78 



SCIENCE 



[Vol. LV, No. 1412 



fact tliat it can very readily be methylated to the 

 corresponding tetra-methoxyphenyl derivative. The 

 reaction for preparing the hydroxyphenyl com- 

 pound from rubber tetrabromide and phenol is 

 like a Friedel-Crafts ' reaction, being speeded up 

 by the use of anliydrous aluminum chloride, zinc 

 chloride, etc. Other halogen derivatives of 

 rubber such as the dihydrochloride also react with 

 phenol. 



Microscopy of ruhher fillers. Irene C. Diner, 

 The principal rubber fillers, namely, barytas 

 vrhiting, zinc oxide, lithopone, litharge, red lead 

 antimony sulphide, iron oxide and gas black, are 

 included in a large chart showing the character 

 istics which differentiate these microscopically. 

 Among the properties shown are size, color, shape 

 crystal structure, impurities and optical proper 

 ties. A basis of a positive method of identifica 

 tion of the fillers is indicated, based upon 17 

 different measurable physical properties. It is 

 hoped that this method will in time supercede 

 the present lengthy and cumbersome qualitative 

 and quantitative analysis. Besides being shorter 

 it is more exact since it gives the exact state in 

 which the filler is present rather than merely the 

 amount of each element with a good guess as to 

 their association, for example, whether the sub- 

 stance be present pure or impure, hydrated or 

 anhydrous, etc. 



The use of the microscope and photomicro- 

 graphs in the study of inorganic materials used 

 in rubber. Benton Dales and W. W. Evans. 



Beoent developments in the art of rubber micro- 

 sectioning. Henry Green. A method for 

 making microsectious of rubber has been devel- 

 oped which is free from the various inconveniences 

 associated with the method heretofore employed 

 of freezing the sample with C0_^ and liquid air. 

 The elasticity is destroyed and sufSeient rigidity 

 acquired by treating the sample with dilute SC 

 solution. Sections are obtained % mm x 4 mm 

 in area, which under a magnification of 1,500 

 diameters appears, in round numbers, to be a 

 strip 3 ft. wide and 20 ft. long. This is sufficient 

 to show all the characteristics of the sample. The 

 sections can be made exceedingly thin, beautifully 

 transparent and of uniform thickness. 



Piperidine-piperidyl-dithiocarbamate as a rub- 

 ber accelerator in the presence of zinc oxide: 

 G. S. Whitby and A. H. Smith. One part of 

 piperidine-piperidyl-dithiocarbamate in a 90 rub- 

 ber 10 S, 10 zinc oxide mix cuts the time of vulcan- 

 ization at 141 degrees C from three hours to 

 less than one minute. At 131 degrees C it cuts 

 the time of vulcanization from seven hours to 



one minute. It is fully vulcanized in three to 

 four minutes at 115 degrees. Wien only two 

 parts of S are used the time of vulcanization is 

 one minute at 141 degrees, or two minutes at 131 

 degrees, or ten minutes at 115 degrees. Stress- 

 strain data are given. 



An improved oven for accelerated aging of 

 rubber. C. W. Sanderson. 



General discussion. Accelerated aging tests. 

 Led by W. W. Evans, review of article, Tcji years 

 experience with accelerated aging tests, by W. C. 

 Geer and W. W. Evans. 



An apparatus and method for abrasion tests 

 on rubber compounds: J. C. Sproul and W. W. 

 Evans. 



The determination of true free sulfur and 

 true coeffioient of vulcanization in vulcanized 

 rubber: W. J. Kelly. The application of the 

 method devised for pure gum stocks (J. Ind. 

 Eng., Ch. 12: 875, 1920) to compounded stocks. 

 Free sulfur determined by the ' satured alcohol ' ' 

 method. For combined sulfur the sample is 

 extracted with ale. KOH and ether HCl, the 

 latter removing any sulfide as H^S and dissolving 

 accelerators which form water on ether soluble 

 hydrochlorides. In this way considerable sulfur 

 is removed in addition to that extracted by 

 acetone and which had previously been considered 

 as combined with the rubber. In some cases an 

 additional extraction with water is necessary, but 

 the details of this remain to be worked out. 



Corrected stress-strain curves for rubber: J. W. 

 Shields. An improved method is explained for 

 drawing stress-strain curves for rubber which 

 takes into account the decrease in cross section 

 of the specimen. Such curves do not have the 

 S shape which is characteristic of uncorrected 

 curves. The corrected curves show the modulus 

 of rubber to be least at the smallest elongation 

 and to increase gradually as the specimen is 

 stretched. The method for determining the true 

 modulus of unstressed rubber is illustrated. The 

 equation for this curve is developed and the 

 values of the equation constants given for several 

 stocks. 



The determination of the particle size of pig.- 

 ments. W. W. Vogt. By a turbidimetrie method 

 it is possible to determine the capacity of a pig- 

 ment to extinguish direct light rays. This 

 capacity, called obscuring power, is a direct 

 function of the average particle size of the pig- 

 ment. The values of O. P. are shown to be 

 consistent with particle size as determined micro- 

 scopically and furthermore to be in close accord 

 with the practical compounding value of 'the pig- 



