70 CENTRAL AMERICAN RUBBER TREE. 



Dr. Weber do not mean that a final and satisfactory conclusion 

 has been reached. Dr. Weber finds that by the simple expedient 

 of diluting the fresh latex of Castilla with live times its volume of 

 boiling water and adding 8 ounces of formaldehyde to each barrel of 

 the resulting fluid, all the impurities to which the inferiority of Cas- 

 tilla rubber are due can be removed, since they will remain in solution, 

 while after twenty-four hours the clean rubber will be found in a 

 "snow-white cake" which can be lifted off the top. Dr. Weber con- 

 tends that rubber prepared in this way is "absolutely free from solid 

 impurities of any description, * * * either soluble or insoluble, 

 organic or inorganic,'' and that it is equal or superior to the finest 

 brands of Para rubber. The process is simple and inexpensive, 

 and if the mechanical qualities of the rubber meet Dr. Weber's 

 expectations when the practical tests of manufacturing have been 

 applied, it would seem that the essential requirements of the problem 

 have been met. and in any case valuable progress has been made. 

 It seems, moreover, from the investigations made by Parkin in Ceylon 

 that this method is capable of still further simplification. 



When the latex of Castilla is mixed with water and allowed to stand, in the course 

 of an hour or two the caoutchouc particles have all floated to the top in the form of 

 a thick cream. The diluted latex of Hevea, on the contrary, shows no signs of 

 creaming, even when submitted to a low temperature. The difference is most likely 

 due to the larger size of the caoutchouc globule in the case of Castilla as compared 

 with that of Hevea. « 



Parkin found, however, an interesting difference between the latex 

 of Castilla in Ceylon and that described from tropical America by 

 Biff en. in whose results Weber may be said to acquiesce, since he 

 holds that the albumens of Castilla latex are readily coagulated by 

 alkaline solutions. 



The proteid of the latex of Castilla elastica has also been investigated to some extent 

 by Biffen. He found that the latex gives an acid reaction, and that on the addition 

 of a little alkali it is coagulated. This he considered to be due to the nature of the 

 proteid which exists as acid albumen in the latex; on neutralization it comes out of 

 solution and gathers together the caoutchouc particles into clots. 



Now, the latex of the Castilla introduced into Ceylon | C. markhamiana) does not 

 behave like this. On the very gradual addition of alkali to the latex or to the fil- 

 trate (the liquid part of the latex without the globules of caoutchouc) no coagulation 

 or precipitation occurs. Alcohol causes a coagulation of the latex and a copious pre- 

 cipitate in the filtrate, which is quite soluble again in water. Proteid is present in 

 considerable quantity, about 4 per cent being indicated by analysis. Coagulation is 

 brought about neither by acids nor by boiling. Thus it looks as if the proteid belongs 

 to the class of albumoses. At any rate the type of Castilloa introduced into Ceylon 

 differs in this respect strikingly from that of the true Castilloa elastica examined by 

 Biffen. 



These facts are of interest, not only from their bearing upon coagu- 

 lation and function of latex, but because they indicate the extent to 



"Parkin, Annals of Botany. 14:198, 1900. 





