278 



THE INDIA RUBBER WORLD 



[May I, 1909. 



per cent, resin, respectively. Seven samples of Upper Congo 

 gave 13.8 per cent, resin. One sample of Brazilian strips showed 

 28 per cent, resin. Three samples of Mexican guayule showed 

 25.4 per cent, resin and 25 per cent, shrinkage, and seven samples 

 of Pontianak showed 75 per cent, resin and 60 per ceni. 

 shrinkage. 



In analyzing these samples they were dissolved in benzol and 

 the resin was precipitated by 'addition of alcohol, the gum re- 

 maining in solution. Dr. Weber, in his work on the analysis of 

 rubber, advises that samples be treated by the method of Soxhlet 

 extraction, using acetone as a solvent of the resins while the 

 rubber is not dissolved. 



These two processes of analysis are mentioned as they typify 

 the processes which have been used in the large way to separate 

 the resin from the gum. What the effect of the resins is on the 

 gimi does not seem to be well known or recognized, and it is 

 evident that if these resins differ greatly in their character their 

 effects would differ considerably. As examples of this, it may be 

 stated that the resin from Pontianak gum is a hard resin, melt- 

 ing above the boiling point of water, and that it is not affected 

 by sulphur at the vulcanizing temperature. It has certain 

 physical resemblances to the ordinary rosin or colophony, but it 

 differs greatly in chemical characteristics. 



On the other hand, the resin from guayule rubber is at ordi- 

 nary temperatures a tarry mass of exceeding stickiness. It is 

 quite susceptible to the action of sulphur, which gradually hardens 

 it. but it at no time is flexible, but when completely hardened is 

 glassy and brittle. Now it is evident that these two resins would 

 act entirely differently in a compound, both while working and 

 when cured. 



Of the other resins — that is, those found in other rubbers — 

 very little seems to be known of their action, but as all rubbers 

 with high resin contents sell for lower prices than those with 

 low resin contents, there seems to be no reason to assume that their 

 action is in any case advantageous or their presence desirable. 



Most of the analyses which have been published relate to the 

 higher grades of rubbers, whose resin contents are in all cases 

 small, and in these rubbers the influence of the resin is probably 

 negligible in all cases. Of late years there have come on the 

 markets great quantities of low-priced rubbers, such as guayule 

 and Pontianak, whose resin contents are high. These rubbers 

 are offered at prices such that their actual contents of pure gum 

 can be obtained much more cheaply than the same amount of 

 gum can be obtained in the higlier .grade of rubbers which 

 do not contain any appreciable amounts of resin. It would 

 seem, therefore, that the trade recognizes these resins as being 

 injurious. 



If these injurious resins can be extracted from the low-grade 

 rubbers without injuring the gum itself, and in a practical and 

 , economical way, it would enable these cheap products to he used 

 in many cases for a higher class of work than they have been 

 used for in the past, and the extraction of the resins would 

 therefore seem desirable. 



A number of manufacturers have had their attention called to 

 the possibilities of this work, and a number of experiments have 

 been made on a commercial scale, and some plants have turned 

 out large quantities of deresinated rubber and are still at work, 

 while others have worked for a time and have then discontinued 

 operations. Most of the deresination has been done at rubber 

 goods factories, and most of the product has been used in the 

 same works, so that little has appeared on the market, and few 

 know of the extent of the industry. Very little has been pub- 

 lished on the subject, and almost nothing made public as to 

 processes or results. 



A number of patents have been taken out in connection with 

 deresinating rubber, however, and it is evident that considerable 

 thought has been given to the subject. In looking over the patent 

 specifications it is seen that the processes of deresination divide 

 themselves into s'everal classes, as follows : 



( I ) Those processes which depend on the action of alkali on 

 the resins. (2) Those in which a solvent is used which, when 

 hot, may dissolve both the rubber and resin, but when cooled 

 will precipitate out the gums. (3) Those which are a solvent 

 for both rubber and resin, and then precipitate out the gum by 

 addition of another solvent, which will keep the resin in solu- 

 tion. (4) Those which use as a solvent a volatile liquid in 

 which the resins are soluble, but which does not dissolve the 

 rubber to an appreciable extent. 



In the next forthcoming issue some of the patents in this field 

 will be reviewed. 



THE COLOR OF RUBBER HEELS. 



COME of the larger factories are making a specialty of rub- 

 *^ ber heels on certain lines of women's and mostly in house 

 shoes, says American Shoemaking. In all cases half of the heel 

 is of leather. This heel has bothered some of the finishers, be- 

 cause the rubber would not finish the same color as the leather 

 on the edge, and as a result the edge had two colors. In one 

 of the leading factories, however, they have gotten over this 

 trouble. The edge is blacked and when dry is put on a coarse 

 bristle brush which has been covered with cloth. The operator 

 applies wax repeatedly to the brush or wheel on every few shoes, 

 which helps keep the blacking on the edge. The inore often 

 wax is applied the better for the edge. It should be stated 

 that these rubber wheels were a very dark color in the first place, 

 which helped the finish. It is the rubber heel light blue or grey 

 in color that gives most troulile to finishers. 



HEELING RUBBER HEELS. 



NoTWiTHST.\NDiNG that there is an attachment used on a heel- 

 ing machine to put on rubber heels [says American Shoemaking] 

 still there are making rooms in which that attachment is not 

 used and a good many rubber heels are put on too. In one bot- 

 toming room' the heeler was seen sticking the rubber heels to 

 the leather base and then the boy who helps the heeler would 

 nail the rubber heels on by hand. .As a rule all shoes with 

 rubber heels have a base of leather, making the finished heel half 

 leather and half rubber. In this case the heeling would have te 

 be styled double deck work, which tneans twice as much work 

 on every heel, besides the slow hand method. The attachment 

 would spank tlie rubber heel on the same as it would a regular 



top-lift. 



AUTOMOBILES IN THE UNITED STATES. 



IN the pages of The Hub (New York) — but we don't know 

 where it got them — are some figures showing the number of 

 automobiles registered in the several states for four years past. 

 The numbers given arc: 29,868 in 1905; 56,158 in igo6; 75,783 

 in 1907; and i29,,36i in 190S. The table is not offered as being 

 complete, but even if it were the total number of cars mentioned 

 as having been registered in any year does not indicate correctly 

 the number of new automobiles actually put into commission. In 

 the first place in New Jersey every machine in the state must be 

 registered anew every year, and this is probably true in some 

 other states ; besides, many of the registrations are duplicated. 

 This is particularly true of a large number of cars which are 

 registered both in New York and in New Jersey. At the same 

 time not a few of the machines registered in former years 

 have gone out of use. It would seem impossible, therefore, to 

 determine just how many automobiles there are in the United 

 States, but the number no doubt amounts to half of all now in 

 use in the world. 



In view of the limited quantities of gutta-percha leaves avail- 

 able for the factory in Soerabaya, Java, money has been raised, 

 says the London and China Telegraph, for the establishment 

 of a similar factory at Bandjermassin, in Dutch Borneo, where 

 gutta-percha leaves are more plentiful. 



