1913] Hall-Goodspced: Chrysil 189 



report on the yield and the quality of the product. The samples of 

 shrub consisted of plants cut off a short distance below the surface of 

 the soil and with all growth of less than three j-ears removed ; in other 

 words, they consisted of those portions which would presumably be 

 utilized in commercial operations. Dr. Spence very kindly undertook 

 to make the examinations, and reports as follows regarding the prep- 

 aration of the rubber and its properties : 



In preparing the samples for analysis the woody ones were ground up on a 

 pair of corrugated rolls, or a " cracker, ' ' and the bark samples were ground up 

 and sheeted out on a smooth roll. It is interesting to note that the bark forms a 

 smooth sheet on the mill. 



.Each of the four samples was placed in a bottle, covered with 100% benzol and 

 shaken one hour. It was then allowed to stand twelve hours and the liquor drained 

 off. This washing was repeated twice. After allowing the small dirt to settle 

 out, the three combined washes were distilled to a small bulk, 400 to 500 cc. The 

 ruljber was coagulated from this concentrated solution by the addition of pure 

 methyl alcohol. The coagulated mass of rubber was kneaded in fresh methyl 

 alcohol and vacuum dried at 95 °C. The dried rubber is dark brown in color, has 

 very little tackiness and considerable elasticity. When the solvents are removed 

 by boiling in water, a very tacky rubber results. 



A larger sample of bark from both stems and branches was extracted and the 

 rubber obtained was compounded as follows : rubber 100 g., zinc oxide 100 g., ac- 

 celerator 3 g., sulfur 6 g. This compound was then divided into five portions and 

 these W'Cre vulcanized for thirty minutes, sixty minutes, ninety minutes, two hours, 

 and three hours, respectively. Forty pounds of pressure was applied in each case. 

 The sixty minute treatment under forty pounds was full cure. 



These samples* indicate that the rubber vulcanizes readily and gives a product 

 of a very fair quality. I have no hesitation in committing myself as to its value 

 as far as it is possible to estimate this from such small samples as I was able to ob- 

 tain. In order to report on the exact commercial value of this rubber it would be 

 necessary to make many more tests and much more exhaustive ones, but from the 

 small samples I sent you I can already safely say that the rubber is of high 

 grade and average quality. It is not as good as the best fine Para, but it is a 

 great deal better than most Africans or low grade rubbers. The results would 

 indicate that the bark of shrub No. 64 (that is viridiilus) might well be investi- 

 gated more extensively as a possible source of crude rubber existent in this country. 



IV. BOTANICAL CLASSIFICATION; THE NAMES OF THE 



PLANTS 



The plants in which rubber has been found during the course of 

 this investigation all belong to two closely related genera of the Com- 

 positae, namely Chrysothamnus and Haplopappus. The latter is 

 apparently of little importance, for although rubber has now been 



i The five samples referred to by Dr. Spence are in the form of circular discs 

 one-fourth inch thick by one and one-fourth inches in diameter. They are pre- 

 served in the Botanical Museum of the University of California. 



