February 1, 1915] 



THE INDIA RUBBER WORLD 



265 



ANALYSIS OF MECHANICAJ Rl BBEK ( - AND RUBBER 



INSULATION. 



Ash: After an acetone extraction the residue is gently ignited 

 and weighed, making no corrections for the sulphur. This is 

 much simpler than the method recommended bj the- Joint Rub- 

 ber Insulation Committee ("Journal of Industrial and Engi- 

 neering Chemistry," January, 1914, pane 74). They dissolve the 

 residue in Terebene and xylol and tiller through tared filtei 

 paper which is then weighed without incineration. 



Total Sulphur: The sample is treated with nitric acid sat- 

 urated with bromine and evaporated to dryness and fused with 

 potassium nitrate and sodium carbonate. The sulphate thus 

 formed is determined as usual. 



Acetone Extraction: This is performed in a modified Wilej 

 Soxhlet extractor with a sample wrapped in extracted and 

 weighed cheese-cloth, as before described. The residue in the 



cheese-cloth is dried in a hydrogen gas current for five hour.-.. 

 and the loss of weight is called "acetone extract uncorrected." 

 noii and freezing are performed as in crude rubber de- 

 termination above. The product is called "waxy hydrocarbons." 

 Il is evident thai any rubber resins present would thus lie callei 

 "waxy hydrocarbons." Sulphur is determined in the saponified 

 matter as sulphate. The .[In., method is practically identical 

 with that recommended by the Joint Rubber Insulation Com- 

 mittee referred to above. Hut the committee makes a further 

 separation into cases "A" and "B." 



Rubber, ["he sum of the corrected acetone extract, ash, total 

 sulphur and wax) hydrocarbons, is subtracted from 100. and tin 

 difference is called "Rubber by Difference." 



A comparison of these methods with those recommended by 

 the United States Bureau of Standards may be made by referring 

 to The [ndia Rubber World, December, 1914, page 129. 



A Review of Recent Progress in Rubber Chemistry- I. 



Contributed. 



The author of this paper, a 1i I rubber chemist, submitted it, not as in any way a descriptive article, but merely as an 



index of progress during the last two years. To elaborate it and make il a readable article would necessitate the use of many 

 hundreds of pages. 



DURING the last few years there has been considerable 

 progress in the chemistry of rubber, though there have 

 been no striking discoveries which have greatly changed 

 rubber manufacture or been of marked commercial importance. 

 Perhaps one reason for this has been the fluctuation of price 

 in rubber itself and the commercial changes attributable to the 

 rapid advance in the use of plantation brands, together with the 

 lowering of price and disappearance of many brands of rubber. 



As an instance of this may be cited the immense amount of 

 work and money spent on synthetic rubber research while the 

 price of Para was around $2 per pound. Another instance is 

 the partial disappearance of the deresinating industry, owing to 

 the increased price of crude pontianak and scarcity of other 

 brands. of low grade crude. 



The notable book by C. O. Weber, published in 1902, gave 

 English readers the first classified work on the theory and 

 practice of rubber chemistry, though much had been published 

 before in a desultory way. Since that time general chemistry 

 has advanced. Colloid chemistry particularly has received much 

 attention, and, as rubber is one of the best examples of a col- 

 loid, this advance has helped rubber chemist rj 



COLLOID CHEMISTRY. 

 Since the publication of the work entitled "Colloids and the 

 lltra-microscope," by R. Zsigmondy, and translated into Eng- 

 lish by Jerome Alexander, this subject has received much at- 

 tention, especially as the invention of the ultra-microscope has 

 enabled us to actually see the colloid groups. One of the latest 

 contributions on this subject from an American authority, Dr. 

 Wilder T. Bancroft, is a paper prepared for the meeting of the 

 American Chemical Society which was to have taken place in 

 Montreal in August. In this he gives a working theory for 

 colloid chemistry which may be summarized as follows: 



1. Colloid chemistry differs from ordinary chemistry only 

 through the variation resulting from the increasing dispersity of 

 one or more phases. 



2. Selective absorption occurs at the surfaces. 



3. Sufficiently finely divided particles which are prevented 

 from coalescing will be kept suspended by the Brownian move- 

 ment. 



4. Under fixed conditions of peptonization, we get an approxi- 

 mately definite limiting concentration corresponding with a 

 saturated solution in the case of a true solution. ("Journal of 

 Physical Chemistry." 1914, Vol. 18, p. 549.1 



I' Bary ('"Journal of Physical Chemistry." Vol. 10, p. 437) 

 states there are two strict divisions of colloids: Those having the 

 power to form gels on account of their great cohesion and 

 power to dissolve. These arc properly so called. Second, elec- 

 trical suspensions, In the case of gels, the conversion into 

 miscellae is obtained at a specific increase in volume, independent 

 of the nature of the solvent, which may be benzol, chloroform, 

 etc. 



In another article this author (Ibid., No. 3) states, "benzine 

 penetrates slowly, passing by osmosis into the particles." 



OSMOSIS AND SWELLING IN SOLVENTS. 



Some recent work has been done along this line. W. A. 

 Caspari read a paper before the London Chemical Society in 

 which the osmotic properties and physical constants of rubber 

 solutions are described. (The India Rubber World, October, 

 1914, p. 17.) 



F. Kirchof (The India Rubber World, October, 1914. p. 17) 

 has made a thorough investigation on the swelling of vulcanized 

 rubber. 



VISCOSITY. 



At the Eighth International Congress of Chemistry, J. G. 

 Pol, of Delft, presented a paper on the relation of viscosity 

 to the amount of resins in Castilloa rubber (Vol. 9, Report of 

 the Eighth Congress). This paper was discussed there (Ibid., 

 Vol. 27) by E. Marckwald, F. H. Hinrichsen, Eaton and others. 

 Clayton Beadle and Stevens later discussed this subject. (The 

 India Rubber World, October, 1914, p. 18.) P. Schidrowitz 

 ("Chemical Vbstracts," Vol. 13, p. 3669) has further contributed 

 to ur knowledge of this subject. R. Gaumt (The India Rub- 

 ber Wi hi .n. August, 1914, p. 600) has also taken up the subject 

 of the viscosity of solutions. F. Kirchof ("Kolloid Zeitung," 

 1914, Vol. IS, p. 30) has made a study of the influence of the 

 solvent on the viscosity of rubber solutions. 



In general the viscosity coefficients, it is found, run parallel 

 with the numbers which form a measure of the swelling capac- 

 ity of the various solvents toward caoutchouc. Solutions in 

 haloid compounds, such as carbon tetra-chloride, tetra and penta- 

 chlor-ethane, have twice the viscosity of benzol or petroleum 

 benzine solutions. Spence and Kratz (The India Rubber 

 World) have also contributed to this subject. B.J.Eaton ("India 

 Rubber Journal," August 16, 1913) has made some investiga- 

 tions on viscositj It may be noted that most of the workers 



