a: i at ie 
—ae ae eee 
ac vel yh 
ON COLLOID CHEMISTRY AND ITS INDUSTRIAL APPLICATIONS. 63 
concludes that ‘ the resins play an active part in the vulcanisation and not merely the 
part of catalyser. Their presence is absolutely essential.’ 
C. Brapte and H. P. Strvens, ‘ The Nature of the Resinous Constituent and its 
Influence on the Quality of Rubber’ (‘ Inter. Congress of Applied Chem.’ 1912, 25, 
581). The authors made comparative vulcanising tests with Hevea and Rambonrg 
(Ficus elastica) rubbers, one compound prepared from acetone (or alcoho!) extracted 
rubber and the other from the untreated rubber. The compound employed consisted 
of the rubber (treated or untreated) and sulphur without other ingredients. They 
noted that the compound prepared from the extracted rubber appeared undercured 
when compared with a control specimen of untreated rubber, but the main difference 
between the vulcanised samples was shown on keeping the vulcanised specimens, when 
_ those prepared from the extracted rubber rapidly hardened and deteriorated (perished). 
H. P. Stevens, ‘The Function of Litharge in the Vulcanisation of Rubber,’ 
Part II., ‘The Influence of the Resinous Constituents’ (‘ Journ. Soc. Chem. Ind.’ 
1916, 85, p. 874). The author describes further comparative tests with resin- 
extracted rubber, using compounds with and without litharge and determining the 
coefficient of vulcanisation. 
(4) Vulcanisation. 
Spence and his collaborators (‘ Koll. Zeit.’ 1911, 8, 304, 9, 83, 300; 1912, 10, 299; 
11, 28, 274; 1913, 13, 265).—The process of vulcanisation is studied in a systematic 
series of experiments, and the conclusions arrived at point to vulcanisation as essen- 
tially a chemical reaction between sulphur and the caoutchouc, the amount of combined 
sulphur being proportional to the time of heating with a temperature coefficient of 
approximately 2°7 for a rise of 10° C. Moreover, when the amount of sulphur is 
limited (e.g., 10 per cent. on the caoutchouc), the whole becomes combined on prolonged 
heating, and with an excess of sulphur the maximum combined sulphur corresponds 
approximately to the formula C,,H,,S, (compare also C. O. Weber, ‘ The Chemistry of 
India Rubber,’ pp. 87-91; also Hinrichsen and Kindscher, ‘ Gummi Zeit.’ 1903, 18, 
251; ‘ Koll. Zeit.’ 1912, 11,191; ‘ Ber.’ 1913, 46, 1291). 
SKELLON, in more recent work, gives a great amount of data which confirms the 
above (‘ Koll. Zeit.’ 1914, 66, p. 96; ‘The Rubber Industry papers read at tho 
Exhibition held in London in 1914,’ p. 172). 
F. W. Hoyricusen and K. Mrrtzmnsure (‘ Ch. Zeit.’ 1909, 33, p.756). Quantitative 
experiments on cold vulcanisation. 
E. Stern (‘ Ch. Zeit.’ 1909, 38, p. 256), ‘ Study of the Reaction between Rubber and 
Sulphur in Solution in Naphthalene.’ 
Harrinrs and Fonrosrert (‘ Ber.’ 1916, 49, 1196 and 1390). Rubber was 
vulcanised in sheets 6 mm, thick by heating a mix containing 10 per cent. of sulphur for 
thirty minutes at 145°C. After sixty days’ extraction with hot acetone, only 0°25 per 
cent.sulphur remained, and it is concluded that this would have been removed if the ex- 
traction had procecded long enough. Itis therefore concluded that vulcanisation is a, 
physicalchange. A distinction, however, is drawn between vulcanisation as carried out 
above, which the authors term ‘ primary vulcanisation,’ and the more fu lly vulcanised 
product obtained by longer heating or by ‘after-vulcanisation’ of the primary 
vulcanised body. 
D. F. Twiss (‘ Journ. Soc. Chem. Ind.’ 1917, 36, 782). This paper contains a 
review of the subject and a very full reference list. The original work contained in it 
deals particularly with the relative reactivities of Su and SA as vulcanising agents. 
Tt is concluded that the modification in which the sulphur is employed is practically 
without influence on the course of vuleanisation. Compare also Dubosc (‘ Le Caout- 
chouce et la Gutta Percha,’ Jan. 1917). 
I. I. Ostromystensxt (‘ Journ. Russ. Physico-Chem. Soc.’ 1915, 47, 1453 et seq., 
1885 et seg.; also 
Vuleanisation of caoutchouc by means of ‘Journ. Soc. Chem. Ind.’ 1916, 35, 370 
halogen compounds, and mechanism of 
the vulcanisation process. 
Hot vulcanisation of caoutchouc by means 93 + 9 » 59 
of nitro-compounds in absence of 
sulphur. 
Hot vulcanisation of caoutchoue by means 35 55 3 sxe 50 
of eae or per-acids, in absence of 
sulphur. 
