Februaky I, 1905.] 



THE INDIA RUBBER WORLD 



143 



AN ENGLISH OPINION OF AFRICAN RUBBERS. 



TO THE Editor of The India Rubuek World: The 

 " sweating," or as we call it in this country, " heating,'" 

 of Congo rubbers referred to by Mr. A. D. Thornton in his in- 

 teresting letters in your October and December issues is only 

 too well known here. It is not confined to rubbers specifically 

 known as coming from the Congo, but occurs more or less in 

 all second and low grade Africans, coming from Liberia round 

 to Madagascar. 



Both the " heating " and the "falling" in the drying room 

 referred to by Mr. Thornton are due (i) to the decomposition 

 of albunienoid matter in wet rubbers and improperly coagu- 

 lated rubbers, and (2) to the melting at comparatively low tem- 

 peratures of the various resins which are contained in all rub- 

 ber without exception, but which occur in superabundance in 

 these low Africans. A large percentage of resin may be pres- 

 ent in a rubber which shows no excessive decomposition of al- 

 bumenoid. But so far as I am aware marked decomposition is 

 always accomplished by large amounts of resin of specially low 

 melting point. 



Confining ourselves to these African rubbers, one finds on 

 purchasing a " lot"^it may be merely one cask — that it con- 

 sists of sundry smaller lots collected and coagulated by differ- 

 ent men or gangs of men, one more careless than another, or, 

 it may be, using a different coagulating process. Hence one 

 finds that the amount of decomposition and the percentage of 

 resin varies from ball to ball, and from cask to cask, of the con- 

 signment. Also, no two consignments are alike. It is decid- 

 edly the old Roman law of caveat emptor, with a vengeance. 

 The proper thing for the rubber man to do is to have every 

 consignment, as it reaches the works, carefully graded by some 

 responsible person into at least two qualities and, keeping a 

 careful eye on their behavior in the drying room, to arrange 

 for the drugman to weigh out definite proportions of the worse 

 with the better, and to add to these a definite proportion of 

 some other rubber to leaven the lot before compounding. 



The best course of all that one could adopt is to let these rub 

 bers severely alone. They are always more or less a nuisance 

 and a danger to one's peace of mind by reason of their variabil- 

 ity. It is true, that, when correctly vulcanized, they do not nec- 

 essarily decompose //r se, and they are quite suitable for com- 

 mon molded goods. But the "cure" requires some watching 



They are not, however, worth the prices they fetch in open 

 market at the present time, and the price ratio which they bear 

 to Para should be very much less than it has stood at for a 

 number of years. In fact, the game is scarcely worth the candle, 

 as. apart from the risk and annoyance which they are liable to 

 give in the works, their true " Caoutchouc contents "compares 

 most unfavorably for cost with that of Para fine, whilst it is 

 worth very much less. A good compounder can turn out rub- 

 bers quite as good for the money, and with less worry to himself 

 by working with more reliable material. 



To put the matter in a nutshell, then, the rubbers of commerce 

 contain more or less of the following constituents, viz : 



1. Stones, earth, sand, leaves, grass, wood, and, sometimes, 

 dead men's bones ; 



2. Water ; 



3. Carbohydrates (sugar-like bodies) ; 



4. Nitrogenous matter (albumenoid) ; 



5. Resin or resins (M. P. varying from 20° to 80° C.) ; 



6. A mixture of two or more Caoutchoucs or true rubbers. 

 A very nice list, and one that should be impressed upon the 



shins (it is useless to hit him on the head) of our African 

 brother. 



Now No. 6 is all that the rubber man wants. He has no use 

 for No. 5, except at y.dd. per hundredweight or thereabouts. 

 And he does not want the others at any price, except perhaps 

 the stones and sand, which might be useful in the state of 100 

 mesh powder. 



The species of plant from which the milk is drawn deter- 

 mines, to some extent at least, the percentage of resin (from i 

 per cent, in Pard fine to 60 per cent, in African flake). 



The coagulation of the milk and manipulation of the rubber 

 before it reaches market determine the percentages of carbo- 

 hydrate and albumenoid, as well as the decomposition of the 

 latter or both. j. cardwell quinn. 



Birminf;ham, England, December 14, 1904. 



MR. THORNTON ON AFRICAN RUBBERS. 



TO THE Editor of The India Rubber World : In your 

 January edition appears a letter from Mr. Wilmer Dun- 

 bar, of the Pennsylvania Rubber Co., in which he treats on my 

 previous letters in your Journal. He deducts from them that 

 my object is to get an explanation of some factory troubles we 

 may have had, but such is not the case. 



My object in writing to your Journal was to find out why we 

 cannot obtain Congo rubbers in a more stable condition — why 

 they cannot always be free from stickiness, instead of some- 

 times being nice clean hard lots, and sometimes sticky and of 

 poor quality. Again, Mr. Dunbar says that, owing to the pres- 

 ence of resin, these rubbers are more liable to decompose than 

 are other rubbers. I disagree with him entirely ; resins do not 

 decompose crude rubber. Their presence may, and does, cause 

 some oxidation, but that is quite the opposite effect of the 

 trouble we are considering. Oxidation tends to make rubber 

 hard and brittle — such acondition as we observe in clear resin — 

 but most decidedly not soft and sticky; otherwise we would 

 be afraid to use Almeidina, Tuno, and Pontianak gums. 



Again, let us look for a moment at a bag of African rubber ; 

 some of it is hard and strong, the next ball is partly sticky ; 

 further on we see a mass which is wholly sticky .With the aid 

 of a Soxhiet extractor, using acetone as a solvent, we proceed 

 to determine the amount of resin in each, and invariably we 

 find them identical. Time and again have I done this, and if 

 resin is the cause of the trouble, why is there any difference in 

 the consistency of the several samples .' 



Of course I fully realize that there can be no " hard and fast 

 rule " used with Congo rubbers, but why ? That is what I want 

 to get at. If Pard is constant, why not Congo ? 



My theory is that the trouble is with the gatherer, who, not 

 realizing the importance of his work, stumbles through it in a 

 haphazard sort of way, some of the /a/^.r being coagulated and 

 some not, the latter being the cause of the decomposition, de- 

 stroying the elasticity and curing properties, and quite destroy- 

 ing its natural tendency to swell when dissolved in benzine. 



A. D. THORNTON, 



[General Superintendent Canadian Rubber Co. of Montreal.] 

 Montreal. Canada, January 17. igo^. 



A rui'.RER manufacturer in New York recently received an 

 order which read : " Please send me one pair of thin rubber 

 gloves for a lady weighing about 130 pounds," and being a 

 conscientious merchant, he at once set about getting vital sta- 

 tistics. Figuring that a 130 pound female of large frame, who 

 was thin, and who daily manipulated a rubbing board, would 

 possess an 8)^ hand, and that a small-boned, petite, plump in- 

 dividual of the same weight, whose exercise was confined to 

 holding a lorgnette, would have a I'/i hand, he split the differ- 

 ence and sent a pair of 7 and was right the first time. 



