47° The Ohio Naturalist. [Vol. XII, No. 4, 



The liquid is white, slightly acid and acrid odor. This liquid 

 failed to coagulate after addition of more acid. Slight excess of 

 alkali increased its viscosity, changed its color from white to 

 brownish \'ellow, but did not coagulate or precipitate it. Boiling 

 had no effect. Excess of acetone gave a finely divided precipitate 

 the particles of which were not cohesive. Evaporation of the 

 mixture, after washing with water and treatment with boiling 

 acetone, gave a small quantity of black, soft rubber, destitute of 

 strength. The cheese was composed of: 



Water 33.46% 



Rubber 3.99% 



Resin 62.95% 



Working up this cheese of the plant in the usual manner with 

 solvents, straining through gauze to remove dirt, evaporating, 

 with low heat, the excess of solvent adding an excess of precipitant, 

 washing the precipitant and dissipating the precipitating agent, 

 gave a good grade rubber. 



The rubber obtained in this manner is black, finii, not tacky, 

 odorless and strong. In qtiality it is much better than the product 

 obtained from its neighbor. Milkweed. The qualities of this 

 rubber confirm the old adage "that blood is thicker than water," 

 and proves a more apt one, "that Apocynaceous rubbers are good 

 rubbers." 



Milkweed latex, however, is richer in rubber than that of 

 Indian Hemp. The proportion of rubber in the entire plant 

 remains on the same ratio as the ainount of latex remains equal, 

 and in both cases is entirely too small to be profitable. Of the 

 total rubber present in the latex, 96% of it is won in the cheese 

 formed by the natural coagulation of the latex. Ninety-six 

 per cent of the total rubber found, ranks as Grade A, and four 

 per cent grades as C. 



The resin is mahogany red, transparent, medium hard, slight 

 characteristic odor and tasteless. 



During this investigation we have found that the soil condi- 

 tions under which the plant was grown, exerts an influence upon 

 the amount of rubber in the latex. Plants grown upon dry, 

 sandy soil of West Akron, gave a latex containing 2.27% rubber 

 and 20.69% resin. The latex of plants grown upon the wet swamps 

 of South Akron, contained 1.12% rtibber and 15.04% resin. 

 Rubber from dry grown plants is of better quality than that of 

 wet grown plants. 



Natural latex from dr}^ land Apocynum contains: 



Water 72.29% 



Solids 26.21% 



Ash 1.59% 



