sebeell. 

 Reactions of accelerators producing mereapto 

 groups by action of sulfur are discussed. Thio 

 carbanilide with aniline in benzol solution will 

 dissolve zinc oxide and wUl vulcanize a zinc oxide 

 cement at room temperature. Other zinc salts of 

 mercaptans such as zinc thiophenol and zinc-ethyl- 

 xanthate vpill vulcanize pure gum cements contain- 

 ing sulfur at room temperature. These accelerators 

 are free from nitrogen or alkali and also func- 

 tion in press or steam cures. Without zinc oxide 

 no accelerator has been found which will vulcanize 

 at room temperature. Zinc salts of carbo-sul- 

 phydryl accelerators furnish the key to the paper. 



The influence of piperidine-piperidyl-dithiocar- 

 bamate on vulcanization: G. Stafford Whitby 

 and O. J. Walker. Tested in a 90 : 10 rubber- 

 sulfur mix, 1 per cent, of the base mentioned is 



