Part 12 (1/2)
Consult a good physiology and learn the effects of coffee, tea, tobacco, and opium.
Where and what are the following: Mocha, Java, Maracaibo, Yokohama, Amoy, Canton, Oaxaca, Hodeida, Rio Janeiro, Santos, Havana; how is each connected commercially with this chapter?
From the map, Fig. 1, trace the route of a cargo of tea overland from China to Great Britain.
Consult an English history or a cyclopaedia and learn about the opium war.
FOR STUDY AND REFERENCE
Obtain samples of the following, preserving them for study and inspection in closely stoppered vials: Mocha, Java, Rio, and Sumatra coffees; green, black, and gunpowder tea. Soak a tea-leaf a few minutes in warm water; unroll the leaf and attach it to a white card, for study.
Obtain samples of gum opium, laudanum, and morphine; note the odor of the first two and the taste of the last. Remember that they are poisonous.
Unroll a cheap cigarette and note the character of the tobacco in it, using a magnifying gla.s.s.
CHAPTER XI
GUMS AND RESINS USED IN THE ARTS
Most vegetable juices exposed to the air harden into firm substances, commonly called _gum_. Some of these dissolve, or at least soften, in water; these technically are known as ”gums,” and usually are so designated in commerce. Others are insoluble in water, but dissolve readily in alcohol, in naphtha, in turpentine, or in other essential oils; these are designated as ”gum-resins.” Still others yield oils or pitchy substances on distillation; these are known as ”oleo-resins.”
There are many other dried vegetable juices, however, that in commerce are not cla.s.sified among the gums and resins, and of these the most important is the substance commonly known as india-rubber.
=Rubber and Rubber Products.=--”Caoutchouc” is approximately the name given by Indians of the Amazon forests to a substance that had also been found in India. Some of it was brought to Europe from the Amazon region as early as 1736, and for nearly one hundred years no general purpose was discovered for which it could be used, except to erase lead-pencil marks--hence the name india-rubber, which has held ever since.
Common rubber is the prepared juice of a dozen or more shrubs and trees, all of which grow in tropical regions.[37] The belt of rubber-producing plants extends around the world and includes such well-known species as the fig, the manihot (or manioc), and the oleander; indeed, it is a condition of sap rather than a definite species of plant that produces rubber, and the latter is a manufactured rather than a natural product.
The process of preparing the juice is practically the same in every part of the world.
The rubber-gatherer of the Amazon, who is practically a slave, wades into the swamp, makes several incisions in the bark of the tree, fas.h.i.+ons a rough trough of clay under it, and waits till the sap fills the clay vessel. When the sap has been gathered he makes a fire of the nuts of the urucuri palm and places an inverted funnel over it to concentrate the smoke. He first dips the end of a wooden spindle into the juice and then holds it in the smoke until the juice coagulates; this process is repeated until there has formed a ball of rubber weighing from five to ten pounds. The smoke of the palm-nuts is a chemical agent that converts the juice into the crude rubber of commerce.
Crude gum, however, is lacking both in strength and elasticity. The process that makes it a finished product is known as _vulcanization_.
The crude rubber, having been exported to the manufacturer in the United States or Europe, is shredded, washed, and cleansed, and partly fused with varying proportions of sulphur. For a very soft product, such as the inner surface of tires, only a small proportion is used; where the wear is considerable, a larger proportion is employed.[38] White clay is sometimes added to give body to the product; coloring matter is also sometimes added.
By far the greater part of the crude rubber comes from the Amazon forests. Brazil produces about one-half, but a considerable quant.i.ty is obtained in Acre, the territory formed where the borders of Brazil, Bolivia, and Peru meet, and now ceded to Brazil. Nearly all this product, that of the Ceara region excepted, is marketed at Para and is known as Para rubber. It is the best produced. The African product, mainly from the forests of the Kongo, and Madagascar, and nearly all the East Indian product is sent to Europe.
[Ill.u.s.tration: REGIONS YIELDING RUBBER]
The world's product is about one hundred and thirty-three million pounds of crude rubber. Of this product the United States takes nearly one-half. The greater part is used in the manufacture of pneumatic tires, hose, and overshoes. A large part is used for making water-proof cloth,[39] and considerable is made into the small elastic bands for which there is a growing use.
=Gutta-Percha.=--Gutta-percha is obtained from the juices of several plants (chiefly _Dichopsis gutta_ and _Supota mulleri_) both of which abound in the Malay peninsula and the East Indies. It is prepared in a manner somewhat similar to that employed in making crude rubber; it is also easily vulcanized by heating with sulphur. It is used to a limited extent in the manufacture of golf-b.a.l.l.s, but mainly as the insulating cover of copper wires used in ocean telegraph cables. For this purpose it has no known subst.i.tute, and its essential merit is the fact that it is not altered by salt water. Nearly all the product is s.h.i.+pped from Singapore to England.
=Pine-Tree Products.=--The various members of the pine and cone-bearing trees yield valuable essential oils and oleo-resins that are very important in the arts and sciences. These, in nearly every instance, are prepared from the sap of the tree.
_Oil of turpentine_ is known as an ”essential oil,” and in chemical structure and properties it does not differ from the various essential oils, such as lemon, orange, peppermint, etc. Commercial turpentine is generally made from the sap of the long-leafed pine of the Atlantic coast-plain.