In order to prevent decomposition of any proteid impurity which may remain incorporated with the rubber, the freshly coagulated rubber is sometimes cured in the smoke of burning wood or a small quantity of an antiseptic such as creosote is added during coagulation.
Pernambuco rubber, as is the case with most rubbers coagulated by saline solutions, contains a large quantity of water.
It is then coagulated by the addition of an acid liquid, acetic acid or lime juice being generally employed, and the mixture allowed to stand.
The mucins and mucoids belong to this group; they are acid and contain no phosphorus; they give the albumin colour reactions but are not coagulated by heat.
Both these soluble hydrates are readily coagulated by traces of a salt, acid or alkali; Crum's hydrate does not combine with dye-stuffs, neither is it soluble in excess of acid, while Graham's compound readily forms lakes, and readily dissolves when coagulated in acids.
Albumins (as classified above) are soluble in water, dilute acids and alkalies, and in saturated neutral salt solutions; they are coagulated by heat.
When coagulated in water, the mass is placed in vats in the ground and allowed to dry, this taking place in about a fortnight.
The Hevea product is obtained annually by tapping the trees and coagulating the sap over a smoky fire, but the caucho is procured by felling the tree and collecting the sap in a hollow in the ground where it is coagulated by stirring in a mixture of soap and the juice of a plant called vetilla.
The trees are regularly tapped and the coagulated latex which exudes is collected and worked up into rubber.
A bubo is found to consist of a chain of enlarged glands, surrounded by a mass of engorged connective tissue, coagulated blood and serum.