CHEMICAL SCIENCE. 233 



crystalline particle liberates a bubble of gas ; the latter is sometimes 

 disengaged, and sometimes is interposed among the crystals; so that 

 the entire mass gradually swells up, increases from 15 to 20 per cent. 

 in its original bulk, instead of diminishing, as it should have done 

 during a normal crystallization of sulphur. 



Instead of making the liquid sulphur penetrate at a temperature 

 approaching its fusing point, caoutchouc may be mixed by means of a 

 mechanical grinding, with 12 or 20 times its weight of sulphur in fine 

 powder ; the properties of the organic substance are not changed, it 

 may be modelled and joined as in the normal and unmixed state. If 

 the temperature be then raised to the degree at which the vulcaniza- 

 tion is effected, it takes place as in the first case, and the above 

 mentioned alterations would likewise be manifested. In regard to 

 the composition and properties of the caoutchouc vulcanized by the 

 means above indicated, it has been found, that when the suitable term 

 has not been exceeded, the organic matter contained sulphur in two 

 different states ; from 1 to 2 per cent, are retained in intimate combi- 

 nation, and the surplus remains simply interposed between its pores. 

 The sulphur in excess, uncombined, is gradually eliminated from the 

 caoutchouc by the mechanical action alternately exerted by the 

 extension which closes the pores, and the contraction which opens 

 them. This effect lasts for several months. Many chemical agents 

 more or less quickly or completely effect the elimination of the 

 interposed sulphur, especially solutions of caustic potassa or soda, 

 with the aid of heat, (and even without heat if renewed several times 

 within a month,) sulphuret of carbon, essence of turpentine, benzine 

 and anhydrous ether. These liquids swell up the organic matter to 

 such an extent that its volume is very soon increased eight or 

 nine times. Ether removes sulphur in a very peculiar manner ; a 

 small portion is first dissolved, and then carried out, when it is separ- 

 ated into crystalline particles ; other particles successively dissolved in 

 the interior follow the same course, and the crystals soon become very 

 bulky, affecting the octahedral form. Neither essence of turpentine, 

 or benzine bring to the outside the crystalline particles of sulphur 

 carried into the thickness of the swelled-up substance. Ether and sul- 

 phuret of carbon, kept for a long time in contact with vulcanized 

 caoutchouc retain in solution 4 or 5 hundredths of caoutchouc, which 

 may be isolated by evaporating several times and redissolving in ether 

 which eliminates the free sulphur, and then by alcohol which removes 

 from 1 to 1-50 per cent, of fatty matter. The caoutchouc thus ex- 

 tracted may be separated into two parts ; one, very ductile dissolved 

 by benzine, which deposits it in evaporating ; the other more tena- 

 cious, and less extensible, is not dissolved. These two parts come 

 from the interior of the plates, at a certain depth where the combi- 

 nation is less intimate and less abundant in sulphur than near the 

 surface. After vulcanization, caoutchouc is also formed of two parts 

 endowed with unequal cohesion and solubility ; this is recognized by 

 keeping a strip steeped for two months in a mixture of 10 parts of 

 sulphuret of carbon and one part of anhydrous alcohol ; the portion 



