410 



THE INDIA RUBBER WORLD 



March 1, 1921 



enters into the compound as hydrogen sulphide or sulphur dioxide. 

 "The researches of Graham and others on the osmose of various 

 gases through rubber have shown that both the gases mentioned 

 above are absorbed in considerable ijuanlities by rubber, which 

 means that they diffuse readily. The reaction between sulphur 

 dioxide and hydrogen sulphide is — 



2H=S + S0,=2H,0 + 3S 

 the products being water and nwnatoinic or colloidal sulphur. 

 All of this sulphur which was present as sulphur dioxide or 

 hydrogen sulphide diffused through the mass of rubber has been 

 transformed into colloidal sulphur capable o{ uniting with the 

 rubber and saturating the double bonds of the caoutchouc mole- 

 cule." 



PEACHEVS REPLY 



"By what chain of reasoning Dubosc considers himself entitled 

 to father the new cold process of vulcanization as a consequence 

 of the publication by him of a hypothetical explanation of the old 

 hot process is by no means clear, and the writer would welcome 

 further enlightenment. 



"Dubosc states that only one form of sulphur is in evidence in 

 the vulcanization process in the ordinary hot sulphur cure, namely, 

 the colloidal form, and that the first step in the process is the 

 breaking down of ordinary, or polymerized, sulphur into colloidal, 

 or depolymerized, sulphur. 



"This statement is contradicted by the very axioms of colloidal 

 chemistry, which affirms that colloidal bodies possess a high 

 degree of polymerization, and that the more complex the mole- 

 cule, the more pronounced is the colloidal character. 



"Dubosc overlooks the fact that the temperature at which vul- 

 canization is effected in the hot process (140 degrees C.) lies well 

 above the melting point of sulphur (114 degrees C), and that 

 molten sulphur (which at 140 degrees C. consists of an equi- 

 librium mixture of two well-recognized forms of the element) 

 can alone be concerned in the change. It should be noted that 

 the present writer claims that vulcanization is effected by means 

 of atomic sulphur produced momentarily by the interaction of 

 hydrogen sulphide and sulphur dioxids at the ordinary tempera- 

 ture. To convince physical chemists that atomic sulphur is iden- 

 tical with colloidal sulphur will indeed prove a difficult task. 



"Dubosc further states that when pure rubber and sulphur are 

 heated together to the vulcanizing temperature, the amount of 

 sulphur entering into combination with the rubber is very small. 



and that the product does not possess the characteristics of 

 vulcanized rublKT. This statement is not based on facts. Pure 

 rubber has never been prepared, but rubber which has been 

 subjected to the most drastic method of purification available 

 will still vulcanize, even up to the ebonite stage, when heated with 

 sulphur. It is purely a matter of ihe amount of sulphur and 

 the duration of the heating. 



"The statement, 'When resins arc heated witli sulphur 

 hydrogen sulphide is produced,' calls for one comment only, viz., 

 that the natural resins are not hydrocarbons but are oxy-com- 

 pounds usually of an acid character. The further statement that 

 the heating of the 'insoluble portion' of rubber with sulphur leads 

 to the formation of both hydrogen sulphide and sulphur dio.xide 

 would re(iuire that oxidation and reduction of sulphur should 

 proceed simultaneously in a single reaction, which is in the highest 

 degree improbable. 



"As regards the suggestion that sulphur dioxide plays a part 

 in the hot vulcanization process and that the requisite amount 

 is derived from the interaction of the sulphur with a metallic 

 oxide in the presence of air, it is sufficient to mention that a 

 solution of rubber in xylene, free from and out of contact with 

 air, and containing no metallic oxide whatever, can be effectively 

 vulcanized by heating with sulphur to a temperature of 135 to 140 

 degrees C. for several hours. The writer would ask M. Dubosc 

 to suggest the source of the sulphur dioxide in this particular 

 experiment. 



THE CASE OF PURE EBONITE 



"How can Dubosc's hypothesis be made to fit the case of the 

 production of pure ebonite, made by heating together 100 parts of 

 plantation crepe and 50 parts of sulphur between platens of a 

 press at 140 degrees C. sufficiently long to yield a product con- 

 taining 32 per cent of sulphur? If Dubosc's theory were correct 

 and the sulphur combining with the rubber were produced by the 

 interaction of hydrogen sulphide and sulphur dioxide, then for 

 every 100 gr. of rubber converted into ebonite, about 20.000 cc. 

 of the former gas and 11,000 cc. of the latter would requ're to 

 be generated by the interaction of the sulphur with the resins and 

 the occluded air in order to effect the complete vulcanization. 

 Does M. Dubosc suggest that plantation crepe contains sufficient 

 quantities of resins and occluded air to yield the amounts of the 

 two gases calculated on the basis of his hypothesis?" 



Consumption of Automobile Tires in 1920 



RUBBER co.viPANY STATISTICIANS in Akron estimate that the 

 9,295,252 motor vehicles registered in the United States in 

 1920 require about 32,000,000 tires annually to replace those 

 worn out at the rate of 3y^ tires per vehicle. This estimate admits 

 a small allowance for solids used on trucks. 



Tire consumption thus averages about 2,700,000 each month, ex- 

 clusive of tires needed for new equipment. 



Estimates of tire consumption have not as yet, so far as known, 

 been based on tire mileage and gasoline consumption. Such a 

 basis, however, offers an opportunity to estimate probable rather 



Table I 



1917 



Gasoline, 

 Gallons 



January 



February 



March 



AlTil 



May 



June 



July 259,630.336 



August 268.478,623 



September 245,473,851 



October 207.n49„-i71 



November 166,703.910 



December 163,183,611 



Totals 2.694,704,251 



•Estimated 



