April, 1910.] 



29i 



GUMS; RESINS, SAPS AND EXUDATIONS* 



THE SCIENCE AND PRACTICE OP 

 PARA RUBBER CULTIVATION. 



By John Parkin, m.a., f.l.s. 



(Prom Science Progress, No- 15, 

 January, 1910.) 



Part I. 



Caoutchouc,* the elastic gum prepared 

 by the Indians of Tropical America from 

 the milky juice (latex) of certain trees, 

 became known in Europe during the 

 seventeenth century as a curiosity. It 

 remained so in England till the year 

 1770, when Priestly recommended its 

 fitness for erasing lead- pencil marks, 

 hence the origin of the name "India- 

 rubber," now often shortened to "rub- 

 ber," 



This substance first assumed commer- 

 cial importance about the year 1823 

 through the method of waterproofing 

 patented by Macintosh. Its uses be- 

 came greatly extended later by the dis- 

 covery of vulcanisation, a process in- 

 vented by Goodyear in America in 1839, 

 and independently by Hancock in Eng- 

 land about the same period. These 

 pioneers showed that when caoutchouc 

 is intimately mixed with sulphur and 

 subjected to a temperature of about 

 150°C, its elasticity is not only increased 

 but remains piactically uniform through 

 a wide range of temperature; further, 

 its durability is greatly prolonged. Raw 

 caoutchouc, on the other hand, softens 

 with an increase and hardens with a 

 decrease of temperature. Without the 

 discovery of vulcanisation india-rubber 

 would have remained of quite minor 

 importance ; very little unvulcanised 

 rubber is now used in manufacture. The 

 demand for raw rubber from this time 

 onwards steadily rose. New uses for it 

 were continually being found, and finally 

 the incoming of the rubber tyre, espe- 

 cially the pneumatic variety, has caused 

 an ever-growing demand. 



The great basin of the Amazon has 

 always supplied the largest quantity, as 

 well as the finest quality, of this now 

 indispensable raw material. This caout- 

 chouc, known in commerce as " Para," 

 after the Amazon port of that name, 

 ha9 been the recognised standard for 

 fully half a century. It is obtained 

 from the euphorbiaceous tree, Hevta 

 bratsilienfiis, otherwise known as the 



* The word "caoutchouc" is a corruption of 

 the native name for this substance. 



Para-rubber tree. Though this is the 

 most important rubber tree, yet several 

 other laticiferous plants furnish commer- 

 cial caoutchouc- notably among these 

 may be mentioned : Manikoi Glaziovii 

 (Ceara rubber) of Eastern Brazil ; Castil- 

 loa elastica, of Mexico and Central 

 America ; Funtumia elastica (Lagos rub- 

 ber), and species of Landolphia of 

 tropical Africa ; Ficus elastica (Ram- 

 bong) of Assam and Malaya, the familiar 

 " rubber plant" of our greenhouses. At 

 the present time Brazil furnishes about 

 00 per cent, and Africa 30 per cent, of 

 the world's supply. 



The consumption of India rubber has 

 augumented so rapidly within the last 

 few years, owing largely to the great 

 increase in rubber-tyred vehicles of all 

 kinds, that the supplies are becoming 

 quite unequal to the demand. Hitherto 

 the world's crop of rubber has come 

 solely from wild sources. In all prob- 

 ability if the cultivation of caoutchouc- 

 yielding trees had been delayed much 

 longer, a rubber famine would be immi- 

 nent. As it is, there will be a shortage 

 in supplies for a few years to come. 

 Prices for the raw material will rule 

 high, and rubber goods will tend to 

 become dearer or of lower quality 

 through admixtures. The extended use 

 of caoutchouc will be prevented, and 

 its much-needed employment for floor- 

 ing and pavement, where wear and 

 tear is great or silence desired, will 

 have to be postponed. The manufac- 

 turers are now paying an unprecedented 

 and quite unforeseen price for this raw 

 material. Pine hard Para is at present 

 quoted in the London market at about 

 7s, d. per lb. * A year ago it was only 

 5.s.;infact it is now nearly double the 

 average figures for the twenty-five 

 years preceding 1909. In July, 1909, the 

 price rose sensationally from 0s. to 8s. 

 per lb. It was generally expected that 

 it would drop considerably in the 

 autumn with the incoming of the 

 Amazon supplies. These, however, 

 turned out to be smaller than anti- 

 cipated, and instead of a fall, a rise of 

 another shilling per lb. took place.t At 

 present there seems to be a probability of 

 a 7s. basis instead of a 5s. one being 

 maintained for some time. The soone>* 

 the price can be brought down to 4s. or 

 5s, per lb. the better for the progress of 

 the world generally. 



* London price 7.?, Gj<?., December 24, 1909. 



f The record figure, 9s. 2£d. was reached in early 

 November, 1909. 



