CHAPTER X. 



PHYSICAL AND CHEMICAL PROPERTIES OF LATEX. 



Colour — Consistency — Alkalinity — Sap exudations and acidity — 

 Caoutchouc globules — Object of producer — Mechanical impurities — 

 Analyses of the latex of Para rubber by Seeligmann, Faraday, Scott, 

 and Bamber — Variation in composition — Properties of caoutchouc 

 — Occurrences of resins and oily substances — Sugars — Proteids or 

 Albuminoids — Removal of proteids with formaldehyde and centri- 

 fugal separators — Mineral matter — Effect of temperature, ammonia, 

 formalin and acids on coagulation. 



The Physical Properties of Latex. 



THE latex of Hevea brasiliensis , as it flows from a freshly made 

 incision, is white or pale yellow in colour, and varies in consis- 

 tency mainly according to whether drought or rainy weather prevails. 

 It is slightly alkaline when fresh, and, as it flows from the tree, con- 

 sists of minute globules of caoutchouc and other bodies suspended 

 in a liquid containing various materials in solution and a varying pro- 

 portion of mechanical impurities. 



The latex obtained from the first incisions usually contains a 

 large proportion of sap exudations, which cannot be excluded as they 

 flow from the freshly-cut cortical cells ; they can be reduced by 

 incising instead of excising the laticiferous tubes. In several 

 instances the latex, by mixing with such exudations, becomes neutral, 

 and may rapidly develop acid properties. The conversion to an 

 acid state is followed by coagulation, and hence the first tappings 

 are frequently but unavoidably accompanied by a large proportion 

 of scrap. 



The object of the producer in the Tropics is to separate the glo- 

 bules of caoutchouc from the mechanical impurities and some of the 

 materials in solution, and it is necessary to explain clearly what 

 these substances are and their general characteristics. 



The planter, who aims at producing the highest quality of rub- 

 ber or perfecting the chemical and mechanical processes involved in 

 its manufacture from latex , must thoroughly grasp the nature of the 

 substances he has to deal with, and it is, therefore, necessary to enter 

 into a little detail. 



The mechanical impurities present in most samples of latex in 

 the field consist of pieces of bark, fibre, sand, &c, and they may be 

 easily separated by filtering the diluted solution through butter cloth 

 or fine gauze. 



