1919] llall-Ooodspced : Chrusil 217 



the finely divided sample, especially as the bottom of tlie condenser 

 pressed down on this cotton plug during the course of the extraction. 



In almost all cases the first of the acetone-soluble substances ex- 

 tracted were strongly colored and turned the solvent a dark greenish 

 brown as soon as the extraction commenced. Thereafter the liquid 

 passing through the siphon tube was practically colorless. The benzene 

 extract was in practically all cases entirely without color. The acetone 

 extract after drying was very dark brown in color and strongly 

 odorous. The benzene extract when dry was on the other hand 

 colored light brown or yellowish, was almost entirely odorless, and 

 was distinctly rubber-like in consistency. 



There are, of course, a variety of other methods of analysis whicli 

 might possibly- have successfully replaced the one wliieli we have 

 employed throughout. For the sake of comparison we made trial of 

 another method, according to which the sample is first cxtraetrd 

 thoroughly with gasoline, then treated with strong sodium liydroxide, 

 then filtered, and the residue, finally, extracted with carbon tetra- 

 chloride. This method is far more time-consuming than llie one which 

 we have used and appeared to offer no real advantages as compared 

 with it. In the extraction of Guaj'ule shrul) on a large scale gasoline 

 is sometimes used as the solvent and acetone as a precipitant. The 

 recover^' of these reagents used in large (juantity in such a process 

 is a complicated problem l)ut it can be accomplished with very slight 

 losses. Moisture determinations were made in most cases. 



Tlic following table indicates something as to the relative accuracy 

 of our chemical analyses. Duplicate or triplicate analyses were often 

 run ill cases where comparisons were to be made with analyses of other 

 parts of the same plant or with equivalent portions of a given indi- 

 vidual collected on various different dates. The figures given are 

 selected as being representative. They indicate a relative degree of 

 accuracy for our analyses, sufficient at least to give an estimate of 

 the average amount of rubber contained in tlu; various species witli 

 which we have been concerned. 



