Sulphur is a simple inflammable mineral abounding in volcanic countries, either in a crystalline or amorphous state, and forming a constituent in organic substances, animal and vegetable. It is readily dissolved by bisulphide of carbon, by benzine, and by a moderate heat; and copper filings exposed to its vapour spontaneously take fire, the chemical force of combination merging into light and heat. Sulphuretted hydrogen gas, a combination of sulphur and hydrogen, forms naturally during the putrefaction of organic matter, and Mr. Faraday observes with regard to the affinities of sulphur, ‘so numerous are its relations, so extensive its range of combinations, that we must consider it to be the very foundation on which chemical manufacture is built up.’
Though a simple substance, sulphur exhibits the two remarkable phenomena of dimorphism and the allotropic property. When reduced by heat to vapour and cooled slowly, it crystallizes in rhombic octohedrons; when merely melted and allowed to cool slowly, it takes the form of oblique rhombic prisms. Here the same atoms when in vapour and in a liquid state are acted upon by different forces; but however that may be, sulphur is another singular exception to the law of the immutability of the crystalline systems.
Sulphur becomes allotropic by the continued application of heat; that is to say, it entirely changes its appearance and character, though it remains chemically the same. Naturally it is yellow and brittle, but when fused, it is a colourless pellucid fluid which by continued heat is changed into a black tenacious substance that becomes like India rubber or gutta percha when thrown into water. In this allotropic state it is endowed with properties more powerful, energetic, and exalted; its tendencies to act chemically being increased like those of ozone. That this black tenacious substance is chemically the same with common sulphur there can be no doubt, for when it is exposed to greater heat, it again becomes a colourless pellucid fluid, which thrown into water resumes the form of brittle yellow sulphur.
These new arrangements among atoms of the same kind show that the immutability of matter is not without exceptions.
The animal kingdom is the great reservoir of phosphorus, a simple substance that is never found uncombined. It is sparingly met with in the vegetable kingdom, and still less in the mineral, but may be procured abundantly from calcined bones. When pure it is colourless, transparent, solid, extremely poisonous, and so inflammable that it must be kept in water. In air it is in continual combustion with oxygen, during which ozone is produced. When burnt in a current of air phosphorus leaves a residuum consisting of two substances, of which one is an acid, the other is red allotropic phosphorus, which has been extensively used in the manufacture of lucifer matches, because its fumes are not deleterious, and because it inflames less easily than common phosphorus, to which it is reduced by heat or friction, which generates heat.
Silicon is a simple substance, never found alone, but when forty-eight parts of it are combined with fifty-two parts of oxygen gas it forms rock crystal, the purest form of silica or quartz. Silica is so abundant that it may be said to constitute the basis of the mineral world. The sand on the sea-shore, which is the debris of quartz rocks, shows how universally it prevails. It is even abundant in the vegetable kingdom, giving strength to the stalks and leaves of the grasses, and may be felt in the harshness of the beards of wheat and barley. Silicon exists in three different states—the amorphous, which has no form; the graphic, which takes the form of small hexagonal plates; and that of octohedral silicon: hence this substance is dimorphous.
A singular analogy obtains between silicon and carbon: the amorphous form of silicon corresponds to charcoal, the graphic form of silicon corresponds to the graphic form of carbon, and the octohedral form of silicon to the diamond; yet the chemical relations between the two substances are very small.
Silica has hitherto been considered to be insoluble in pure water; at least M. Bischoff states that only one part of silica dissolves in 769,230 parts of water; but by a method hereafter to be explained, Professor Graham has actually obtained a limpid solution of silica in pure water.
Boron is a constituent of boracic acid, a natural production in Thibet and Monte Corbalo in Tuscany. It is a greenish-brown solid, insoluble in water, but when heated to about 600° it burns in open air with a vivid flame.
Fluorine is a constituent of a very beautiful mineral, well known as fluor spar, which is found in cubic crystals of a green, yellow, or purple colour. Hydrofluoric acid obtained chemically from the mineral is highly volatile and extremely corrosive.