similar form, are liquids. Its atomic weight is 69, (451 chlorine + 24 olefiant gas).

Chlorides of Carbon.—Perchloride of Carbon, (Faraday).— By causing chlorine in unlimited quantity to act upon chloric ether in the sunbeam, Mr Faraday derived from it another substance, which condensed in dendritic crystalline spicula on the sides of the vessel. It consists of alternate particles of chlorine and carbon, and is, therefore, analogous to phosphorana. It has been named Perchloride of Carbon; but if the views here advanced be adopted, the discoverers of many chemical substances will not refuse to give them more expressive names.

When the chlorine is supplied in abundance, it thus distributes the olefiant gas very economically, the olefiant particles in every particle of chloric ether being able to engage five of chlorine, besides its own nucleus, two as muriatic acid and three as the perchloride of carbon, in which state the nucleus itself is left. This substance is a friable white solid, having the appearance of sugar when scratched. It has little taste, but its odour is like that of camphor. It is not readily combustible, nor easily destroyed by the action of the stronger acids. It is volatile, subliming like camphor towards the light. It may be fused, and made to boil. It is sparingly soluble in water, but readily in alcohol and ether, and its alcoholic solution, like that of camphor, is decomposed by water. Its atomic weight is 50, (451 chlorine + 51 carbon).

Protochloride of Carbon, (Faraday).—By subliming the former substance in a state of minute division, Mr Faraday succeeded in parting it into two, one of which was pure chlorine, and the other chlorine charged with a particle of carbon on each pole; it is therefore analogous to sulphurane and phosphurane, and, like these bodies, is a liquid. It retains an odour of camphor, and, like the other, has a very high refractive power. It unites readily with alcohol, ether, volatile and fixed oils,

but not with water. Held in the flame of a spirit-lamp it burns with a bright yellow flame, giving off fumes of muriatic acid.

The Chloride of Carbon from Abo.-During the process of preparing nitric acid from crude nitre at Abo in Finland, very small quantities are formed of a substance found in soft adhesive fibres, of a white colour, and an odour somewhat resembling spermaceti. On the application of heat it fuses and boils. At a lower temperature it sublimes, condensing in the form of long needles. Chemists have not yet succeeded in forming it otherwise, but its analysis shews that it consists of a ternate molecule of carbon (Fig. 63) united to a particle of chlorine. Its atomic weight is therefore 60, (45i chlorine + 153 carbon). In these interesting substances the relation of the base of chlorine to the organic kingdom, is shewn in a very satisfactory manner.

Chloro-carbonic Acid.-By exposure to the sunbeam in equal volumes, chlorine and carbonic oxide unite. They contract to half their volume, and an acid gas is the product. Its structure is analogous to muriatic and phosphorana acid. Its atomic weight is 65, (451 chlorine, 201 carbonic oxide). Its elements are held united by a weak affinity.

MANGANESE.

CARBON, when existing in the mineral strata uncombined with oxygen as carbonic acid, constitutes great beds of plumbago and anthracite. But it is also very abundantly distributed in the mineral kingdom in septenate molecules, which may possess either of two arrangements. The poles of this form (Fig. 65) are, however, eminently conformable to oxygen; hence, in nature, the septenate molecule always occurs in union with oxygen. The oxygen with which the molecule is

united, can be wholly expelled only with extreme difficulty, as by a continued application of the most intense heat that can be raised, and the presence of charcoal to carry it off as carbonic acid. In this way, and even by the application of fire without charcoal, the carbonaceous molecule has been obtained in a pure state. It is known by the name of Manganese. Its lustre is probably somewhat higher than that of coke. Both are equally metallic. Like charcoal it is extremely infusible, and has only been procured in a few small globules. The weight of manganese is about double that of the diamond, and both are brittle.

In this body there is an equatorial and polar region very perfectly developed; hence it is not in an inactive and quiescent state, like the duodenate molecule. It draws down the

oxygen from the air, loses its lustre, and becomes an earthy friable body. Its affinity for oxygen is so great that it decomposes water with rapidity; the hydrogen disengaged carrying up some of the manganese, and acquiring the odour of assafoetida, which is a hydro-carbonaceous production of vegetation.

Peroxide, Black Oxide of Manganese.-The number of forms which may result from the union of manganese with oxygen may be very great. That which possesses the ratio most near saturation, at a natural temperature, appears to be when a particle of manganese has one of oxygen on each pole, (Fig. 78). The atomic weight of manganese being 35 (357 carbon), that of this, the most natural form in which it occurs, is 55 (35i manganese + 202 oxygen); and it is 202 met with in nature very abundantly. It is usually associated with silex, alumina, iron, lime, and magnesia; but it appears, from the analysis of Professor Turner, that the Pyrosulite from Elgersburg consists of this oxide almost in a state of purity. As it usually occurs, it is not a crystalline but an earthy mineral, having a very carbonaceous aspect, and some varieties, like plumbago, have a greasy touch, and a dark streak. This oxide, which is commonly known by the

name of Manganese, is very useful both in the laboratory of the chemist, and in the arts. It is found in such abundance all over the central parts of Europe and in England, that it is employed in the manufacture of glass, and in bleaching. When mingled in certain quantities with impure glass in a state of fusion, discoloured by combustible matter, it yields oxygen to the combustible, and the mass becomes limpid. If, again, it be mixed in a larger proportion, the whole acquires an amethystine tint, which seems to be that proper to this oxide. To its presence in fact the amethyst owes its colour.

Manganese is also used for disengaging chlorine from seasalt, of which it constitutes more than a half. For this purpose diluted oil of vitriol is poured upon a mixture of salt and manganese, and heat applied. The vitriol demands the soda of the salt, and forms with it Glauber's salt. The muriatic acid set free might unite with the protoxide of manganese, and pure oxygen gas be evolved, were it not that the vitriol demands the protoxide also. Hence for every two particles of vitriol that are engaged (one with soda and another with protoxide of manganese), one of muriatic acid and one of oxygen are set free. The oxygen unites with the hydrogen of the muriatic acid, water is generated, and the chlorine escapes in the gaseous form.

Green Oxide. If vitriol only be poured upon the man. ganese, and heat applied, pretty pure oxygen is given off; for the peroxide, when its electric energy is concentrated towards one pole, by its entering into union with acids, lets go the particle of oxygen on the other, and thus passes to the state of an oxide, containing one particle of oxygen to a particle of metal. This oxide may be obtained by precipitation from its states of union, by exposing any other oxide mixed with charcoal, to a white heat, or by transmitting a current of hydrogen gas over it, when it is hot. Its atomic weight is 45 (351 manganese, 101 oxygen). It possesses a green colour, and is either permanent in the air, or rapidly unites with oxygen, according to the state of separation of its parts. They may

evidently unite among themselves into molecules, a convex pole of one occupying a concave pole of another; and thus, when they constitute axes among themselves, of considerable length, their affinity for oxygen must be very inconsiderable. If, again, they exist individually, an addition to the axis, which is very short, compared with the equatorial diameter, and a symmetrical form, may be speedily expected by the incidence of oxygen from the air, an effect which, in both cases, must speedily be effected, when the molecules are separated by heat, and both assimilated in their condition. In accordance with these views, we find that Forchhammer and Arfwerdson prepared this oxide of such a quality, that it took fire when heated, and, at an ordinary temperature, attracted oxygen from the air; while Professor Turner prepared one which had been in a molecular state, for it underwent no change for many days.

Brown Oxide. If, instead of oil of vitriol, heat only had been applied to the black oxide, oxygen in like manner had been disengaged, and in such proportion, as to indicate that every other particle of oxide had given off one of oxygen. After thus laying bare a pole, conformable to the pole of a particle charged with two of oxygen, one particle of peroxide, and one of protoxide, unite into one molecule; which is no longer decomposed by the heat, and the whole mass becomes an oxide, composed of two particles of manganese, and three of oxygen. In submitting to this change, the solid body ought to lose th part of its weight, for the weight of two particles of black oxide, is 110, and that of the resulting united oxide 100. But the weight of the vital air obtained, ought to amount toth of the original manganese used in consequence of the accession of weight, which oxygen receives on entering the gaseous state. It is said that the weight of the oxygen obtained is rather more than th, which may arise from the existence of some oxide containing a larger quantity of oxygen, or some irregularity in the experiment.