It has

Sp. gr.

Its pro

native, in great quantities.-21. CHROMIUM. Its colour is white; sp. gr. 5,90. It is very brittle, is of a good polish, and magnetic. It melts only in a very high temperature: on being heated in the open air, it becomes oxidized. The protoxide is green, the deutoxide is brown; and the peroxide or chromic acid is of a red or rather orange colour, and is found in redlead ore, and contains one part chromium and two of oxygen.-22. Tellurium is found in Saxony, in an ore named peckblende. It is of an iron grey colour; sp. gr. 9,000. It yields to the file; but can only be fused by the highest degrees of heat. It is said to form four oxides.-23. MOLYBDENUM. been obtained only in a granular form. 8,611. It is brittle, and of a silvery white. toxide is brown; the deutoxide is of a violet brown. By increasing the heat it is farther oxidized, and becomes blue, manifesting several acid properties. It then consists of 100 parts metal, and 34 oxygen, and is called molybdous acid. On being farther oxidized it becomes white, and is termed the molyb dic acid.-24. TUNGSTEN is of a greyish white, and brilliant. Sp. gr. 17,6. It is brittle, very hard and very difficult of fusion. It forms two oxides; the protoxide or blue, and the peroxide or yellow oxide.-25. TITANIUM. It is extremely refractory; is brittle, but yet somewhat elastic. It has some lustre, and is of the colour of copper. The protoxide is blue or purple; the deutoxide, composed of 100 metal and 33 oxygen, is red; and the

peroxide, with two parts metal and one of oxygen, is white. 26. COLUMBIUM was discovered by Mr. Hatchett, in a mineral from America. He procured from it a metallic oxide, but could not obtain it in a metallic form. It is supposed to be the same substance which Ekeberg, a Swedish chemist, discovered, and to which he gave the name of TANTALIUM.-27. CERIUM was discovered by Hisinger and Berzelius. They were only able to ob→ tain it in the state of oxide, being foiled in every attempt to reduce it to a metallic state.

The Wegetable Kingdom.

Whether we regard the numerous processes performing in the systems of different vegetables, or consider the various essentially different products which result from them, the vegetable kingdom offers us manifold beautiful instances of the chemistry of nature.

Water may be esteemed the chief pabulum of vegetables, which reducing it to its first principles, appropriate its hydrogen and oxygen to the formation of their respective constituent parts. Air, light, and heat, aid the several processes, whilst the application of manure not only adds to the quantity of nutriment, but at the same time stimulates the vegetating principle to increased action. The SAP appears to be, in vegetables, what the blood is in animals: from this the other humours are secreted. It differs somewhat in different vegetables, but always contains water, mucus, sugar, gum, extractive matter, tannin,

&c.: principles from which nature separates several useful and surprising productions. Thus, MUCUs is secreted in large quantities in the leaves of mallows, in quince and lint-seed, and in different bulbs, as of the hyacinth, white lily, &c. This mucus, which had hitherto been thought to be similar to gum, has been ascertained by Dr. Bostock to be really different from it. GUM exudes from different trees, varying in its properties, with the trees from which it exudes; such are the gum arabic and tragacanth. ALBUMEN, a substance resembling white of egg, has also been found in many vegetables, particularly in the papan-tree, or carica papaya. Even FIBRIN, well known to exist in the blood and flesh of animals, is found in the same tree which yields albumen. Wheat-flour, too, yields a substance named GLUTEN, which very much resembles the animal membrane or tendon, and, when dry, has much the appearance of glue. It is obtained by kneading wheat-flour in water: this substance remaining in the hand, whilst the water will be found to contain STARCH, which has also been yielded by the flour: starch is also found in many seeds and bulbous roots. SUGAR abounds in many vegetable substances, particularly in grapes, parsnips, and beet-root. It is most plentifully yielded by the sugar-cane, arundo saccharifera. It is first obtained in a fluid state, and by long boiling is deposited in crystals, when it is said that it grains. The molasses or fluid-sugar being drained from these grains, they are termed raw-sugar; and

this being properly purified and clarified, becomes loaf-sugar. MANNA may be considered as a species of sugar. It is obtained from various trees, from which it exudes spontaneously in the summer months: sometimes the exudation being promoted by incisions made into the tree. It is chiefly obtained from Sicily and Calabria, from the fraxinus ornus, a species of ash. Jelly, a soft tremulous substance, is yielded by the juices of currants and of several other fruits. It would be well to remember, that, when long boiled, these juices lose their power of forming into a jelly. The ulmus nigra, a species of elm, exudes a substance, which the celebrated Klaproth first examined. It appears like gum, but is of a black colour, with considerable lustre. It is solid and hard; its powder is of a brown colour, and it dissolves readily in the mouth, and is tasteless. The inula helenium, or elecampane, yields also a peculiar substance, which appears like starch: being rubbed in cold water, it gives to it an opaline appearance, but if suffered to rest, falls in the form of a white powder. It is also precipitated in the same manner, after having been actually dissolved in boiling water. To this substance has been given the name of INULIN. That most valuable colouring substance, INDIGO, of so much use in the art of dyeing, is obtained from different species of plants termed indigofera, and mostly from that species which is named tinctoria. These plants are steeped in water until fermentation takes place, by which

the water assumes a green colour. The water now being agitated for some time, lime water is added to it, when blue flocculi, which is the indigo, subside, and the collected masses are dried for use. In many vegetables, a remarkably strong bitter taste is discoverable, as in the hop, quassia, and gentian. This is supposed to proceed from the presence, in these plants, of a peculiar vegetable substance, which has been named the BITTER PRINCIPLE, although it has not yet been obtained pure and distinct in a separate state. A substance has been formed by the action of the nitric acid in different vegetable substances, which, from the peculiar properties it possesses, has obtained the name of the ARTIFICIAL BITTER PRINCIPLE. TANNIN, of so much use in the preparation of leather and in dyeing, is obtained from nutgalls, the barks of different trees, and from several other vegetable substances, by infusion and subsequent deposition. It is of a brown colour and an astringent taste, and is soluble in water. If this solution be mixed with a solution of gelatine or glue, the two substances unite, and a precipitate of tannin and gelatine falls. It is on this combination that the process of tanning depends. Tannin combines with most of the metallic oxides, and strikes therewith different colours. Hence its use in dyeing, ink-making, &c. Added to solutions of iron, it forms a purple or deep black. Mr. Hatchett has ascertained that charcoal, of either vegetable or animal substances, if digested with nitric acid, will yield a substance, which, as it is capa