TIME civil, is the former time accom modated to civil uses, and 6.rraed and distinguished into years, mouths, days, &c. , 'nun, in music, is an affection of sound, whereby we denominate it long or short, with regard to' its continuance in the same degree of time.
TIN, in mineralogy, a genus of metals, of which there are three species: Tin-pyrites; colour intermediate between steel-grey and brass.yellow ; .but usually more inclined to the first; it occurs Mis sive and disseminated; internally it is glistening, sometimes shining, and seldom passing into splendent ; its lustre is ; it is brittle, and the specific gra: city is somewhere between 4.3 and 4.8. Before the blow-pipe, it gives out a sul phureous odour, and melts easily, with out being reduced, into a black scoria. IC communicates a yellow or green colour to borax. It consists of Tin 34 Copper '36 Iron 3 Sulphur 25 Earth 2 100 It is found at Wheal-rock and St. Ag nes in Cornwall, where it occurs in a vein about nine feet wide, accompanied with copper pyrites and brown blende.
2. Tin-stone, which is hard, brittle, and very heavy, the specific gravity being from 5.8 to 6.9 or 7• Before the blow pipe it decrepitates, becomes paler, and, where it rests on the charcoal, is reduced. NVhen roasted, it is converted into a grey oxide. A specimen, analysed by Klap. roth, contained Tin 77 50 Iron 0 25 Oxygen . . , . 21 50 Silica 75 100 00 It occurs only in primitive rocks, granite, gneiss; mica-slate, and clay-slate, and is said to be the oldest of all the me. tats. It occurs either disseminated in the rock, or in, beds, or veins. It is usually accompanied with quartz, mica, &c. and is als:: found in great quantities in alluvial land. The greater part of the English, much of the Spanish; and the greater proportion of that from India, occurs in that situation.
Tin is not fcrund in many. countries ; but where it exists at all, - it is in very considerable quantities. In Europe there are only three tin districts : the first is in Saxony and Bohemia ; the second in Cornwall ; and the third is that of Galli cia, on the borders of Portugal. It is found in many parts of Asia, and in South America. It is worked as an ore of tin, and from it all the tin of commerce is ob tained. Its name is derived from the quantity of tin which it affords, and its unmetallic aspect.
3. Cornish tin-ore, or wood tin ; which, like the last, is very heavy ; before the blow-pipe it is infusible ; it consists of about 63 parts of tin, with iron and arsenic. , It has hitherto been found only in Cornwall, and there in alluvial land. It is very like brown hematite, from which it is distinguished by its colour, its rolled pieces, greater hardness, and higher spe cific gravity. We now turn to tin, in a chemical view.
Tin is a metal of a silver-white colour, very ductile, and malleable, gives out, while bending, a crackling noise, is fusi ble at a heat much less than that of igni tion, is soluble in muriatic acid, and, by dilute nitric acid, is rapidly converted in to a white oxide. Tin has been known from the earliest ages. It was much em ployed by the Egyptians in the arts, and by the Greeks as an alloy with other me tals. Pliny speaks of it under the name of white lead, as a metal well known in the arts, and even applied in the fabrica tion of many ornaments of luxury. He ascribes to the Gauls the invention of the art of tinning, or covering other metals with a thin coat of tin. The alchemists
were much employed in their researches concerning tin, and gave it the name of Jupiter, from which the salts, or prepara tions of tin, were called jovial. Since their time, the nature and properties of tin have been, particularly investigated by many chemists, and it has proved the subject of some important discoveries in chemical science. Tin exists in nature in three different states. 1. It is found native ; 2. In the state of oxide ; and, 3. In that of sul pl rurated oxide. Native tin is in brilliant plates, or regularly crystal lized. The native oxide of tin, which is the most common ore of this metal, ex ists under a variety of forms. It is gene rally found crystallized. The sulphuret of tin is of a pale, or dark:grey colour, and, when pure, has some resemblance to an ore of silver. To obtain the metal from its ores, they are first roasted, and then treated with a flux, to reduce the metal. After the ore is roasted, it fuses readily with three times its weight of black flux, and a little decrepitated mu riate of soda. In the humid way, native tin may be dissolved in nitric acid, which readily oxidates, and reduces it to the state of white powder, which is an oxide of tin ; and if it contain iron and copper, these two metals remain in the solution. Tin is of a white colour, nearly as bril liant as silver. The specific gravity of tin is nearly 7.3. It is one of the softest of the metals. It is extremely flexible, and so malleable, that it can be easily beaten out in plates to ran. part of an inch, which is the thickness of tinfoil. It has little elasticity or tenacity. A wire of this metal, about one-tenth of an inch in diameter, supports a weight of about thirty pounds, without breaking. Tin is susceptible of very considerable expan sion, by means of caloric, and on this ac, count it has been proposed to employ it as a pyrometer. Tin is one of the most fusible of the metals, and melts at the temperature of 442°; but it requires a very high temperature- to raise it in va pour. If it be 'allowed to cool slowly, and when the surface becomes solid by pouring out part of the liquid metal, crystals are formed, composed of a great number of small needles. Tin is a good conductor of electricity. It possesses a peculiar odour, which is communicated to the hands by friction. It has also a per ceptible taste. When this metal is ex; posed to the air, it is soon tarnished, and assumes a greyish white colour ; but it undergoes no further change. When it is melted in an open vessel, it is soon co vered with a greyish pellicle, which is the commencement of the oxidation of the metal. When this pellicle is remov ed, another forms, and so on successively, till the whole is oxidated. By continuing the heat, and by agitation, the process goes on more rapidly, and the metal is converted into a whitish powder. This oxide contains about twenty parts of oxy gen in 100 of the metal. With the addi tion of lead, to promote the oxidation, this oxide is the putty of tin. It contains about two parts of oxide of lead, and one part of oxide of tin. But when tin is strongly heated, it is converted into a fine white oxide, which, during the protegs, gives out a vivid white flame. This ox ide is condensed in the cold, and crystal lizes in shining, transparent needles.