701 



4. Acetic, acid. Eaton again iiietitioiis a few series witli undiluted 

 and diluted latices, in which for the diluted latices the pappy, ('kinny 

 or liquid range was reached at acidities, corresponding fairlj well 

 with those found by us. For this acid Whitby does not give any 

 quantitative data, but only says that the first range of coagu- 

 lation is much wider than with the previous acids, and that, after 

 that, liquid mixtures are reached. With 30 '/u latex we did not find 

 any liquid mixtures ;top at 25 '/„ latex), but probably Whitby's 

 mixture had come, by the addition of diluted acetic acid, to a lower 

 percentage of rubber. Whitby did not find an upper limit of the 

 liquid range, as could not be the case (see P^ig. 5) on dilution of 

 30 7o latex with acetic acid of less than 50 7o- 



As we see, the data of both these investigations tit in a satis- 

 factory way in the frame of our recapilnlatingfigures and their 

 observations, partly seeming confused, are explained by the system 

 of ranges, as they have become known to ns at present. 



S U M M A R Y. 



Mixtures of Hevea Latex and water show, on addition of acids, 

 the phenomenon of the irregular series. For hydrochloric acid, nitric 

 acid, sulphuric acid and acetic acid the limits of the ranges (first 

 and second liquid range, first and second range of coagulation, stiips 

 of transition) were completely fixed for all mixing-proportions of 

 latex, water and acid (see fig. 1 — 5), and a comparison was made 

 between the position of the limits for these four acids. 



Buitemorg, December 1922. 



