390 



THE INDIA RUBBER WORLD 



[April 1, 1917. 



water, leaving the air-cock open to allow the air to escape. The 

 air-cock shall then be closed and a pressure of ten pounds per 

 square inch applied. 



The test shall then begin by taking original measurements with 

 the pressure at 10 pounds. 



Pressure tests shall be measured with a standardized gage. 

 The increase in pressure shall be made at the rate of 100 pounds 

 per minute and the hose under test shall be held for measure- 

 ment not more than two minutes. 



The unit specification may sometimes modify the foregoing 

 procedure in regard to the pressure at which measurements are 

 to be taken and the period of time to hold pressure wliile meas- 

 urements are being made, in which case the procedure as stated 

 in tlie unit specification shall be followed. 



When called for in the specifications hose shall be subjected 

 to bursting pressure when laid out straight, when curved in a 

 circle of 21 inches radius and when kinked short ofif. 



When the hose is bent flat on itself with a sharp kink and 

 securely fastened in that position for the kink test, the distance 

 from the tail piece of the coupling to the kink shall be accord- 

 ing to size and kind as follows : 



Kind nnd Size. Distance to Kink. 



IJ^-inch fabric and rubber hose 15 inches. 



lYi- and 3-inch fabric hose 18 inches. 



lYi- and 3-inch rubber hose. 24 inches. 



EXPERIMENTS ON THE REMOVAL OF COMBINED 

 SULPHUR FROM REGENERATED RUBBER. 



By D. Repony. 



/'CONSIDERING the numerous patents issued for processes of 

 ^^ reclaiming rubber scrap, there are a large number of rubber 

 chemists, and m.any others, who are trying to regenerate vulcan- 

 ized rubber with the object of removing the combined sulphur. 

 ,.It is not my intention to criticise the value or worthlessness 

 pf the average patented process, yet it is not unjust to maintain 

 , that the above problem is yet unsolved. 



Moreover, it is not my object to describe how this can be ac- 

 complished. My intention is merely to give to the readers of 

 The India Rubber World my experimenting experience on this 

 problem, with the hope that it may be of value. 



Regarding the solubility of vulcanized rubber, when it is passed 

 in solution by boiling with kerosene, etherical camphor oil, oils, 

 liquid tars, nitrobenzol, turpentine, salol, etc., the solubility is 

 more affected by the heat employed than by the solvent. 



Under the temperature 130 degrees C. the solution is very 

 slowly obtained, and above 190 degrees C. it is readily obtained, 

 while heating above 200 degrees C. partially decomposes the 

 rubber. 



Vulcanized rubber in such solution is not affected in its chemi- 

 cal composition, nor with reference to its combined sulphur. 



EXPERIMENTS. 



1. Common reclaimed rubber intermi.\ed with powdered 

 caustic soda and subjected to steam heat in the autoclave from 

 140 to 170 degrees C. for a period of 5 to 12 hours. 



2. Just as above, but intermixed with lead filings. 



3. Intermixed with lead acetate. 



4. Intermixed with iron filings. 



5. Vulcanized rubber (auto tires) broken down in smaller 

 pieces and brought in solution with linseed oil at a temperature 

 of 180 degrees C. is poured in boiling 30 per cent caustic soda. 

 The linseed oil becomes saponified and the rubber completely 

 reprecipitated. 



None of the above treatments has removed any of tlic com- 

 bined sulphur nor improved the product in any way. Of course, 

 the two treatments with caustic soda have removed all the free 

 sulphur, but this I do not consider as an advantage. Liquid tar 

 has great affinity to combine with sulphur, evolving it as HjS. 



6. Vulcanized rubber pieces immersed in liquid tar and ex- 



posed in an autoclave to a temperature of 150 degrees C, after 

 8 hours, will assume the form of heavy cement. This product 

 was afterwards treated with a mixture of benzol and alcohol to 

 effect the separation of the rubber. This resultant product, after 

 analysis, proved to contain all the combined sulphur previously 

 present. 



7. Repeated above experiment, with the exception that it was 

 boiled on a hot iron plate so that the product was not exposed 

 to any external pressure that would hinder the formation of HjS 

 gas. No better result was obtained, however. 



EXPERIMENTS WITH NASCENT HYDROGEN. 



8. \'ulcanized rubber was brought in solution with kerosene, 

 mixed with zinc dust, to which was added dilute hydrochloric 

 acid. Upon stirring and boiling this mixture a large amount 

 of hydrogen sulphide was evolved. Repeated this experiment on 

 rubber free of free sulphur and sulphides, but the same reaction 

 took place. After the treatment the kerosene was extracted with 

 alcohol and refined by means of alcohol and finally washed with 

 water. The obtained product analyzed, showed that some com- 

 bined sulphur was removed, but in its place was substituted 

 chlorine, and the rubber was badly influenced by the acid. More- 

 over, this product gave a very poor physical test for reclaimed 

 rubber. 



9. Repeating above experiment by substituting dilute sulphuric 

 acid in the place of hydrochloric acid, no hydrogen sulphide was 

 evolved, but the rubber was not in any manner changed. 



10. Repeating the same experiment with a solution of oxalic 

 acid, the result was the same as with sulphuric acid. 



11. Repeating again the same experiment using dilute acetic 

 acid, and in another case highly diluted nitric acid; in both 

 cases the rubber was oxidized to a powdery substance. 



12. Other experiments with nascent hydrogen, the latter being 

 produced by bases replacing H:.. by metals. 



Na OH] f O Na 



Al + Na OH I = 2 AL J O Na -f 3 H, 



Na OHj [O Na 



-Aluminum dust admixed to high grade reclaimed rubber, and 

 rolled out to thin sheets, the latter being immersed in strong, 

 boiling Na OH solution, the reaction takes place vigorously. Of 

 course, in this case the evolution of H;S cannot be expected. 

 Analysis of this pro,duct proves that no part of the combined sul- 

 phur has been removed. 



13. Repeated the same procedure as above, but instead of 

 aluminum dust, zinc dust was used. 



14. Again employed the same reaction with nascent hydrogen 

 by using sodium oxalate instead of metals. 



Na 2 Q O. -t- 2 Na OH = H; + Na, C O3 

 In the two last experiments the reaction was accomplished 

 vigorously, but in no case was the combined sulphur removed, 

 and the obtained product has shown all the same properties that 

 it possessed originally as common reclaimed rubber. 



15. One pound of metallic sodium thoroughly mixed with 8 

 pounds of high grade reclaimed rubber became hot within a 

 half minute after being removed from the mixing rollers. This 

 is partly due to the moisture present in the reclaimed rubber, and 

 partly to the rapid absorption of moisture from the atmosphere. 

 The reaction was so rapid that before I was able to plunge it 

 in boiling water a part of it had ignited. Yet I was able to 

 obtain a large enough sample, which had been subjected to the 

 proper reaction and not burned. Examination proved that by 

 this treatment nothing had been gained; however, nothing had 

 been spoiled. 



-Among all these experiments doubtless the reaction of nascent 

 hydrogen developed from zinc dust and dilute hydrochloric acid, 

 substituting chlorine for the combined sulphur, is the only in- 

 teresting one, and may serve as basis for further research work 

 on this difficult problem. 



