March t, 1905.] 



THE INDIA RUBBER WORLD 



193 



THH TROUBLH WITH AFRICAN RUBBERS. 



HY J. W, C. 



TO THE Kditor of The India Rubher World : It occurs 

 to the writer that no satisfactory solution of the trouble 

 with African rubbers is likely to result from the discussion 

 now carried on in the columns of this Journal unless we cease 

 Ruessing and begin at the beginning. The •' beginning " takes 

 us back to the African jungle, to the banks of the Congo, to 

 the depths of the primeval forest. No one interested in the 

 rubber manufacturing industry has to be told of the crude 

 methods still followed in the securing of sap, and the almost 

 total destruction of trees and vines yielding it. over large and 

 steadily increasing areas in Africa. The change for the better 

 that is reported from the South American field seems to have 

 made little progress there. Then, too, the African country 

 seems to contain a greater variety of plants from which latex 

 is secured, and the product comes to market under a bewilder- 

 ing list of names, and each particular brand is individualized 

 by the method of its gathering, location, its color, shape, and 

 condition. Let us consider briefly a few of these: 



Senegal and Bissao balls, from Senegambia, Soudan, and 

 Bissagos islands, come in balls or sheets, outside surface black 

 or brown ; cut surface, rose color or white ; filled with sand, 

 bark and dirt. Loss in working 25 to 50 per cent. 



Gambia balls, from the same source, black or brownish 

 white; cut surface white or light rose color; filled with sand 

 and bark. Loss 20 to 50 per cent. 



Cisamance, (Boalam) from Casamance river table land, comes 

 in balls or sheets. Outer surface dark brown, cut surface, grey, 

 cream yellow and reddish ; filled with holes, sand and earth. 

 Loss 40 per cent.; odor bad. 



Niggers from Sierra Leone and Massai come in red, brown, 

 or white balls; cut surface showing much the same color. 

 Sometimes filled with earth and bark ; sometimes quite clean. 

 Loss 10 to 35 per cent. 



Liberia comes in white, brown and black balls and lumps; 

 cut surface of balls rose color and while ; of lumps, green, yel- 

 low, and white. Quite clean as a rule. Odor of lumps very 

 bad. General loss 20 to 40 per cent. 



Accra, from the Gold Coast, comes brown or black, and cut 

 surface shows yellow and brown ; sometimes quite dirty. Loss 

 30 to 45 per cent. 



Gaboon balls, from the French Congo, come in large and 

 small balls, black orgrey. Cut surface of large balls shows rose, 

 blue, red ; of the small, grey, white, or green. Contains bark 

 and sand ; odor bad. Loss 30 to 40 per cent. 



Kasai rouge, from the Congo Free State, comes in small balls, 

 color red. quite free from impurities. Loss 6 to 8 per cent. 



Kasai noir, comes in pieces of irregular size formed of balls 

 stuck together. Contains little sand or wood, but on the other 

 hand is noticeable on account of quantities of volatile, ferment- 

 ing substances. 



Upper Congo (common) comes in balls, containing some 

 bark and water. Loss 15 per cent. Upper Congo (white) comes 

 in balls, and is very pure. 



Equateur, from the Congo, CDmes in balls stuck together 

 quite free from dirt. 



Lopori, from the Congo, comes in balls, and contains volatile 

 and fermenting substances. 



Aruwimi, Mongala, and Bumba come from Congo in large 

 balls, contain large quantities of fermenting substances, show 

 great loss in working, and are distinguished by a very bad odor. 



This is certainly enough to make the average superintendent 

 old before his time, unless he has the assistance of a chemist, 



and he. doubtless, could write books regarding that" tired feel- 

 ing," induced by each purchase of " Africans." With Para he 

 may, ordinarily, feel firm ground under his feet. The "personal 

 intelligence system" has made some headway there, with en- 

 couraging results. Knowing that the laiex contains substances 

 liable to fermentation, the best known preventive is used, viz. : 

 repeated action of moderate heat, to remove water and smoke 

 producing carbon, which acts as an antiseptic, and possibly as- 

 sists in the absorption of oxidized resin In the sap. 



In Africa, on the other hand, the quantities of dirt, sand, and 

 bark, in the gum marketed, tell the story of shiftlessness in 

 gathering, and the putrid odor, and general condition of lack 

 of intelligence or indilTerence in coagulating. In the Congo 

 country the gatherer may smear the latex over his entire body, 

 or upon his arm, as it exudes from vine or tree, or it may be al- 

 lowed to drip upon the ground from which it is gathered with 

 its accumulation of dirt and bark. Such a person will not be 

 overscrupulous regarding what he gathers. The fact that the 

 latex in the heart of the Landolphia is acrid, watery, and spoils 

 quickly is a matter of indifference. It goes into his gourd or 

 pail along with the rest. 



In the matter of coagulation there seems to be a correspond- 

 ing lack of intelligent direction. Brannt says that on the 

 Congo " fresh sap is mixed with four or five times its quantity 

 of water, upon which the rubber rises like cream, in a mass 

 containing substances sure to result in fermentation, and de- 

 terioration." This shows the origin of one trouble to which 

 Mr. Thornton has referred. 



In Pernambuco, however, a solution of potash combined 

 with alum is used to coagulate. Gum treated in this way loses 

 its elasticity, becomes brittle, and the chemist will discover 

 that the crystals on the surface are alum. In Madagascar and 

 Gambia citric acid and sulphuric acid are used; in the Ivory 

 Coast and Kamerun districts, sea or common salt. The use 

 of salt to coagulate will frequently account for the large per- 

 centages of water in African rubbers. It appears, therefore, 

 that the most satisfactory results are obtained by the use of 

 smoke, artificial or natural heat, or salt, in coagulation, and 

 that the use of alum, mineral or vegetable acids, and the addi- 

 tion of water will result in injury to the quality, if it does not 

 altogether destroy the rubber. 



This condition apparently emphasizes the necessity for chem- 

 ical examination of all rubber before it is used in the factory. 

 The " by-guess and by-gad " method relied upon with such 

 confidence by some superintendents can hardly fail of disas- 

 trous results. If the chemist can tell whether acid was used in 

 coagulation, so he can ascertain the percentages of resins, oxy- 

 gen, etc. Mr. C. O. Weber, the eminent expert, directs special 

 attention to the presence of resins: " Resinous impurities de- 

 termine to a considerable degree the behavior, especially of the 

 inferior brands, of India-rubber in practical working, and they 

 are also supposed to have a marked influence upon the stabil- 

 ity of the finished product." 



Consequently it follows that the superintendent who from in- 

 difference, or lack of facilities, fails to ascertain the quantity of 

 sulphur that will be absorbed by resinous substances in the 

 gum used, and in consequence, diverted from the proper vul- 

 canization of a given compound, must not be surprised if goods 

 fail to cure properly. 



That the presence of resinous matter in rubber is something 

 to be reckoned with, and dealt with intelligently, is shown in 

 this table, compiled from the experience of several authorities : 



Para 2 % Kasai 4 % 



Congo 8,5,* Lagos 45? 



Gambia. 7.5 ^ Lopori 3 ;* 



