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THE INDIA RUBBER WORLD 



[December i, 1903. 



and rubber is a colloid, have the property under certain condi- 

 tions of inducing the colloidal state in many crystalizable bodies. 

 May not therefore the rubber colloid be capable of inducing the 

 colloidal state in sulphur vapor? 



The rate of vulcanization depends largely on the medium by 

 which it is surrounded. If it be surrounded by air, it proceeds 

 slower than if surrounded by any other medium in use. This 

 is because air both receives and yields up heat very slowly. It 

 cannot be heated to any appreciable extent except by contact 

 and circulation, and it cannot give up its heat any more readily 

 than it receives it. As rubber is a nonconductor of heat, we 

 have here the worst possible combination for the transmission 

 of the heat necessary to maintain the vulcanization at any par- 

 ticular temperature. When the surrounding medium is steam 

 the rate of vulcanization at any particular temperature proceeds 

 somewhat faster, as saturated steam yields up its heat quite 

 freely if kept in circulation. If the medium be water under 

 pressure, the circulation of the water maintains the desired 

 temperature, and the loss of sulphur by evaporation is almost 

 entirely prevented. 



If the rubber being vulcanized is between heated iron plates, 

 a quick vulcanization results, in consequence of the rapidity 

 with which the plates yield up heat to the rubber. If the rub- 

 ber be subjected to great pressure between the plates, the rate 

 of vulcanization is still more rapid by reason of a closer con- 

 tact between the iron and the rubber, which enables the latter 

 to receive a greater supply of heat. By the latter method, a 

 piece of rubber may be vulcanized in a few minutes, while sev- 

 eral hours might be required to vulcanize it in air at the ordi- 

 nary pressure. Thus the rate of vulcanization is not governed 

 by the conductivity of the surrounding medium, for air, steam, 

 and water are nonconductors, but at the rate at which the 

 medium can yield up its heat. 



There is a popular delusion that the manufacture of vulcan- 

 ized rubber is an exact science — one which can be conducted in 

 accordance with certain rules, with the certainty that, if so con- 

 ducted, the product will always be vulcanized rubber goods 

 which have the physical qualities necessary to render them dur- 

 able and adapted to the various purposes for which they are in- 

 tended. This delusion is not confined to the general public, 

 but is held by many well educated persons who have had no 

 practical experience in the art. 



There is no fixed rule for the manufacturer to follow in the 

 preparation of his goods for the vulcanizing operation, nor for 

 the time or the temperature to be employed during that opera- 

 tion, and, from the nature of the case, there can be none. Each 

 manufacturer has his own formulas and his own methods of at- 

 taining results, which must be strictly followed in minute de- 

 tail to be of any practical use. The slightest deviation in any 

 step of the process influences the final result. So well known is 

 this to manufacturers that little effort is made to keep formulas 

 or methods secret ; in fact, " the possession of formulas, with- 

 out the general ability, experience, and discretion that their 

 proper use requires, is a damage rather than a blessing." 



To accomplish the chemical union of rubber and sulphur, the 

 time depends on the temperature, and the temperature on the 

 time during which it is maintained. Whatever the tempera- 

 ture may be, within the limits usually employed, the rubber 

 and sulphur continue to unite but the time must be adapted to 

 the temperature. Again, a percentage of combined sulphur 

 which in one rubber would produce sound merchantable goods, 

 would, in another rubber result in a product having no com- 

 mercial value whatever. Hence a chemical analysis of a sam- 

 ple cannot necessarily deteimine its commercial value. 



All formulas for vulcanization must be adapted to the kind 



of rubber employed, to the compounds incorporated with it, 

 and to its previous manipulation. If in the same operation 

 there be submitted to the vulcanizing process articles made 

 from various kinds of rubber all prepared and compounded 

 alike, some will be perfectly vulcanized and commercially val- 

 uable, but the remainder may have no commercial value, be- 

 cause different varieties of rubber require different methods of 

 compounding and preparation, and also different times and 

 temperatures during vulcanization. And so if several pieces of 

 the same kind of rubber, even pieces of the same lump of crude 

 rubber, be handled differently in the preparatory steps, the 

 compound in each case being identically the same, and then 

 all be submitted together to the same vulcanizing operation, 

 some will be well vulcanized and commercially valuable, and 

 the others may have no commercial value. For different de- 

 grees of mastication of crude rubber produce different physical 

 conditions, and all such differences in physical condition are 

 perpetuated by the vulcanizing process. Again, if various rub- 

 ber samples, identically the same in every respect, be vulcan- 

 ized by different processes, they will be physically unlike, even 

 if vulcanized at the same temperature and with the same per- 

 centage of combined sulphur. 



As Weber says: " There is no definite relation at all between 

 the quantitative chemical result and the physical technical ef- 

 fect of the vulcanizing process, inasmuch as the same degree of 

 vulcanization in the same kind of rubber need not result in the 

 formation of identical vulcanization products." 



With such numerous chances for the production of defective 

 goods, manufacturers are extremely averse to making any 

 changes either in materials or processes without having first 

 convinced themselves, by the fullest investigation and experi- 

 ment, of the utility of the proposed changes. This tendency 

 of the manufacturers insures the public against the marketing 

 of inferior or defective vulcanized rubber articles. 



GERMAN OFFICIAL INTEREST IN RUBBER. 



THE German minister of commerce, Herr Mdller, has been 

 visiting some of the leading rubber goods factories in his 

 country, with a view to becoming personally acquainted with the 

 conditions of the industry. Such a visit was made recently to the 

 large works of the Continental Caoutchouc- und Guttapercha- 

 Cie., at Hanover, where the minister was escorted in automo- 

 biles from his hotel by several of the municipal officers, being 

 welcomed at the factory by Directors Seligmann and Prinzhorn 

 and the president of the board of control of the company. Af- 

 ter being shown through the establishment, the minister spoke 

 in flattering terms of the condition in which he had found it. 

 He was especially pleased with the efforts made by the com- 

 pany for the welfare of their employes, and expressed much in- 

 terest in the plans for houses for the workmen, for which the 

 company had offered competitive prizes. The Gummi-Zeitung 

 feels that the minister of commerce, by such visits, will be im- 

 pressed with the importance of the rubber industry in Germany, 

 and be led to feel that it deserves every encouragement by the 

 government. 



A Town Divided over Rubber Heels.— The question of 

 rubber heels for high school pupils is agitating Farmington. 

 The principal has ruled that all must wear them and the 

 school board upholds him, while many of the pupils and their 

 parents feel that the order is infringement upon their personal 

 privileges. Last week a score of pupils weie expelled for re- 

 fusing to wear the prescribed heels, and the war is now on in 

 earnest, — Portland (Maine) Press. 



