676 



occupies an intermediate place. Moreover, tlie rather complicated 

 properties of tiie latex may be understood, if we bear in mind, 

 that it is a vegetable juice, in which t)esides the rubber-carbo- 

 h}'drate8, also proteins, resins and other colloids play a part, and 

 in whicli eacii in its turn may come to tiie (Vont. 



The composition of Hevea latex is not constant. The quantity of 

 rubber and the quantity of secondary constituents depend on several 

 factors, which cause changes in the physiological condition of the 

 tree; moreover the tapping-system has a great influence. Besides we 

 have to bear in mind, that aftei- tapping the acidety of latex prin- 

 ci[)ally by bacteriological transformations, increases, even to such 

 an extent, that after twelve hours "spontaneous" coagulation sets in. 



If, however, circumstances are carefully chosen, it is an easy 

 matter, to get a regular daily su|)ply of latex of a certain compo- 

 sition. For that purpose one has to be restricted to a certain group 

 of trees, from which, according to a certain tapping-system, latex 

 is gathered daily, which moreover is always treated in the same 

 way. The onlj remaining changeable factor, the meteorological 

 circumstances, are then immaterial, if one keeps separate the latex 

 of those days, on which in the morning the trunks were still wet, 

 after nocturnal lains, or on which the latex gets drenched by an 

 early shower. 



We could, by taking these precautions \'ery carefully, obtain 

 quite sufficiently constant results, in the coagulation-experiments to 

 be described here, with series of observations covering several weeks. 



If, however, later on, one reverts to such observations with latex 

 of a different group of trees, or a different tapping-system, the quanti- 

 tative data do not correspond exactly any more, though the general 

 course of the phenomena remains the same. In ^ 8 we intend to 

 give a few examples of the differences caused thereby, and also 

 of the influence of the gradually increasing acidity of the latex. 



The results to be discussed here, have therefore to be interpreted 

 in such a way, that the principal features of the view are generally 

 available, but that the limits of the different ranges may be moved 

 more or less, according to the composition of the latex with which 

 one operates. 



Against this drawback, that one operates with a non-constant, 

 and not arbitrarily reproducible material, we find, as a great ad- 

 vantage, the fact, that Hevea latex is mixable with water in any 

 proportion. So one may easily prepare all percentages of rubber 

 from the original percentage (30 — 40 7„) down to the lowest one, 

 and one may, without great difficulty, traverse and search systematic- 



