Chemistry: ,,The coayrilaüon of Hevea /nte.r". B\- Dr. 0. dk Vries. 

 (Communicated hv Prof'. P. van Romburgh). 



(Communicated at the meeting of January 27, 1923). 



I. Influence of the nii.ving-/)ro/)ortion of laten', /outer and acid, 



irregular series. 



It was known from previous investigations, tliat the coagulation 

 of Hevea latex witli acids siiows iii-egularities. Tlie obsei-vations 

 of several investigators, wiiicli we intend to discuss shortly in one 

 of tlie following paragraphs (^ 9), had only been made occasionally, 

 and did not give a sufficient insight into the phenomena; therefore 

 it seemed desirable to us to obtain a total view of the proportions, 

 by a systematical investigation into the complete range of mixing 

 of latex— water — acid. 



§ 1. The Latex. 



Hevea latex is a milky liqnid, which, under the microscope, 

 appears to consist of oval globules, ^ to 2 /t in size, and showing 

 a vivid Biownian movement; |)articles of less simi>le form occur 

 now and then. The fact, that one has not to deal with globular 

 particles, shows that latex is not a system liqnid: liquid, an emul- 

 sion in the sense of Wo. Ostwai.d's classification. On the other 

 hand, one should not speak of liquid: solid (suspension); the pro- 

 perties of the coagulniri obtaineil under various circnmstances, make 

 it probable that the rubber-particles in latex have a buttery consist- 

 ency, i.e. between liquid and solid. If we have to look upon this 

 as a more or less liquid nucleus, enclosed in a more solid super- 

 ficial skin, as some investigators assume, is a matter we do not 

 intend to discuss here. If we apply Freundmch's classification of the 

 colloids to latex, then undoubtedly it is a lyopliilic colloid, as shown 

 by the hydrous voluminous gel, obtained on coagulation, and by 

 the behaviour of the latex with regard to dehydrating and salting-out 

 substances; on the other hand, the hydrating power of the rubber- 

 globules is decidedly only limited, and the latex, as regards its 

 behavioui' towards mono- bi- and trivalent anions, is strongly remini- 

 scent of lyophabic colloids. So in this classification as well, latex 



