Ill 



article is on the market by the name of "Purub," and is 

 at present fairly widely advertised in the trade journals. 

 The main and effective substance in it appears to be hydro- 

 fluoric acid, which is well known from its application in 

 etching glass. 



The germs of putrefaction (tackiness) are always pre- 

 sent in latex, and the proteids therein offer them a suitable 

 feeding ground. Various measures may be taken ta prevent 

 putrefaction. In the smoking process the strongly anti- 

 septic smoke kills the germs, while the acetic acid which it 

 contains at the same time coagulates the latex. Smoke is 

 effective because owing to the way it is applied it acts on a 

 very thin layer of latex and therefore penetrates every part 

 of it. The putrefactive organisms being killed there is no 

 reason to withdraw the entire moisture. In the other 

 methods employed if moisture is present, even when in the 

 interior and shut off from the air, heating easily occurs 

 during transport encouraging the putrefactive germs to 

 develop. Hence rubber prepared by acetic or other acid 

 coagulators must have practically all its moisture extracted 

 if it is to go on to the market free from "tackiness." It 

 has been shown recently that well dried rubber is not so 

 good as that containing moisture. By the Purub method 

 it is immaterial, as far as preservation of the rubber is con- 

 cerned, how much moisture is left behind. 



Sandmann was led to experiment with fluorine com- 

 pounds in coagulating rubber latex by his experiences in 

 other fields. Thus it has been found that fluorine com- 

 pounds possess the property of killing putrefactive 

 germs, but affect yeast considerably less. On this account 

 they have for a long time been used in the distilling and 

 fruit-preserving industry. A very small quantity of hydro- 

 fluoric acid added to fruit juice keeps its fresh and pre- 

 serves its aroma for years. 



Coagulation with the fluorine compound is most simple. 

 The freshly collected latex, pure or mixed with water, is 

 strained through a cloth to remove foreign bodies into not 

 too large pans; the liquid fluorine preparation added and 

 thoroughly mixed by stirring. It is left for a few hours, 

 after which the coagulated rubber, which in the meantime 

 comes to the top, is removed, freed from water by pressure, 

 and is then ready for shipping. 



The fluorine which, as is well known, does not attack 

 rubber, is used in such a small quantity that it is totally 

 removed by water. In removing the water by pressing it 



