222 



University of California PuhIicatio)is in Tioianij [Vol. 7 



T.\BLE :i. — (Continued) 



Species 

 149 Haplopappus cricoides 



215 C. n. gnaphalodes 



227 C. n. consimilis 



229 C. n. speciosus 



.Acetone 

 Extract 

 VcT cent. 



9.17 



7.88 



7.47 

 5.53 



4.29 

 4.29 



98 

 30 



3 . 55 

 4.83 

 4.72 



Henzene 

 Extract 

 Per cent. 



3.92 



2.48 



3 11 

 2 . 50 



2.57 

 1.92 



2.14 

 2 12 



2.49 

 2.37 

 2,07 



Remarks 



C"offoo mill. 

 Pohhlf mill. 



Coffee mill. 

 Pebble mill. 



Coffee mill. 

 Pebble mill. 



Coffee mill. 

 Pebble mill. 



Coffee mill. 

 Pebble mill. 



4 hours. 



4 hours. 



4 hours. 



4 hours. 



G hours. 



Pebble mill (Food & Drug Lab.) 



Although, as in all such cases, a far larger number of analyses is 

 necessary to give entirely reliable evidence it appears from the figures 

 given above that the product of the pebble mill, irrespective of the 

 fact that some rubber is kept behind on the pebbles, yields approxi- 

 mately as large an amount of rubber as does the product of the coffee 

 mill. The results given in the following table leave no room for doubt 

 that rubber does adhere to the pebbles. 



Table 4. — Evidence that Eubber Adheres to the Pebble.s avhen Material is 



Ground in a Pebble Mill 



Species 



206 Haplopappus nanus 



Tn view of these results the conclusion seems inevitable that the 

 degree of fineness of the ground material is an important factor in 

 the extraction of rubber from non-latex rubber-bearing plants accord- 

 ing to our method of chemical analysis. Apparently the added 

 fineness of the product of the pebble mill facilitates the thorough 

 extraction of the rubber to such an extent that the amount of rubber 

 added by this more nearh^ complete extraction compensates for the 

 amount retained upon the pebbles. In other words if over 2 per cent 

 of ni])])er is lidd on the pebbles, as is indicated by the results given 

 in table 4. one might expect that the benzene extract from pebble mill 

 mati'i-iiil would lie approxinuitcly 2 per cent less than that from coifee 



