THE INDIA-RUBBER INDUSTRIES. 809 



ably full account of them in the manuals of chemistry. In this retort, 

 the dry distillation of caoutchouc is being carried on, and in time 

 very nearly the whole of the India-rubber will be converted into 

 the mixture of oily hydrocarbons, only an insignificant carbonaceous 

 residue remaining in the retort. The mixture of volatile hydrocar- 

 bons, often referred to as caoutchoucine, forms a very good solvent for 

 caoutchouc and certain resinous bodies. 



India-rubber is subject to two kinds of deterioration and decay. In 

 one instance it tends to become soft, and loses its elasticity, while in 

 the other it becomes friable, yellowish, and resinous in its nature. Ex- 

 amples of each kind of deteriorated rubber are on the table, and you 

 will notice that, in the case of this specimen, we have a well-marked 

 instance of both kinds of deterioration going on side by side. The 

 last-mentioned kind of deterioration has been clearly and indubitably 

 traced to an oxidation of the caoutchouc. This oxidation is tolerably 

 rapid when the caoutchouc exists in a finely divided state, and when 

 it is exposed to damp at the same time ; but the alternate damping 

 and drying of the caoutchouc tends more toward its rapid oxidation 

 than does a continual state of dampness. The resinous matter result- 

 ing from the oxidation of caoutchouc has been carefully studied by 

 Spiller, who found that a sample of felt, originally composed of cotton 

 fibers and India-rubber, had become so far changed during six years 

 as to contain no trace of caoutchouc ; but in its place he found a res- 

 inous substance resembling shellac. This resinous body, of which a 

 sample is before you is easily soluble in alcohol, and also dissolves in 

 benzole. Alkalies dissolve it readily, and acids precipitate it from the 

 alkaline solution. It contains 27*3 per cent, of oxygen. 



The conditions under which the softening of the India-rubber takes 

 place are not so well understood, but there is some reason to believe 

 that this is due to incipient oxidation. 



Ozone oxidizes caoutchouc with extreme rapidity, as Warren pointed 

 out in 1877, and I have arranged a simple experiment to illustrate this 

 fact. Through the open end of this glass passes a slow stream of air 

 which has been slightly ozonized ; that is to say, a portion of its oxy- 

 gen has been converted into ozone. When the stream of ozonized air 

 is allowed to impinge on a surface of India-rubber, you see that the sur- 

 face is instantly corroded and roughened. Again, note the effect of 

 allowing: the ozonized air to act on the surface of a distended caout- 

 chouc balloon you see that it bursts immediately. I should mention, 

 by the by, that in the case of these balloons the caoutchouc is slightly 

 vulcanized, but the action of ozone on vulcanized India-rubber is simi- 

 lar to its action on the unvulcanized material. 



It is extremely probable that the rapid deterioration of caoutchouc, 

 which is known to take place under conditions which are not perfectly 

 understood, is frequently due to the corrosive and oxidizing action of 

 ozone. 



