Gums, Resins, 



484 



[June, 1910, 



one well-known product is a solution of 

 a nitro-cellulose in linseed or castor oil 

 which has been nitrated by treatment 

 with a mixture of nitric and sulphuric 

 acids. Other such articles are made by 

 oxidising the nitrated oil with lead 

 peroxide, or by simply heating it in air. 



These oxidised, sulphured, and nitrated 

 oils, in one form or another, are largely 

 used as substitutes for rubber. Of the 

 other substitutes proposed, a few 

 examples may be given, to indicate some- 

 thing of their general nature. 



First, there are those which, while still 

 retaining oil as one ingredient, include 

 also other important constituents. Thus, 

 "Fentou's rubber" is a mixture of oils 

 with tar, pitch, and creosote ; which 

 mixture, when digested with nitric acid, 

 gives a toughened mass, and this on 

 heating yields an elastic product simu- 

 lating rubber, "Russian" substitute, 

 said to be useful for covering telegraph 

 cables, contains as ingredients wood-tar, 

 hemp and linseed oils, ozokerite, sper- 

 maceti; and sulphur. "Oxolin" is made 

 by impregnating fibrous material such 

 as jute or hemp with linseed oil, oxidis- 

 ing the oily mass with warm air, and 

 working the product up between rollers 

 into a coherent mass, which can then be 

 vulcanised by heating it with sulphur. 



In another category of substitutes oil 

 plays only a subordinate part, or is alto- 

 gether dispensed with. Thus "Jones's 

 substitute" is stated to be made from 

 various gums and gum-like products as 

 the chief constituents. In W. H. Per- 

 kin's patent (23,031/07), gelatine or glue 

 is dissolved in creosote and then treated 

 with some reagent— potassium bichro- 

 mate, formaldehyde, or tannic acid— 

 which will render the gelatine or glue 

 insoluble ; after "setting" the mass ob- 

 tained is digested with acetone to make 

 it firmer. "Textiloid" has for its ingre- 

 dients various resins, nitrocellulose and 

 camphor. As a curiosity in this class 

 may be mentioned " grape rubber," 

 produced from the skins of grapes by 

 means of pressure ; it is not, however, 

 a commercial article. Finally, though 

 this can only be a substitute for rubber 

 in very hard articles, we may mention 

 the interesting material, "bakelite," 

 recently introduced by Dr. L. H. Baeke- 

 land. It is a condensation-product of 

 formaldehyde and phenol, which can be 

 moulded as desired, and afterwards 

 hardened. 



In what sense are the foregoing 

 articles and their likes to be considered 

 as "substitutes" for rubber? Some 

 persons are disposed to deny them any 

 right to the title, and would look upon 



them as mere adulterants whenever 

 ixsed partially to replace rubber in what 

 would otherwise be an all-rubber article. 

 Others admit, though sometimes grudg- 

 ingly, that there is a place which such 

 substitutes can usefully fill. Much de- 

 pends on what the article is sold as, 

 and on what use it is to be put to. 

 Not all the special qualities of rubber 

 are wanted in all the products for 

 which it is employed. A door-mat 

 is one thing, a bicycle tyre quite 

 another, where a high degree of elasti- 

 city is not really needed, as, for in- 

 stance, in waterproof goods aud electrical 

 insulating work, there is a legitimate 

 field for substitutes which may serve 

 the required purpose. Even here they 

 may not be equal to rubber, but they 

 find their justification in their lower 

 cost. After all, we do not need razors 

 to cut sticks with. 



It may be said at once that no sub- 

 stitute is equal to rubber in every 

 respect. Chemically, the latter is a very 

 inert substance, much more so than the 

 substitutes. Hence, even if the latter 

 were not otherwise inferior, they would 

 be less durable than rubber under 

 certain conditions. They are nearly all 

 acted upon more or less readily in 

 circumstances where rubber remains un- 

 harmed. The modified oils, in fact, are 

 still oils in the sense that they remain 

 glyeerides, decomposable by alkalies, 

 as also by steam under pressure. If 

 used for articles exposed to these agen- 

 cies, they fail in durability, whatever 

 their excellences otherwise. 



The fact that substitutes of this class 

 are readily saponifiable by alkalis 

 makes it an easy matter to detect them 

 by analysis when compounded with true 

 rubber. As a rule, the proportion of 

 substitute used is from 5 to 25 per cent., 

 and even the smaller quantity is re- 

 cognisable. 



Of the composita rubbers (or "arti- 

 ficial rubbers," as they are sometimes 

 called), one preparation, which has been 

 made in quantity, and is said to be 

 excellent for many purposes, has for its 

 basis Guayule rubber incorporated with 

 certain gums. Another such article is 

 compounded of natural rubber and some 

 other substance of vegetable origin, 

 probably a latex or a gum, reputed to 

 contain the same chemical elements as 

 rubber and in much the same proportion. 

 Such articles are, of course, only parti- 

 ally " substitutes " for rubber, and their 

 cost rises with that of the latter ingre- 

 dient. Moreover, if any very large 

 demand for them arose, there is always 

 the possibility that the supply of gums 

 and latices would become insufficient, 



