December 19, 1919] 



SCIENCE 



573 



complete, cool, take up in HCl (1: 6), filter and 

 precipitate sulfates in the usual way, especial care 

 being observed in washing BaSO, free from 

 chlorides. The method is accurate to 0.1 per cent. 



The extraction of rubber goods: S. W. Epstein 

 AND B. L. GoNYO. A report is made of experi- 

 mental work on the rubber extraction of rubber 

 goods, with tables showing results obtained. The 

 observations and conclusions derived from this 

 work were as follows: (1) Extraction for 8 hours 

 with acetone followed by 4 hours extraction with 

 chloroform does not remove all soluble material 

 from some rubber compounds. (2) After a rubber 

 sample has been extracted with acetone it was 

 found: (a) that chloroform in every case ex- 

 tracted slightly more material than carbon bisul- 

 phide; (6) that constant boiling mixtures such as 

 55 per cent, carbon bisulphide — 45 per cent, ace- 

 tone and 68 per cent, chloroform — 32 per cent, 

 acetone extracted from many cheap compounds 

 considerably more material than either chloroform 

 or carbon bisulphide; (c) that usually about 0.1 

 per cent, of sulphur is present in the extract, 

 whether it is obtained by the use of chloroform, 

 carbon bisulphide, or the mixtures under consid- 

 eration. (3) The constant boiling mixture of 68 

 per cent, chloroform and 32 per cent, acetone ex- 

 hibits a marked ability to dissolve vulcanized 

 rubber, as contrasted to the mixture of 35 per cent, 

 carbon bisulphide 45 per cent, acetone which 

 hardly exhibits this ability at all. (4) It is recom- 

 mended that the constant boiling mixture 55 per 

 cent, carbon bisulphide and 45 per cent, acetone 

 be used in plaee of acetone and chloroform to ex- 

 tract rubber samples since: (A) It eliminates one 

 extraction with the necessary weightings. (B) Ex- 

 traction is complete in 8 hours while the acetone 

 and chloroform extractions require a total of 12 

 hours. (C) The extraction of free sulphur is com- 

 plete. (D) A rubber analysis in which the mixed 

 solvent is used, is more accurate than that in which 

 acetone and chloroform are used, because (I.) 

 Little or no rubber is dissolved by this mixture, 

 as compared to chloroform which will in some 

 cases dissolve considerable quantities. (II.) The 

 extraction of cheap rubber compounds is more 

 complete, since the extracts obtained are greater 

 than the sum of the acetone and chloroform ex- 

 tracts. 



The theory of balloon fabric protection: John 



B. TUTTLE. 



The expansion of rubber compounds : C. ■ W. 

 Sanderson. A new apparatus was designed to 



measure the expansion of rubber compounds dur- 

 ing vulcanization. Values of the coeflS.cient were 

 determined for different classes of compounds and 

 found to be between 2.3 X 10-» and 3.8 X 10"*. 

 A study of the relation between the expansion and 

 the increase in specific gravity was made and the 

 conclusion drawn that the increase in specific grav- 

 ity during vulcanization is due to the pressure 

 exerted on the rubber. Other experiments were 

 made to determine the applicability of the meas- 

 urements to commercial practise. 



Volume increase of compounded rubber under 

 strain: H. F. Schippel. The addition of pigment 

 to rubber changes it from a substance which has 

 constant volume under strain, to one which under- 

 goes comparatively large volume increases. The 

 amount of this increase depends upon three fac- 

 tors: (1) the extent of strain, (2) the volume pro- 

 portion of pigment, (3) the average particle size. 

 The larger sized pigments cause greater volume 

 increases, with the notable exception of zinc oxide, 

 which classifies itself under this test with the 

 finer pigments. Prolonged mixing on the mill has 

 only a slight reducing effect upon the volume in- 

 crease. This general property of rubber com- 

 pounds throws light upon their physical condition 

 under strain. 



The determination of cellulose in rubber goods: 

 S. W. Epstein and E. L. Moore. After a discus- 

 sion of the value of a procedure for determining 

 cellulose in rubber goods and consideration of the 

 literature on the subject, the proposed method is 

 discussed. Sample is digested with cresol at 160°- 

 185° C. for 4 hours to dissolve the rubber. Filtra- 

 tion is facilitated by addition of a 200 c.c. of pe- 

 troleum ether. After washing with benzol, 10 per 

 cent, solution of hydrochloric acid, water and ace- 

 tone, the material is dried and weighed. It is then 

 acetylated by heating for 30 minutes at 75° C. in 

 a mixture of 15 c.c. of acetic-anhydride and 0.5 

 c.c. of concentrated sulphuric acid. This is filtered 

 on a weighted Gooeh, washed with 90 per cent, 

 acetic acid and then with acetone and dried and 

 weighed. Loss in weight is recorded as cellulose. 

 Under Results of Analysis are given a number of 

 test compounds, containing varying amounts of 

 cellulose in the presence of various combinations 

 of compounding ingredients. The results by 

 method given indicate its gratifying accuracy. A 

 number of alkali reclaims are given along with 

 cellulose content as obtained by method proposed. 

 It is shown how the percentage of cotton can be 



