Gutta-percha, natural latex obtained from Palaquium gutta and several other evergreen trees of East Asia. The latex, collected by felling or girdling the tree, is allowed to coagulate and is t...

Blood clotting, process by which the blood coagulates to form solid masses, or clots. In minor injuries, small oval bodies called platelets, or thrombocytes, tend to collect and form plugs in ...

Caoutchouc, natural rubber obtained as a latex from various tropical plants, e.g., the Pará rubber tree. It is much more elastic than balata or gutta-percha. It is the most familiar and widely...

Ferric sulfate or iron (III) sulfate, chemical compound, Fe2(SO4)3, a yellow rhombic crystalline hygroscopic water-soluble salt that decomposes when heated to a temperature of 480°C. The ennea...

Zinc sulfate, chemical compound ZnSO4, a very water soluble, transparent, colorless, crystalline compound. It is commonly used as the heptahydrate, ZnSO4·7H2O, and is commonly called white vit...

Venom or zootoxin, any of a variety of poisonous substances produced by animals. In poisonous snakes, venom is secreted in two poison glands, one on each side of the upper jaw, and enters the ...

Astringent, substance that shrinks body tissues. Astringent medicines cause shrinkage of mucous membranes or exposed tissues and are often used internally to check discharge of serum or mucous...

Formic acid or methanoic acid, HCO2H, a colorless, corrosive liquid with a sharp odor; it boils at 100.7°C and solidifies at 8.4°C. It has the lowest molecular weight and is the simplest of th...

Viscose process, method widely used for the commercial preparation of rayon. Cellulose, prepared from either wood pulp or, less commonly, cotton linters, is treated with sodium hydroxide (an a...

Pará rubber tree, large tree (Hevea brasiliensis) of the family Euphorbiaceae (spurge family), native to tropical South America and the source of the greatest amount and finest quality of natu...