September 24, 1920] 



SCIENCE 



297 



these data the mimber of molecules at each 

 IK)int has been calculated to be two. 



This means that the molecule of ice must 

 be of the form (HjO)^ or H^O^. The full data 

 and calculations wiU be published in the 

 Physical Beview. D. M. Dennison 



Bbeeakoh Laboeatoet, 

 General Electric Co., 

 Schenectady, N. T., 

 August 20, 1920 



THE AMERICAN CHEMICAL SOCIETY. 

 VIII 



RUBBER DIVISION 



W. K. Lewis, chairman 

 Arnold H. Smith, secretary 



Discussion of report of committee on "Physical 

 Testing. ' ' 



A direct method for the determination of rubber 

 hydrocarbon in raw and vulcanized rubber: W. K. 

 Lewis and W. H. McAdams. It has been shown 

 by a volumetric method involving a double titra- 

 tion that the bromine consumption, corrected for 

 the observed substitution is a true measure of the 

 actual amount of pure rubber hydrocarbon known 

 to be present. Although the amount of substitu- 

 tion increases with the length of the bromination 

 period, the addition corresponds quantitatively to 

 the actual amount of pure ruibber hydrocarbon 

 present when the bromiaation time is from two to 

 four hours. Experimental data is given to show 

 that the actual per cent, of (CioHu)™ in vulcan- 

 ized soft rubber can be determined by a volu- 

 metric bromination method herein described, in- 

 volving a second titration to correct for the sub- 

 stitution which accompanies the particular analy- 

 sis by titrating in dim daylight, this substitution 

 correction can be made very small. 



The value of shoddy in mechanical rubber goods: 

 J. M. BiERER. A chart was presented which gave 

 the cost relations between scrap rubber and re- 

 claimed rubber. The value of this reclaimed rub- 

 ber was evaluated on a basis of tensile strength 

 and compared to a corresponding priced new rub- 

 ber. A line of demarkation through the center 

 of the chart showed where it was more economical 

 to use new rubber or reclaimed rubber. 



The recovery of volatile solvents: W. K. Lewis. 

 Solvents used in the rubber industry m'ay be re- 

 covered by the use of any method such as ab- 

 sorption, compression or cooling. Ordinarily in 



the rubber industry the solvent vapor is diluted 

 with a large quantity of air and in this case the 

 absorption method is best. When such conditions 

 are present so that one has concentrated vapors a 

 compression method becomes available. Benzol 

 used in pregnatiug cord tire fabric may be re- 

 covered with an efficiency of 90 per cent, by 

 enclosing the impregnating apparatus and pass- 

 ing the vapors through an absorption tower. The 

 danger of fire or explosion may be eliminated by 

 passing flue gas into the apparatus. 



On the determination of true free and true com- 

 bined sulphur in vulcanizing rubber: W. J. 

 Kelly. At present sulphur is considered as free 

 and combined. Acetone soluble sulphur may be 

 partly combined with resins, etc., as may also the 

 sulphur insoluble in acetone, heretofore consid- 

 ered as combined with rubber. The total ace- 

 tone extract is soluble in EtOH, but if EtOH sat- 

 urated with sulphur is employed, none of the 

 truly free sulphur will dissolve and hence can be 

 separated from the remainder of the extract. Ee- 

 sults show about 0.4 per cent, sulphur combined 

 with resins, etc. About 85 per cent, of Heva 

 resins are saponifiable and hence any resinous 

 sulphur compounds insoluble in acetone may be 

 soluble in ale. KOH. Acetone extracted sample 

 is boiled 8 hours in 5 per cent. ale. KOH and 

 about 0.26-0.30 per cent, sulphur extracted. Suc- 

 cessive extractions do not increase this. Hence, 

 the rubber is not being decomposed. These re- 

 sults are on pure gum and sulphur stocks and 

 wiU be extended to compounded stocks later. 



Analytical determination of the coefficient of 

 vulcanization: S. "W. Epstein. 



Small amounts of magnesia and certain organic 

 substances as accelerators: G. D. Kratz and A. H. 

 Flower. The activity of small amounts of extra 

 light magnesia as an accelerator was compared 

 with the effect of similar amounts of certain or- 

 ganic accelerators. The load required to effect a 

 given extension was foimd to be a fair measure 

 of the rate of cure of the mixture which contained 

 magnesia; however, this was not true for the 

 mixtures which contained the organic accelera- 

 tors. The accelerating activity of magnesia in 

 small amount was found to be of secondary or 

 contributory, character, acting in conjunction with, 

 or in response to, certain extraneous substances, 

 probably nitrogeneous, present in the rubber. 

 The amount and nature of these extraneous sub- 

 stances was found to limit the activity of mag- 

 nesia as an accelerator. 



