The composition of latex and of typical rubbers is given below:
The latex of the best rubber plants furnishes from 20 to 50% of rubber.
As the removal of the impurities of the latex is one of the essential points to be aimed at, it was thought that the use of a centrifugal machine to separate the caoutchouc as a cream from the watery part of the latex would prove to be a satisfactory process.
In Nicaragua the latex is collected in April, when the old leaves begin to fall and the new ones are appearing, during which time the latex is richest.
The watery portion of the latex soaks into the trunk, and the soft spongy rubber which remains is kneaded and pressed into lumps or balls.
There is no feasible method at present known of preventing the inclusion of the resin of the latex with the rubber during coagulation, and although the separation of the resin from the solid caoutchouc by means of solvents is possible, it is not practicable or profitable commercially.
They possess a delicate Laticiferous layer of protoplasm, with numerous small nuclei lining Tissue the walls, while the interior of the tube (corresponding with the cell-vacuole) contains a fluid called latex, consisting of an emulsion of fine granules and drops of very various substances suspended in a watery medium in which various other substances (salts, sugars, rubber-producers, tannins, alkaloids and various enzymes) are dissolved.
As a secondary function we may recognize, in certain cases, the power of closing wounds, which results from the rapid coagulation of exuded latex in contact with the air.
The trees are regularly tapped and the coagulated latex which exudes is collected and worked up into rubber.
Opium is obtained from the latex of the opium poppy (Pa paver somniferum), which contains the alkaloid morphine.
In some cases (Allium, Convolvulaceae, &c.) rows of cells with latex-like contents occur, but the walls separating the individual cells do not break down.
The rows of cells from which the laticiferous vessels are formed can be distinguished in many cases in the young embryo while still in the dry seed (Scott), but the latex vessels in process of formation are more easily seen when germination has begun.
RUBBER, INDIARUBBER or Caoutchouc (a word probably derived from Cahucha or Gaucho the names in Ecuador and Peru respectively for rubber or the tree producing it), the chief constituent of the coagulated milky juice or latex furnished by a number of different trees, shrubs and vines.
Latex, though chiefly secreted in vessels or small sacs which reside in the cortical tissue between the outer bark and the wood is also found in the leaves and sometimes in the roots or bulbs.
The latex exhibits a neutral, acid or alkaline reaction depending upon the plant from which it has been obtained.
This has been ascribed by some to the presence in " wild " rubber of certain impurities derived either from the latex or introduced during the preparation of the rubber which are thought to enhance the physical properties of the caoutchouc. It is more probable, however,.
Be feared that immature trees are often tapped and their latex mixed with that of older trees before coagulation, thus forming.
The latex of this tree flows less freely than that of Hevea brasiliensis, and the collection of large quantities of the latex is attended with considerable difficulty.
The latex is therefore usually allowed to coagulate on the tree, as it slowly exudes from the incision.
The latex, which is usually coagulated by standing or by heating, is obtained from incisions in the bark of the tree.
Besides the trees described above, a number of climbing plants or vines belonging to the Apocyanaceae secrete a latex which furnishes rubber of good quality.
The rubber is obtained by incising the stems of the vines and coagulating the latex by exposure, by admixture with acid vegetable juices or by heating.
Little is at present known of the large rubber tree of Tonkin (Bleckrodea tonkinensis), the latex of which is stated to furnish excellent rubber.
The latex is collected in the so-called dry season between June and February.
The trees are tapped in the early morning when the latex is most readily obtained.
To obtain the latex, deep incisions are made near the base of the tree extending up the trunk.
In three days, has a strong ammoniacal odour, which rapidly disappears, and in consequence of the loss of ammonia the latex will not keep for longer than a day unchanged; hence when it has to be carried to a distance from the place of collection, 3% of ammonia solution is added.
The latex usually furnished about 30% of rubber.
To obtain the rubber, the latex is usually treated in the following manner.
The seedlings rapidly developed and in most places in which they were planted grew into large trees which furnished satisfactory latex when tapped in their sixth or seventh year.
Africa the Hevea which has been planted promises well, especially in the Gold Coast, where good yields of latex are stated to have been obtained.
Latex-tubes abound in the tissues of Lactarius, Stereum, Mycena, Fistulina, filled with white or coloured milky fluids, and Istvanffvi has shown that similar tubes with fluid or oily contents are widely spread in other Hymenomycetes.
Several members of the order are used medicinally for the strong purging properties of the milky juice (latex) which they contain; scammony is the dried latex from the underground stem of Convolvulus Scarnmonia, a native of the Levant, while jalap is the product of the tubercles of Exogonium Purga, a native of Mexico.
RUBBERS Para Ceara Castilloa Ficus Landolphia Para Latex Rubber Rubber Rubber Elastica Kirkii (Ceylon).
At present the change of isoprene into caoutchouc is mainly of scientific interest in indicating possibilities with regard to the conversion of the liquid globules of the latex into rubber and to the formation of rubber by plants.
In the industrial working of indiarubber, the various impurities present in the crude " wild rubber (bark, dirt and the principal impurities derived from the latex, except resin) are removed by the following process: The lumps of crude caoutchouc are first softened by the prolonged action of hot water, and then cut into slices by means of a sharp knife - generally by hand, as thus any large stones or other foreign substances can be removed.
The latex is not to be confused with the sap of trees, on the circulation of which their nutrition depends.
The latex is usually obtained from the bark or stem by making an incision reaching almost to the wood when the milky fluid flows more or less readily from the laticiferous vessels.
If the latex is warmed or an acid, an alkali or astringent plant juice is added to it, " coagulation " usually takes place more or less readily, the caoutchouc separating in solid flakes or curds.
The efficacy of heat or of an acid, an alkali or other agent in promoting coagulation depends on the character of the latex, and varies with that obtained from different plants.
When exposed to air the latex gradually undergoes putrefactive changes accompanied by coagulation of the caoutchouc. The addition of a small quantity of ammonia or of formalin to some latices usually has the effect of preserving them for a considerable time.
There is, however, reason to believe that the coagulation of latex into rubber is not mainly of this character.