Lecture Xxvii.

Of Nickel.

Nickel is a semi-metal of a reddish cast, of great hardness, and always magnetical; on which account it is supposed to contain iron, though chemists have not yet been able to separate them.

The purest nickel was so infusible as not to run into a mass in the strongest heat of a smith's forge; but then it was in some degree malleable.

Concentrated acid of vitriol only corrodes nickel. Alkalies precipitate it from its solution in the nitrous acid, and dissolve the precipitate. It readily unites with sulphur.

Nickel is found either native or mineralized with several other metals, especially with copper, when it is called kupfer nickel, or false copper, being of a reddish or copper colour.

This semi-metal has not yet been applied to any use.

Of Arsenic.

What is commonly called arsenic is the calx of a semi-metal called the regulus of arsenic. It is a white and brittle substance, expelled from the ores of several metals by heat. It is then refined by a second sublimation, and melted into the masses in which it is commonly sold. This calx is soluble in about eighty times its weight of cold water, or in fifteen times its weight of boiling water. It acts in many respects like an acid, as it decomposes nitre by distillation, when the nitrous acid flies off, and the arsenical salt of Macquer remains behind.

When the calx of arsenic is distilled with sulphur, the vitriolic acid flies off, and a substance of a yellow colour, called orpiment, is produced. This appears to consist of sulphur and the regulus of arsenic; part of the sulphur receiving pure air from the calx, to which it communicates phlogiston; and thus the sulphur becomes converted into vitriolic acid, while the arsenical calx is reduced, and combines with the rest of the sulphur.

The combination of sulphur and arsenic, by melting them together, is of a red colour, known by the name of realgal, or realgar. It is less volatile than orpiment.

The solution of fixed alkali dissolves the calx of arsenic, and by means of heat a brown tenacious mass is produced, and having also a disagreeable smell, it is called liver of arsenic.

The regulus of arsenic is of a yellow colour, subject to tarnish or grow black, by exposure to the air, very brittle, and of a laminated texture. In close vessels it wholly sublimes, but burns with a small flame in pure air.

Vitriolic acid has little action upon this semi-metal, except when hot; but the nitrous acid acts readily upon it, and likewise dissolves the calx, as does boiling marine acid, though it affects it very little when cold.

Most of the metals unite with the regulus of arsenic.

Dephlogisticated marine acid converts the calx of arsenic into arsenical acid by giving it pure air.

The acid of arsenic acts more or less upon all metals, but the phenomena do not appear to be of much importance.

The calx of acid is used in a variety of the arts, especially in the manufactory of glass. Orpiment and realgar are used as pigments. Some attempts have been made to introduce it into medicine, but being dangerous, the experiments should be made with caution.

Of Cobalt.

Cobalt is a semi-metal of a grey or steel colour, of a close-grained fracture, more difficult of fusion than copper, not easily calcined. It soon tarnishes in the air, but water has no effect upon it.

Cobalt, dissolved in aqua regia, makes an excellent sympathetic ink, appearing green when held to the fire, and disappearing when cold, unless it has been heated too much, when it burns the paper.

The calx of cobalt is of a deep blue colour, which, when fused, makes the blue glass called smalt. The ore of cobalt, called zaffre, is found in several parts of Europe, but chiefly in Saxony. As it is commonly sold, it contains twice or thrice its weight of powder of flints. The smalt is usually composed of one part of calcined cobalt, fused with two parts of powder of flint and one of pot-ash.

The chief use of cobalt is for making smalt; but the powder and the blue-stone used by laundresses is a preparation made by the Dutch of a coarse kind of smalt.

Of Zinc.

Zinc is a semi-metal of a bluish cast, brighter than lead, and so far malleable as not to be broken by a hammer, though it cannot be much extended. When broken by bending, it appears to consist of cubical grains. If it be heated nearly to melting, it will be sufficiently brittle to be pulverized. It melts long before ignition, and when it is red hot, it burns with a dazzling white flame, and is calcined with such rapidity, that its calx flies up in the form of white flowers, called flowers of zinc, or philosophical wool. In a stronger heat they become a clear yellow glass. Heated in close vessels, this metal rises without decomposition, being the most volatile of all the metals except the regulus of arsenic.

Zinc dissolved in diluted vitriolic acid, yields much inflammable air, and has a residuum, which appears to be plumbago, and the liquor forms crystals, called white copperas. This metals also yields inflammable air when dissolved in the marine acid. Dissolved in the nitrous acid, it yields dephlogisticated nitrous air, with very little proper nitrous air.

The ore of zinc, called calamine, is generally of a white colour; and the chief use of it is to unite it with copper, with which it makes brass and other gold-coloured mixtures of metals. The calx and the salts of this metal are occasionally used in medicine.