July 1, 1912.] 



THE INDIA RUBBER WORLD 



475 



Rubber Investigation at Berlin. 



WHILE largely devoted to the results of the investigations 

 of Dr. Ediiard Marckwald, during his recent visit to the 

 German possessions in Africa, dealt with in the March 

 and May issues of the India Rubber World (pages 269 and 425), 

 the annual report of the Berlin "Kautschuk Zentralstelle fiir die 

 Kolonien" likewise deals with the work of his colleague, Dr. 

 Fritz Frank, in that connection at their joint laboratory. 



A number of important .conclusions, founded upon the experi- 

 mental work carried out during the year ending in April last, are 

 recorded in detail. The institution was enlarged through the 

 valuable addition of a distilling plant, adapted for practical 

 demonstrations of the industrial utilization of German colonial 

 rosin and other products ; another new feature being the installa- 

 tion (now in progress) of a new experimental washing plant, 

 constructed on "rational" principles. This plant will, it is 

 claimed, be all the more appreciated, as the process used does not 

 in any way injure the rubber treated; the washing of experi- 

 mental quantities up to one ton having been provided for. 



RUBBERS TESTED. 



The rubber samples tested were 185 in number: Manihot, 77; 

 Kickxia, 69; CastiUoa, 9; Fictis, Landolphia, etc., 16; Hevea, 14. 

 MANIHOT. 



Two samples lately received from Togo were found of par- 

 ticularlygood quality, showing a marked improvement over that 

 of samples received last year from the same plantation. This 

 improvement is solely attributed to the rational manner in which 

 the operation of the plantation has been conducted. 



A number of samples of Manihot rubber from an East-African 

 plantation were tested, wliich had all been coagulated by chloride 

 of calcium. While it had not been found possible to remove the 

 chloride of calcium, the unfavorable effects apprehended from the 

 use of that coagulant were not noticed. Still caution is recom- 

 mended in its employment. 



With respect to washing, the report states that all the washed 

 samples tested had materially suffered through that process ; 

 while those which had been subjected to a supplementary heating 

 were completely spoiled. In fact no rubber washed in the colony 

 could be regarded as a high-grade article. 



During his recent visit to East .\frica. Dr. Marckwald collected 

 a number of samples of rubber extracted and prepared by the 

 most varied methods, respecting which a comprehensive report is 

 in preparation. 



KICKXIA. 



A number of samples of Kickxia from a West-African planta- 

 tion, showed in the case of those prepared with Purub, marked 

 appearances of decomposition. Hence, the necessity becomes 

 more and more evident of not adopting general methods of coagu- 

 lation, but of using a system adapted to the soil conditions and 

 to the salts which are thus contained in the latex. 



Coagulation with tannin has been partially adopted, yet the 

 rubber thus obtained has an unattractive, opaque appearance; not 

 realizing a good price. 



A number of Kickxia samples were investigated, which had 

 been prepared by the introduction of carbonic acid and the blow- 

 ing in of air. The report says on this subject: 



"It was demonstrated by testing, that the carbonic acid process 



is not practicable for Kickxia latex ; an observation which was 



also confirmed through the investigations of Dr. Marckwald in 



East .'\frica, and must likewise be extended to Manihot latex." 



CASTILLOA, FICUS, HEVEA, ETC. 



Regarding above samples, special approval is expressed of 

 Hevea, which, it is remarked, with favorable soil and the right 

 preparation, will yield rubber of a thoroughly first-class character. 



The CastiUoa samples were relatively good, but, it is added, the 

 cultivation of this variety is hardly to be recommended, on ac- 

 count of its requirements and its only yielding third-rate qualities. 



RUBBER FROM BARK. 



Among other points which have reached a technical solution, is 

 the question of the extraction of rubber from the barks of trees ; 

 thus utilizing a sub-product. On the other hand, the trials made 

 as to the profit attending the operation have not yet been con- 

 clusive. Kickxia bark yielded about 3.5 per cent, of wet rubber, 

 while Manihot bark yielded about 2 per cent, of rubber. The 

 report estimates, however, that the barks actually contain about 

 double the above-named quantities of rubber. 



The rubber thus obtained was of satisfactory quality and could 

 be successfully vulcanized. The work was carried on in two 

 directions : 



1. Finding whether by working up large quantities at the same 

 time, it was possible to reduce the consumption of power. 



2. Finding whether the yields could be increased by working 

 up fresh material. 



As illustrating tlie principle involved in the last-named prob- 

 lem, it is remarked that in the working up of gutta percha leaves 

 and bits of wood, relatively large quantities of gutta percha were 

 extracted from fresh material, while there was little or no yield 

 from dry material. Similar results attended experiments with 

 parts of gutta percha plants from New Guinea. These investi- 

 gations are being continued. 



FERTILIZING. 



Working from both ends of the line of investigation, the com- 

 position of the ashes of crude rubber has a special connection with 

 the quality. This composition is directly dependent upon the soil 

 of the plantations. As the report remarks, lime and magnesia 

 salts, as well as phosphates, exercise a different, but in all cases 

 important, effect upon the rubber to be obtained. Experiments 

 in East Africa personally conducted by Dr. Marckwald, and since 

 his return, followed up by Professor Zimmermann, will be fully 

 dealt with in the next quarterly report of the "Zentralstelle." 



One important feature of these new investigations is based on 

 the fact that the absence of certain salts in the soil has been 

 found to lead to the production of inferior qualities of rubber, 

 notably in the case of Hevea. As to how far it is possible to 

 supply these salts artificially by fertilization, is a subject on which 

 the "Zentralstelle" is now working. 



VISCOSITY OF RUBBER. 



Prominent among the subjects of physical tests, were those as 

 to the viscosity of rubber; the necessary apparatus having been 

 to a great extent reconstructed. In this connection, it is re- 

 marked that viscosity gives extremely valuable indications as to 

 the quality of rubber and as to the durability of the articles which 

 may be made from it. Yet it is added, it does not give any values 

 of general application, but only of a comparative nature. 



OIL FROM KICKXIA SEEDS. 

 Seeing the preponderating importance of Kickxia in Kamerun, 

 the question of the extraction of oil from its seeds is of consid- 

 erable importance to German rubber-growing interests. The 

 opinion is expressed that the profitable utilization of the seed 

 depends upon the removal of the bitterness noticeable in the oil- 

 cakes, in order to be able to use them as feed. It will be neces- 

 sary in the first place to elucidate the chemistry of the bitter 

 substance present. If this is not successful, then the whole of 

 the oil must be obtained by pressing under heat, or otherwise 

 extracted and used for technical purposes. 



