Part 10 (2/2)

Malleable iron, exposed to a red heat in contact with charcoal, called _cementation_, converts it into _steel_, which has the properties of beco firstit in cold water By first rees of heat, and cooling it in those different degrees, it is capable of a great variety of _terees of heat worke of colour on its surface Steel, like crude iron, is capable of beingits properties It is then called _cast steel_, and is of a ht by being converted into steel; and when dissolved in acid, it yields ravity than iron If the ce, the steel acquires a darkish fracture, it isSteel heated in contact with earthy matters, is reduced to iron

Iron is the only substance capable of _ netism The loadstone is an ore of iron

LECTURE XXVI

_Of Tin_

Tin is a h harder than lead, very reat tenacity; so that wires cannot be made of it It easily extends under the hammer, and plates of it, called _tinfoil_, are ht be ravity than any other nition, at 410 of Fahrenheit, and by the continuance of heat is slowly converted into a white powder, which is the chief ingredient in _putty_, used in polishi+ng, &c Like lead, it is brittle when heated little short of fusion, and itation as it passes from a fluid to a solid state

The calx of tin resists fusion more than that of any otheran opaque white enaht surface when exposed to the air, but is not properly subject to rust; so that it is useful in protecting iron and other metals from the effects of the atmosphere

Concentrated vitriolic acid, assisted by heat, dissolves half its weight of tin, and yields vitriolic acid air Withthe solution the phlogiston of the tin uniting with the acid, for, or the addition of water, the calx of tin is precipitated from the solution The nitrous acid dissolves tin very rapidly without heat, and yields but little nitrous air With ia it assuhten the colour of so wool

A transparent liquor, which emits very copious fu liquor of Libavius_, is aether A colourless liquor comes over first, and then a thick white fume, which condenses into the transparent liquor above mentioned Mr

Adet has shewn, that this liquor bears the same relation to the common solution of tin, that corrosive sublienious solution of many of its properties

Tin detonates with nitre; and if the crystals made by the solution of copper in the nitrous acid be inclosed in tinfoil, nitrous fumes will be emitted, and the whole will becoht of sulphur be added to melted tin, a black brittle compound, which readily takes fire, will be formed

Another coht yellow substance called _aururedient in the co lead, zinc, bis his peculiar receipt It is also used in coating copper and iron plates, and in silvering looking-glasses, besides being cast into a variety of forms, when it is called _block tin_

Tin is soenerally ht to be always contained in tin, and to be the cause of the crackling noiseplates of it

_Of the Semi-metals_

Bismuth is a semi-metal of a yellowish or reddish cast, but little subject to change in the air; harder than lead, but easily broken, and reducible to powder When broken it exhibits large shi+ning facets, in a variety of positions Thin pieces of it are considerably sonorous

Bisnites, and burns with a slight blue flame, while a yellowish calx, called _flowers of bislass In a strong heat, and in close vessels, this metal subli, has but little effect upon bisreatest rapidity and violence, producing isticated nitrous vapour From the solution of bisistery of bismuth_, is precipitated by the affusion of water This has been used as a paint for the skin but has been thought to injure it

The marine acid does not readily act upon bismuth; but when concentrated, it forms with it a saline combination, which does not easily crystallize, but may be sublimed in the form of a soft fusible salt, called _butter of bismuth_

Biseneral renders them more fusible When calcined with the imperfect metals, it unites with them, and has the same effect as lead in cupellation

Bismuth is used in the composition of pewter, in printers' types, and other metallic mixtures

This metal is sometimes found native, but more commonly mineralized with sulphur