August 1, 1915.] 



THE INDIA RUBBER WORLD 



595 



knows how, using good rubber and any fillers he thinks best. 

 He will be on an equal basis of competition with any other 

 manufacturer as regards quality of the finished article, He 

 must necessarily deliver an equal weight of vulcanized rubber 

 gum of quality to meet the physical tests. 



Function m Litbakcj in Vulcanization Dr, Henrj 1'. 

 Stevens (Journal British Society of Chemical Industry, May 31, 

 1915), presents the result of his experimental studj ni this sub- 

 jecf lh< -i.tti of vulcanization of a rubber product is ju 

 by its aging and physical qualities generally, ["hese are corn 

 lated with the coefficient of vulcanization — that is the percentage 

 in" "combined" sulphur calculated en the ruhher in tlu- product. 

 Too high a coefficient indicates overcure and too low a coefficient 

 an undercured condition. The correcf coefficient varies with the 

 raw ruhher and type of mixing; 2.S to 3.0 having been found to 

 correspond with the sum of best physical condition of freshly vul- 

 canized soft rubber. The effect of litharge in promoting vulcan- 

 ization is usually attributed t" the rise in temperature resulting 

 from the reaction ; 4 PbO + 2 S. = 3 PbS • PbS( >,. I Ine part 

 of sulphur is almost the exact amount required fur the conversion 

 of seven parts of litharge in had sulphide or sulphate. Assuming 

 2.5 as the coefficient of vulcanization of the rubber, it follows 

 that a mixing containing 100 parts of rubber, 5 parts of sulphur 

 and 17 parts of litharge will contain sufficient sulphur to correctly 

 vulcanize the rubber and also to convert all of the litharge into 

 lead sulphide. When tlie mixing contains a larger proportion of 

 litharge than this there will he insufficient sulphur to fully vulcan- 

 ize the rubber and convert all the litharge to lead sulphide. If 

 rubher and litharge are practically equal in their avidity for sul- 

 phur, this will allow the use in practice "f an excess 'if litharge 

 without danger of overcuring the product, provided tin- amount 

 of the sulphur is restricted. The analytic data presented hear 

 out this view and show thai the coefficient of vulcanization falls 

 when the proportion of sulphur is insufficient Pi convert all of the 

 litharge to lead sulphide, and at the same time leave sufficient 

 to cure the ruhher fully. 



In his investigation the author employed air-dried plantation 

 sheet ruhher of good quality. The conclusions reached were: 

 i \ i That the addition of litharge in moderate quantities increases 

 the coefficient of vulcanization. ( 1'. i That the maximum co- 

 efficient of vulcanization is obtained where there is just sufficient 

 sulphur to cure the ruhher fully and to convert all the litharge 

 to lead sulphide and sulphate. (C) That increasing proportions 

 ■ if litharge cause a progressive reduction in the coefficient of 

 vulcanization, a larger percentage of lead sulphide and sulphate 

 being formed. (I>i That the percentage of free sulphur drops 

 suddenly at the point where the ruhher i- full) cured. (E) 

 That even with large proportions of litharge a little free sul- 

 phur always remains. 



RESEARCH. 



'i'he work of C. Marries and E. Fonrobert on the constitution 

 of tlie caoutchouc molecule (Journal Societj ol I hemical In- 

 dustry. I'M?, pp. 277-279) indicates that it must have a molecular 

 formula at least C-. H,„ M . 



O. Lichtenberg (Journal Society of Chemical Industry, 1915, 

 pp. 279-280) shows the close relation of the chemical regenerates 

 obtainable from caoutchouc and gutta percha. The transforma- 

 tion products of caoutchouc hydrogen halides and their thermal 

 dissociation are described. 



The swelling of caoutchouc in organic liquids has been studied 

 by D. Spence and G. D. Kratz (Journal Society of Chemical In- 

 dustry. 1915, p. 280. The capacity to swell in contact with or- 

 ganic liquids is not common to all kinds of caoutchouc, but is 

 limited to the raw material. Para caoutchouc, which has been 

 washed, dried and milled, is no 1' niyer capable of swelling. This 

 change is occasioned by even slight milling or rolling. The 

 swelling power of Para caoutchouc varies with the samples. If 

 the liquids obtained from the solvents are arranged in decreasing 



to the volume ni liquid absorbed by one gram of 

 caoutchouc the series is i l i carbon tetrachloride and chloroform, 

 (2 i carbon bisulphide, (3) benzene, toluene and xylene, ami I 4 I 

 ether 



[TED TREATMl I I I] RUBBEF 



Rubber paint is manufactured by the British Patent Subrite 

 1 o Ltd., under British patent No. 7,087, 1914 (E. G Meadway). 

 Gum mastic is added to a solution of ruhher in naphtha and the 

 mixture added to a solution "t celluloid in amy! acetati 



Vcceleratoi Briti h patent No. 7,370 (1914) granted to S. J. 

 v, relates to hastening vulcanization by a compound re- 

 sulting from interaction of an amine of the cyclic sine-, with an 

 aldehyde of the aliphatic or of the cyclic series; , r of an aldi 

 of the cyclic series with ammonia 



I rn-iziNG Wasti Kiimiik Iii British patent No. 10,030 (1914) 

 granted to II. dare, vulcanized ruhher is reduced to a paste by 

 grinding in water and then c ed under heavy pressure. 



Separating I'm i , Gutta Percha or Balata 



i H-. In German patent No. 280,848 (1913) granted to H. 

 Colloseus, instead of alkali specified in former patent (259,253) 

 any substance is added to the latex which reacts with alkaline 

 earth or salts of heavy metals with fi.rmatinn of compounds in- 

 soluble in water, such as water glass, borax, sodium phosphate, 

 .i. The double decomposition of sodium sulphate with salts of 

 alkaline earths readily coagulates the latex. The same result is 

 produced by carbon dioxide in preseno of alkaline earths. 

 Emulsifying agents named include soap, albumin and the serum 

 remaining after coagulation of caoutchouc. 



Vulcanizing Proci In British patent No. 13,571 (] 



granted to A. Cockburn, solid tires and other massive articles 

 are rendered non-porous bj vulcanizing under pressure of about 

 one ton per square inch by means ,,f a liquid tilling the annular 

 between a steel or iron mold and the article. The article 

 is wrapped in a suitable flexible covering before being placed in 

 the mold. 



Fabrics as foundations in vulcanized rubbei g Is : ■ 



served from injurious effect of sulphurous and sulphuric acids 

 li\ impregnating with (1; additive compounds of ammonia 

 with salts such as zinc sulphate and magnesium sulphate; 

 (2 acetii or ..if. i organic acid, which i- afterwards acted on 

 by ammonia or other alkali; (3) ammonia and carbon diox- 

 ide applied together in succession, preferably under pn 

 during vulcanization; <4i ammonia applied alone, preferably 

 during vulcanization. [W. E. Muntz. English patents 

 4,910—1913 and X... 3,158—1914.] 



S. J. Peachey, (British Patent X... 4263, Februarj 19, 1 



Para-nitr -dimethylaniline or its homologues, such a- para- 



nitroso-methylanaline, or para-nitros'o-ethylanaline are employed 

 to accelarate vulcanization. In an example. 100 parts of rubber 

 are mixed with 10 parts of sulphur and 0.5 part of acceler; 

 agent, the mixture being heated for 20 minutes at a temperature 

 of 135 degrees 145 degrees Centigrade. 



Leather ok Rubber Substitute.— English patent X... 13,128 

 (19141 has been granted to E. If Cook for a composition of 

 in tter containing rubber, reclaimed rubber, sulphur, litharge, a 

 filler sucli as tripolite, coloring matter and leather fibers. 

 destruction of rubber by microbes. 



It is said in the "Revue Scicntiiique" that mi.- , ,, no t 

 attack commercial rubber which is kept in dry air. but when a 

 small amount of moisture is present certain bacteria and moulds 

 derive nourishment from the albuminoids, resins and sugars 

 which the rubber contains Some microbes form on the rubber. 

 making spots of various colors — red, yellow, black or brown — 

 but the ruhher is not materially altered thereby ( in the other 

 hand, two species of actinomyces, very common in garden earth 

 and in canals, actinomyces elastica and a. Justus, assimilate the 

 hydrocarbons of the rubber, and are in consequence capable of 

 modifying its properties in such a way as to deprive it of all 

 mercial value. 



