428 



THE INDIA RUBBER WORLD 



[Ai-Rii. 1, 1920. 



to be accurate by analysis of known compounds. The method 

 has been shown to be useful in the detection and determination 

 of cellulose in reclaims. 



II. The presence of leather in mixings docs not interfere with 

 determination of cellulose. 



III. In the analysis of light, cheap compounds such as rubber 

 soles where wood, jute, cork and leather may be present, it is 

 desirable to digest sample at 120 degrees C. in cresol for 

 16 hours, in order to keep these fibers intact. Acetylauon obtains 

 95 per cent of the total wood; 90 per cent of the total jute; 21 

 per cent of the total cork, and 70 per cent of the leather. 



IV. The amount of cork present in a mixing can be approxi- 

 mated by removing unacetylated cork residue and considering 

 this as 70 per cent of the total. 



V. In the absence of jute, wood and cork, it is shown that the 

 amount of leather may be estimated approximately. 



VI. The problem of separately determining wood, jute and 

 leather in a mixing has not been solved. 



DETERMINATION OF NITROGEN IN CRUDE RUBBER. 



The exact nature of the nitrogen compounds in crude rubbei 

 has hot yet been determined, but the assumption that they may 

 be converted into ammonia has been demonstrated by Howie who 

 has adopted Wilfarth's modilication of anhydrous copper sul- 

 phate to the Kjeldahl method. 



It is generally considered that the final stage in the digestion 

 with sulphuric acid is reached when the solution becomes clear. 

 Actually it is necessary not that the solution be clear but to 

 completely change the nitrogen compounds present into am- 

 monia. Because of the large proportion of hydrocarbons in 

 caoutchouc, at least six hours are necessary to produce a clear 

 solution. 



To determine if this period can be shortened and still have 

 a complete change of the nitrogen to ammonia, the following ex- 

 periments were carried out. In each instance one gram of 

 caoutchouc was digested with 30 cc. of sulphuric acid, sever, 

 grams of potassium sulphate, and about one gram of anhydrous 

 copper sulphate. Identical samples were heated, respectively, for 

 one. two, three, four, five and six hours, after which the per- 

 centages of nitrogen were determined in the ordinary way. The 

 sample heated for six hours was the only one clear, but was 

 colored. The others all contained more or less carbon in sus- 

 pension. 



The analytic results showed that it is unnecessary, at least for 

 caoutchouc, that a clear solution be obtained and that from three 

 to four hours is ample for obtaining the total nitrogen present. 

 {"Le Caoutchouc ct la Gutta Pcrcha.") 



THE CONSTITUTION OF VULCANIZED RUBBER. 



W. C. Schmitz summarizes as follows his investigations and 

 contribution to the knowledge of the constitution of rubber by 

 means of bromination, which appears in "Gumim-ZciHtng." vol- 

 ume 34, No. 10, page 193. 



The impression that the bromine method would enlarge our 

 insight into the problem of vulcanization has been confirmed to 

 some extent and further results may be anticipated. 



The author's investigation has shown that the bromine absorp- 

 tion is purely additive, there being no substitution. The reaction 

 proceeds in two stages when continued for 18 to 20 hours, ten 

 atmospheres of bromine being absorbed by the caoutchouc mole- 

 cule in the first stage, two molecules of hydrogen bromide being 

 afterwards liberated. The residue tetrabromide differs from the 

 known caoutchouc tetrabromide by being insoluble in carbon 

 tetrachloride. Full details of the method are given and the same 

 reagent is being applied in the study of vulcanized rubber. The 

 questions so far clearly defined in the latter connection are as fol- 

 lows : 



1. Is vulcanization a purely additive combination of rubber 

 with a sulphur combination ? 



2. Is the sulphur combination the result of substitution? 



3. Is the purely colloidal explanation of the sulphur combina- 

 tion adequate, or are stoichiometric laws and colloidal factors 

 involved? 



4. Are the improved physical qualities of vulcanized rubber the 

 result of pure chemical process ? 



SYNTHETIC RUBBER FROM PETROLEUM. 



Synthetic rubber from petroleum, and the process for making it, 

 as described in a treatise by Professor Ossian Aschan, of the 

 University of Helsingfors, are discussed by Giuseppe Bruni, of 

 the Pirelli laboratory at Milan, in a recent issue of the "Giornale 

 di Chimica Industrialc." 



The Italian chemist concedes that the method may be em- 

 ployed with success for commercial quantities as well as in the 

 laboratory. Though not wholly certain of this, he demonstrates 

 that even with a material as common as Russian petroleum to 

 draw upon, the cost of production would be prohibitive. It seems 

 hopeless that synthetic rubber from any source can compete with 

 natural rubber while the latter can be produced at a profit at the 

 prices now prevailing. 



ACTION OF PHENOL IN RECLAIMING. 



.\ndre Dubosc, in "Le Caoutchouc ct la Gutlu I'crcha," July 

 15, 1919, states that a better quality of reclaimed rubber is ob- 

 tained by phenol than by the alkali process. The action is ex- 

 plained in two ways: (1) depolymerization of the rubber mole- 

 cule; (2) formation of phonolic ethers or sulphides such as 

 phenyl sulphide or thiophenol, the heat of the formation of which 

 is greater than that of vulcanized rubber. Either water or 

 alkaline solutions of phenol are used. 



CHEMICAL PATENTS. 

 THE UNITED STATES. 



FLE.xiBLE He.st-resisting Cojiposition. An inflatable expan- 

 sible core tube for use in the curing of sulphurized rubber 

 tires is formed of rubber mixed with telurium or selenium which 

 gives the material great durability when subjected to repeated 

 heating. (H. E. Smith, United States patent No. 1,322,734.) 



Heat Resisting Packing consisting of vulcanized rubber 

 compound having magnesite in a state of fine subdivision in- 

 corporated and distributed therein. (Julius Stromeyer, Philadel- 

 phia, Pennsylvania United States patent No. 1,330,148.) 



Packing. A molded and vulcanized piston packing ring com- 

 prising in its composition rubber, sulphur and ground sponge. 

 (George Christensen, Jamaica, assignor to H. W. Johns-Man- 

 ville Co., New York City, both in New York. United States 

 patent No. 1,330,979.) 



Dope or Substitute for Ceixuloid, Vulcanite, etc. A plastic 

 composition comprising a phenol-formaldehyde condensation 

 product, camphene and a cellulose derivative. (William Thomas 

 Robiiison-Bindley, Wimbledon, and Arthur William Weller, both 

 of Lundon, England. United States patent No. 1,331,127.) 



Co.MPOSlTIO.M FOR USE AS SUBSTITUTE FOR LEATHER. A dense 



non-elastic composition of matter comprising rubber, fintly 

 ground sponge and a considerable proportion of inert filler in- 

 timately mi.xed together. (George Christensen, Jamaica, N. Y., 

 assignor to H. W. Johns-Manville Co.. New York. United 

 States patent No. 1,332,320.) 



Process for Treating Latex and Product Obtained by 

 coagulating rubber producing and similar latex, restraining the 

 expansion of the latex during coagulation in the absence of ap- 

 plied fluid pressure, whereby the latex will be subjected to a 

 gradually increasing pressure during its coagulation, and adding 

 a vulcanizing agent thereto. (Edward Mark Slocum, Medan, 

 Sumatra, Dutch East Indies, assignor to General Rubber Co., 

 New York City. United States patent No. 1,332,925.) 



