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Some gases when mixed will become solid, as muriatic acid gas with ammoniacal gas, producing a salt called sal ammoniac. Colours are altered, or deepened, or fixed to cloth by chemical attraction, which is the basis of dyeing; or discharged, as by chlorine or by charcoal; this is the basis of bleaching.
By the changes produced in the affinity of bodies from acting on each other, we learn to detect what peculiar matters are present. If we think iron is present in a solution, we add a little mixture of galls, and it will turn it all black; if copper, we add a little hartshorn, and a deep blue is produced. This is the basis of analysis; the galls and the hartshorn would be called tests; and the process, testing.
Chemical affinity is more strongly exerted between some substances than between others. Take sulphuric acid for instance: it will combine with 3 barytes in preference to potash; with potash in preference to soda; with this rather than magnesia; and with magnesia in preference to ammonia. This is called elective affinity.
From affinity results 'precipitation. For instance, in ink there is often a little blue-stone or sulphate of copper. Now iron has a greater affinity for sulphuric acid than the copper, and by consequence if you put a penknise into it, and draw away the acid, the copper must fall or be precipitated, which it does on to the knife. · Chemical attraction is modified, as by moisture for instance, which by dissolving bodies brings them into closer contact, and thus favours their attraction. Heat is also often necessary to effect this object, as in the joining of the fat and the alkali in making soap.
1. Vide Root. 2. Potash, called the vegetable alkali, is obtained from the ashes of vegetables. It is so named from being burnt in iron pots. Being again subjected to fire till it becomes white, it is called Pearl-ash. 3. Barytes, a very weighty earth found in lead inines, and there called heavy spar.
ASIA. In this quarter of the globe, the most wonderful events in the history of mankind have happened. Here Adam and Eve were created ; and on the banks of the Euphrates all the people dwelt who lived before the flood.
It was in Asia that the ark of Noah rested ; and here again the people began to build cities, and establish nations. Here the first great empire arose. Here the Jewish nation had its origin; and nearly all the events related in the Old Testament took place here.
It was in Asia that the religion which teaches us that there is one only living and true God had its origin ; and here Jesus Christ appeared to establish this religion, and seal the truth of revelation with his blood.
It was in Asia that Mahomet commenced and estáblished his false religion, which is now believed by so large a proportion of the human race. Several other false religions had their 'origin in Asia.
In Asia, some of the greatest empires have existed of which history gives us any account. The Assyrian empire is the first on record. This was followed by the Persian empire, which seemed to swallow up all the surrounding nations. China, the most populous empire on the globe, has endured longer than any other.
The Saracens, who extended their dominion over many countries, had their 'origin in Asia. The Turks, who have reigned over Palestine, Mesopotamia, Syria, Asia Minor, a part of Europe, and a part of Africa, for nearly eight hundred years, had their origin in Asia.
There is one portion of Asia which is, perhaps, more full of historical interest than any other on the face of the globe. It is that which lies between the Mediterranean
* 1. Vide Root.
on the west, Armenia on the north, Persia on the east, and Arabia on the south. Here is the spot on which the first inhabitants dwelt; here was the place where the first nations were formed; here the miracles recorded in the Bible took place; here the prophets appeared ; here Jesus Christ lived, preached, and died.
But although Asia was peopled before any other part of the world, and though the inhabitants have been favoured by miracles and the presence of a Divine Teacher, they are far behind the nations of Europe.
Jesus Christ is hardly known among the four hundred millions of people in Asia ; and though some of the rich men, kings, and princes live in gorgeous palaces, and are decked with gold and jewels, yet the mass of the people remain as they have done for ages, ignorant, poor, and degraded.
The most remarkable feature in the history of Asia is, that while the country has seen many revolutions and changes, the condition of the people remains nearly the sanie.
Mahometanism prevails over a great part of this portion of the globe ; and it is remarkable that no country, the people of which believed in this false religion, have ever been happy or well governed.
The Hindoos believe in Brahmanism, which teaches them that there is one principal deity, called Brahma, and several other inferior deities, called Vishnu, Siva, &c. They make strange images of these, and worship them. The priests are called Brahmins, and instruct the people in many idle ceremonies and cruel · superstitions.
GEOGRAPHICAL.- Area, 16,000,000 square miles. Population, 400 millions.
Light, Caloric, 8c. There are a four elements called 'imponderable, being of no perceptible weight, which exert great influence in the conformation of bodies :--they are light, heat, electricity, and magnetism. The nature of these is not fully ascertained.
Light in some cases produces what is terined chemical change, as may be seen in tarnished silver; whilst, in other cases, it bleaches, or changes the chemical state, so that a substance having a different colour results.
A pencil of light consists of coloured rays of red, orange, yellow, green, indigo, blue, and violet. It is at the violet end that chemical changes are chiefly produced. In some chemical changes, as in the decomposition or decay of fish and other animal matter, light is copiously evolved : phosphorus, a simple element, is always found to evolve light.
Caloric is that essence which gives warmth, and preserves fluids and gases from becoming solid. If we go near a fire, or concentrate with a lens the rays of the sun on the hand, the warmth produced is from caloric.
As at the violet end of a pencil of light a chemical ray exists; so at the other end or red ray, there is a ray of heat or caloric.
Caloric is said to be sensible in the instances now noted; but there is another state in which it is not sensible, that is, but for reasoning we should know nothing of it; here it is said to be latent. Pour, for instance, a little boiling water on some ice, but not enough to melt it all: the water about the remaining ice will not be hotter than the ice itself, the caloric or heat of the boiling water is all gone, that is, it is no longer sensible. So, before water can be frozen, a great quantity of latent heat is given out; and before ice can be melted, much heat, before sensible, is 'absorbed. The caloric here lost has been absorbed by that portion of the ice that is melted, and is now occupied in keeping it Auid. It is latent heat that is made sensible when iron is beaten until red hot, or pieces of dry wood rubbed until inflamed.
This leads to another point, that it is by latent heat that we have fluids, and gases or vapours. Take caloric away, all would be solid. Take caloric away from mercury, and it becomes solid like silver; near the north pole, where some of our navigators have gone, there is so little caloric that this has happened in the open air. Add caloric to ice, and it becomes water, - this is called liquefaction ; add more, and it becomes steam,—this is called vaporization ; add caloric to iron, it becomes fluid, --this also is liquefaction; and if you could heat it 8 high enough, it probably would become vapour.
When you add water to * quick-lime, so much heat is suddenly levolved as to inflame phosphorus, or burn the hand. The reason of this is, that the latent heat of the water is evolved or made sensible because the water joins the lime, and becomes solid ; and as solid, it has much less latent heat.
It appears that all bodies possess latent heat, but in different proportions : thus spirit of wine has its latent heat, and water its latent heat; mix them together, and the compound is much warmer than they were when separate ;-how is this ?-because the compound does not in its nature want so much latent heat as either separately, and so it becomes sensible, and is given off.
1. Vide Root. 2. The ancients believed all things to be composed of what they called the four elements-fire, air, earth, and water, which chemistry has shown not to be simple elements. 3. T'he heat of melted iron is too intense to be measured by the thermometer; it is ascertained by an instrument made of clay, called a pyrometer, or fire measurer. 4. Quick or living. Lime is said also to be küled when water is thrown on it.