Vol. X. No. 242. 



THE AGRICULTUKAL NEWS. 



2.51 



TACKINESS IN RUBBER. 



An interesting article under this title appears in the 

 India-Rubber Joarnal for May 20, 1911. It describes 

 tackiness, in the mild form, as showing itself as a sticky 

 appearance on the surface of the rubber; in its more serious 

 shape, tackiness may exist to such an extent as to cause the 

 rubber to become a syrupy liquid which can only be used 

 (under the name of heated rubber) as a by-product. The 

 agents responsible for tackiness have been considered to be: 

 (1) Ijacteria, (2) sunlight, (.3) heat, (4) chemical substances. 

 Attention is drawn to the fact that when observations 

 on tackiness were first made in Ceylon, it was considered to 

 be due almost entirely to growths of bacteria on the surface 

 of the rubber. It was therefore suggested that specimens of 

 rubber showing tackiness should be isolated, and it has 

 been claimed that the adoption of this jireventive measure 

 has resulted in a reduction in tackiness. It is admitted that 

 some cases are largely, if not entirely, due to the action 

 of bacteria, in rubbers containing high percentages nf 

 proteids. Such rubber is usually the first obtained from 

 old trees, or that from young trees, and it is interesting 

 that these kinds .show the greatest tendency to undergo 

 putrefactive changes. Another matter is that tacky rubber, 

 when analysed, is usually found to contain a high propor- 

 tion of proteids. Support is given to the idea that bacteria 

 plaj' a part in tackiness by the fact that the condition can 

 spread by contact, and that smoked rubber does not frec^uently 

 become tacky — probably because of the action of antiseptic 

 substances in the smoke. These conditions, make it obvious 

 as to what should be done to minimize the chances of rubber 

 becoming tacky through bacterial action. 



Tackiness is sometimes found to develop more cjuickly 

 under the intiuence of sunlight: although the true explanatic^n 

 of the action is not known. It is very irregular, for .samples 

 of rubber have been kept in sunlight for some years without 

 becoming tacky. In any case, there is a greater recognition 

 of the importance of sunlight in the matter, in the fact that 

 many factories are using ruby- or orange-coloured glass, in 

 order to e.xclude the chemical rays of light. 



As regards heat and tackiness, it is well recognized that 

 when rubber is exposed to high temperatures, it becomes soft 

 and sticky; this is why it is usually dried at a maximum 

 temperature of 90° to 100° F. It is the case, however, that 

 heat alone may not produce tackiness, for if putrefaction is 

 prevented, the heated rubber will cool to a product having 

 the ordinary consistency. Heat is most likely to produce 

 tackiness when the rubber is warmed in an atmosphere rich 

 in organic matter. 



Chemical agents apparently cause tackiness directly, 

 much in the same way as this is done by sunlight. Bamber 

 states that enzymes may be resjionsible for the condition; 

 though this view has been given little support, and is cpies- 

 tioned by Spence, who has .shown that coagulants like sulphuric 

 acid have a strong effect. Similar results have been obtained 

 by Brindejonc, by using weak solutions of acids, for instance 

 acetic acid, which may be produced by bacteria. It is 

 interesting that carbolic acid acts in a similar way, 

 indicating that the action of bacteria is indirect in its 

 nature. Similar results have been obtained by soaking the 

 rubber in salt .solution. 



A purely hypothetical explanation of tackiness is that of 

 Frank, who attributes it to the presence of imperfectly poly- 

 merized portions of the rubber, which are originated through 

 incomplete mixture of the coagulant with the latex. It is 

 seen that all the above matters have to deal with the causes 

 of tackiness. The chemical explanation of its production has 

 not yet been found, and careful work requires to be done 

 before this can be provided adequately. 



AGRICULTURE IN SOUTHERN NIGERIA. 



AGKKJULTUKE. In 1907, the value of the exports of 

 cotton, maize and cacao was £184,342, and in 1908, £161,658. 

 In 1909, in spite of the comparative failure of maize, the 

 total increased to £220,927. 



c.^cAO. The area of land under cacao is increasing 

 rapidly, and will probably continue to do so. The shipments 

 under this head have been: 190.5, 1,057,987 It..; 1906, 

 1,619,987 ft.: 1907, 2,u89,225 ft.; 1908, 3,060,609 ft.; and 

 1909, 5,019,150 ft. 



t'OTTON. In 1908, there were shipped from Southern 

 Nigeria: cotton lint, 2,294,356 ft.; cotton seed, 5,591,979 ft. 

 In 1909, cotton lint, 5 032,916 ft.; cotton seed, 10,756,777 ft. 



MAIZE. In 1909, over 5,000 tons less maize were shipped 

 than in 1908. 



GROUND NUTS. In spite of the introduction of new seed, 

 and the help given by instructors from the Gambia, the 

 Western Province exports little or no ground nuts, although 

 a good deal is planted, and sold in the markets for home 

 consumption. Such ground nuts as are now exported from 

 Southern Nigeria come from the Central Province and North- 

 ern Nigeria. 



ECOXOMic: GARDENS. A great number of plants, 

 including Para, fibres and fruit, were distributed from the 

 different gardens, as follows: Western Province, 36,000 plants; 

 Central Province, 67,434 plants; Eastern Province, 22,267 

 plants. In the Western Province, vanilla fruited for the 

 first time. 



ENT0M0L0(A'. The (Government Entomologist gave lec- 

 tures and issued reports, which have been much appreciated 

 by the more intelligent farmers, on the diseases attacking the 

 cacao and maize crops. 



COLLECTION OF PLANTS. Eighty-three floral and other 

 specimens were sent to Kew for identification, 



IMPEKIAL INSTITUTE. Many plant specimens of economic 

 value were sent to the Imperial Institute, and full reports of 

 these were published from time to time in the Bulletin of 

 that Institute. {Colonial Ee2>ort$ — Annual, No. 665, p. 13, 

 issued February 1911.) 



Information has been received from Mr. H. A. Tern- 

 pany, B.Sc, Superintendent of Agriculture for the Leeward 

 Islands, to the effect that, in the celebrations recently con- 

 ducted in Antigua in honour of the Coronation of His Majesty 

 King George V, the proceedings included a public tree- 

 planting ceremony, in which part was taken by His Excel- 

 lency the Governor, Members of Council, Heads of Govern- 

 ment Departments, and representatives of the children in the 

 elementary schools. 



In all, forty-five mahogany trees were planted to form 

 an avenue along a newly made road, which was declared 

 open by the Governor at the time, and is intended for con- 

 venience in leaving the city of St. John, in the direction of 

 Encilish Harbour. 



