TRANSACTIONS OF SECTION B. 785: 
phosphorus trichloride cannot be regarded as a good general method for the 
preparation of acid chlorides ; it gives good results only in the case of the lowest 
members of the acetic series. 
3. On the Constitution of the Alkaloid, Berberin. 
By Professor W. H. Perkin, Jun., F.K.S. 
4. The Production of Camphor from Turpentine. 
By J. EH. Marsy and R. STocKDAue. 
5. On a Double Aspirator. By T. Farruey, F.R.S.E. 
6. On the Vulcanisation and Decay of Indiarubber. 
By W. Tuomson, F.R.S.H., FCS. 
Indiarubber is vulcanised to alter its character, so that it will not become hard 
when exposed to cold, or soft and plastic when exposed to heat. Vulcanisation 
is usually effected by incorporating sulphur with the rubber, and then heating 
the mixture to a high temperature, when the sulphur combines with the rubber, 
producing vulcanised rubber. 
In making waterproof cloth for ‘ macintoshes,’ the rubber cannot be heated to 
a high temperature, as that would be liable to make the cloth tender, or to damage 
the dye on it. In this case the so-called ‘cold vulcanising process’ is employed, 
which consists in the application of a mixture of chloride of sulphur dissolved in 
bisulphide of carbon ; the latter penetrates the layer of rubber, carrying with it the 
chloride of sulphur: and it is generally believed that the sulphur of the chloride of 
sulphur combines with the rubber, producing vulcanisation, whilst the chlorine 
combines with the hydrogen of the rubber, producing hydrochloric acid. The 
author showed by analysis that the chlorine, more than the sulphur, produced the 
vulcanisation, and found about 6} per cent. of chlorine in combination with the 
rubber for every 23 per cent. of sulphur present, part of which was in the free or 
uncombined condition. The higher chlorides of sulphur are liable to produce 
over-vulcanisation, and this is generally explained on the assumption that these 
compounds break up more easily than the lower chlorides, thus giving to the 
rubber an excess of sulphur, The author points out that this is simply due to 
the excess of chlorine which combines with the rubber. 
Vegetable oils are converted into a solid substance resembling rubber by treat- 
ment with a mixture of the chloride of sulphur and bisulphide of carbon, and the 
author finds that here, also, the vulcanisation of the oil is due to the chlorine more 
than to the sulphur present. Vulcanised oil, called rubber-substitute, contains a 
liquid, oily matter, which is generally supposed to be injurious to indiarubber ; and 
as this substitute is employed for mixing with rubber, manufacturers often reject 
‘rubber-substitute’ which contains much of this substance. He found that this 
oily matter, instead of acting injuriously on rubber, like the oil from which it is 
produced, tends to preserve it, by preventing oxidation. 
It is known that copper salts have a most injurious effect on indiarubber, and 
as copper is sometimes used in dyeing blacks and other colours, cloths so dyed are 
liable to decompose and harden the rubber put upon them. A peculiarity investigated 
by the author is that metallic copper placed in contact with thin sheets of india- 
rubber brings about oxidation and hardening of its substance, although no appreci- 
able quantity of copper enters the indiarubber. Metallic platinum also produces, 
but to a much less extent, the same effect ; whilst metallic zinc and silver have an 
injurious effect on the rubber. 
