224 



THE INDIA RUBBER WORLD 



[February 1, 1914. 



WHAT THE RUBBER CHEMISTS ARE DOING. 



[Extracts from recent articles on the Chemistry of Rubber Zi'hich 



have appeared in some of the foreii;n publications.] 

 IN the "Guniini Zeitung," Vol. 28, page 126, Utz contributes an 

 * article on the "Examination of Golden Sulphide of An- 

 timony." For the determination of the antimony he recom- 

 mends an electrolytic method suggested by A. Clas.sen (Quanti- 

 tative Analyse durch Elektrolyse, 5th Edition, page 153), which 

 is as follows : The antimony is dissolved in 80 c.c. of a saturated 

 sodium sulphide solution (specific gravity 1.14). To this is 

 added 30 c.c. of a freshly-prepared 30' per cent, potassium cyanide 

 solution, and the whole mixture diluted with water to about 

 140 c.c. This solution is then electrolyzed at a temperature of 

 65 to 70 degs. C, using a current density of 1.2 to 1.3 amperes. 

 After completion of the electrolysis the deposited metal is washed 

 and dried with alcohol at 80 to 90 degs. C. 



The above method is discussed by W. Schmitz in the "Ciunimi 

 /eitung," Volume 28, Pa.gc 453. Numerous authorities are 

 ■quoted in support of the stateincnt that such antimony determina- 

 tions always fall high. For this reason Schmitz prefers the fol- 

 lowing volumetric method, which is based on the oxidation of 

 trivalent antimony to pentavalent antimony by means of potas- 

 /ium broniate according to the following equation : 2KBrO., 

 -f 2HC1 + 3Sb,03 = 2KC1 + 2HBr + 3Sb:05. Very accurate 

 /•esults are claimed for this method, which is carried out as fol- 

 lows : About 0.5 grams antimony, previously dried at 60 degs. C, 

 are dissolved by means of concentrated hydrochloric acid 

 (specific gravity 1.19) on the water bath. The heating is con- 

 tinued until lead acetate paper shows the evolution of sul- 

 phuretted hydrogen to have ceased. There is thereupon added 

 an excess of tartaric acid crystals, the solution thluted with water. 

 and filtered from any insoluble matter. A few c.c. of hydro- 

 chloric acid are thereupon added to the solution and the latter 

 titrated with potassium bromate, using either methyl orange or 

 indigo as an indicator. The potassium bromate solution is made 

 up by diluting 2.7850 grams to a volume of 1 litre. Such a soki- 

 tion corresponds to 6 mgs. antimony per c.c. 



R. Ditmar contributes an article in the "Chemil<cr Zeitung," 

 No. 115. 1913. on the Coloring of Rubber Goods. It is pointed 

 out that up to within recent date it has been impossible to use 

 organic dyestuffs for coloring rubber goods which are steam or 

 dry-heat cured. The dyestufifs referred to do not withstand the 

 high temperature of vulcanization and accordingly mineral pig- 

 ments have to be resorted to. It has been found, however, that 

 the so-called vat dyes do withstand vulcanizing conditions and 

 may be effectively used in place of the mineral pigments, the 

 result being that a much larger variety of shades thus becomes 

 available. Not only vat dyes, but all dyestuffs containing re- 

 vertible groups, withstand vulcanizing conditions. Such dye- 

 stuffs are anthra quinone derivatives. 



.■\ British patent, No. 18506/1912, has been issued to Arthur 

 Heinctnann for the improving of synthetic rubber. It has been 

 found that the soft condition very frequently inherent to syn- 

 thetic rubber is due to the fact that certain portions are in a 

 lower state of polymerization. It is therefore desirable to re- 

 move these insufficiently polymerized portions. These latter por- 

 tions are insoluble in acetone and soluble in benzol, and there- 

 fore cannot be separated by the utilization of either of these 

 solvents. It has been found, however, that ethyl acetate dis- 

 solves the insufficiently polymerized portions while the highly 

 polymerized product is not affected by this solvent, provided the 

 solvent is present in excess. 



British patent No. 11530/1912 has been granted Farben Fa- 

 briken vorm. F. Bayer & Co. for the accelerating of vulcaniza- 

 tion. It has been found that piperidine and its homologues ma- 

 terially increase the speed of vulcanization. F'or instance, 100 

 parts Para rubber, 10 parts sulphur and 5 parts piperidine are 

 vulcanized for 15 minutes it a temperature of 135 to 145 degs. C. 



The resulting product contains 3.5 per cent, combined sulphur. 

 In the absence of the piperidine a period of one hour will be 

 necessary to accomplish the same degree of vulcanization. Pyri- 

 dine. (|uinoline and dimethyl aniline do not exhibit this accel- 

 erating property. 



In the "Kolloid Zeitschrift," Volume 13. Page 49. F. Kirchhof 

 contributes an article on the "Oxidation of Rubber." He points 

 out that vulcanized rubber is more liable to oxidation than the 

 unvulcanizcd product. By exposing vulcanized rubber contain- 

 ing varying amounts of combined sulphur, from which the free 

 sidphur has been removed by extracting with acetone, it is found 

 that about 1/3 of the total combined sulphur is readily oxidized 

 to sulphuric acid, while 2/3 of the total combined sulphur is 

 oxidized together with the combined rubber molecule. This 

 result is in bearing with Erdmann's Thiozonide hypothesis of 

 vulcanization, which regards 3 sulphur atoms of the following 



configuration : S 



\ 



S 

 / 

 S 



as entering into combination with the rubber molecule at the 

 double bond. It is that sulphur atom which is in combination 

 with the two other sulphur atoms which Kirchhof suggests is 

 o.xidized to sulphuric acid. The two remaining sulphur atoms 

 being in direct union with the rubber molecule remain with it 

 even in the process of oxidation. 



In the "Gummi Zeitung," Volume 28, Page 237, G. Huebener 

 subjects the above communication of Kirchhofs to a criticism 

 and himself carries out experiments similar to those of Kirch- 

 hofs, using hard rubber instead of soft rubber, which was used 

 by the former investigator. He is unable to confirm results ob- 

 tained by Kirchhof, and finds much more than 1/3 of the sulphur 

 to be easily oxidized into sulphuric acid. For this reason he 

 is of the opinion that in the case of hard rubber by no means is 

 all the sulphur which can be removed w'ith acetone to be re- 

 garded as combined sulphur. He is of the opinion that in hard 

 rubber only a small amount of the free sulphur is extractable 

 with acetone. 



RUBBER MANUFACTURING STATISTICS IN THE 



NEXT CENSUS. 

 A S announced in another column, the Rubber Club of Amer- 

 ^ ^ ica has commenced taking a census of production, by which 

 the extent and character of the industry will be clearly shown. 

 The two main points on which information is sought are the 

 size of the staff and the value of output in the principal branches 

 of manufacture. 



The information [)criodicallv issued by the Census Bureau as 

 to the rubber industry has dealt with these points and likewise 

 a number of others, as shown in the abstract of the figures for 

 1899, 1904 and 1909 compiled by The Indi.\ Rubber World, 

 which appeared in the issue of May 1, 1912, page 374, and showed 

 the distribution under various broad divisions of the grand total 

 of more than $200,000,000 a year. 



But apart from the disadvantage of the census returns being 

 issued only once in five years, is the fact that the classification is 

 too broad, including: (1) belting, hose and packing; (2) boots 

 and shoes, and (3) other goods. While dealing with the 1909 

 census figures. The Iniii.v Rubber World found this wide classi- 

 fication too general and has for some years been in communica- 

 tion on the subject with the Director of the Census. Acting 

 upon the suggestions of this journal, the Bureau has been pre- 

 paring a special rubber industry form to be used by manu- 

 facturers for the census of 1914, in which the number of sep- 

 arate articles for report has been increased. Jileanwhile the 

 valuable work of the Rubber Club will (particularly if repeated 

 periodically) prove of much benefit to the industry. 



