and gives products containing oxygen, hydrogen, and charcoal as their elements. It combines with bases, and forms salts. Those of potash, soda, and ammonia, are very soluble: the rest are nearly insoluble.

17. Metallic Manganese.

The properties of metallic manganese, reduced by M. Fischer. of Schaffouse, are described in the Bibliothèque Universelle as follows:-The fracture is neither conchoidal nor crystallized, but irregular, and very similar to that of the sulphuret of iron, commonly called marcasite. The metal is of a white colour. It is harder than tempered steel, and cuts glass almost as well as the diamond. It is capable of scratching rock crystal. It takes a very fine polish, but the permanency is doubtful, in consequence of its affinity for oxygen. Placed in water for 24 hours, it becomes covered with a brown oxide. It acts sensibly on the magnetic needle, perhaps in consequence of a little iron. The specific gravity is 7.467.

18. Analysis of Bitter Almonds.

M. Vogel, in his experiments on and analysis of bitter almonds, gives the following proportions of the substances in 100 parts.

The essential oil appears to be a very singular substance. It is best obtained by distilling almond water with barytes, to separate the prussic acid. In close vessels it is very volatile; exposed to the air, it becomes solid, crystalline, inodorous, and of considerable fixity. The crystals are a compound of it with oxygen, for oxygen is absorbed during their formation, and if they are dissolved in hydro-sulphuret of ammonia, they are again decomposed, and the original odour and oil is produced.

19. Venom of the Common Toad.

M. Pelletier has given the following account of the venom of the common toad.

The fluid which in the common toad is contained in the vesicles which cover the skin is of a yellow colour, and an oily consistence. Exposed to the air, it soon becomes concrete, and if it be received upon a plate of glass it can be raised in the form of solid transparent scales after a few seconds. The venom of the toad, whether in the solid or the liquid form, is extremely bitter, acrid, and even caustic, it reddens strongly the tincture of litmus, and forms an emulsion with water. Cold alcohol scarcely acts upon it, but when hot it attacks and dissolves a part, and acquires a fawn colour. The portion undissolved in the alcohol is perfectly white, without odour or taste, and resembles gelatinous membrane.

The alcoholic solution scarcely reddens litmus, and even loses that property entirely by evaporation. As the alcohol is disengaged a fat oily matter separates, which concretes on cooling, is insoluble in water, a little soluble in ether, but much more so in alcohol. Taste bitter, but neither acrid nor caustic. Instead of reddening litmus it restores the blue colour if it has previously been changed by an acid. These phenomena seem to indicate: 1st, that the acid of the venom is volatile; 2nd, that it is partly saturated by a base to which it loosely adheres, and from which it may be separated by other acids.

The gelatinous matter insoluble in alcohol, dissolves in hot water, but not in cold. The solution on cooling becomes opalescent, and has a degree of consistency. The substance which might at first be taken for gelatine is proved by comparative experiments to be distinct from it. It is not precipitated either by solution of chlorine or infusion of galls.

It may be concluded that the venom of the toad contains 1, an acid partly united to a base, and constituting about onetwentieth part of the whole; 2, a bitter fatty matter; 3, an animal substance having some analogy to gelatine, but differing from it in certain points.

20. Ignited Wire Lamp.

Sir H. Davy in his researches on flame, ascertained a peculiar state of combustion at a heat below that of flame, and he rendered the phenomenon evident by causing it to take place round a platinum wire, which became and remained ignited, in consequence of the heat given out. The effect was shewn to be produced either by platinum or palladium wires, in atmospheres made explosive either by mixture with inflammable gases or the vapour of inflammable substance, as ether at common temperature, or warm spirits of turpentine, alcohol, &c. The experiment has lately been very ingeniously varied by making the heated wire volatilize the alcohol. A coil of platinum wire about the of an inch in thickness, and containing from 8 to 15 or 16 turns, is dropped on to the wick of a spirit lamp, so that part touches the wick and part remains supported above. On blowing out the flame of the lamp after it has been lighted, the wire will become ignited, and continue so as long as any spirit remains below.

It has been ascertained that camphor may be substituted for the alcohol, by introducing a cylinder of it in the place of the wick; the ignition is very bright and a pleasant odorous vapour arises from it. Oil of turpentine in the lamp also succeeds. The wire does not remain ignited, but the continuance of the effect is marked by the ascent of a dense line of vapour, which rises from the wire, and diffuses an odour by some thought agreeable.

By adding essential oils to the spirit or oil of turpentine below, it is probable that various aromatic odours might be obtained, and the lamp would perhaps replace the fumigating pastiles which are used for this purpose. In some trials of this kind, the wire was found to become covered with a coat of charcoal after some time, and then the effect ceases, but this could easily be burnt off by a spirit lamp.

21. Changes of Colour by Heat.

Change of colour dependant upon temperature alone, is a com mon phenomenon in chemistry. Several instances have been

given in the Annales de Chimie, by Gay Lussac. The following are some others.

Nitrous acid gas has its red colour very much heightened by heat; on cooling, it returns to its first appearance.

White oxide of zinc obtained by combustion becomes yellow when beated, but returns to white when cooled.

Red oxide of mercury obtained by heat from the nitrate, has its colour increased by heat, and diminished by cooling.

Red oxide of iron, prepared by heating the precipitate from green vitriol by an alkali, becomes dark brown or nearly black by heat, and on cooling, resumes its light red colour. Common red oxide also changes in the same way, but not so much.

Borax tinged emerald green by fusion with chromate of lead, becomes a fine brown when heated, and returns to its original green colour when cold.

White oxide of titanium heated, becomes lemon yellow; cooled, it returns to white.

Chloride of silver, when fused and cold, is transparent and colourless, if heated, it becomes brown, then deep reddish brown, and almost opaque; on cooling it retrogrades through the various shades it had taken, and resumes its original appearance.

An infusion of red cabbage, when cold, is of a fine blue colour; when heated, it becomes red or rather purplish, but on cooling, resumes its blue tint; and these changes may be repeated continually. If a similar infusion be rendered slightly green by a little alkali, the affect of heat is sufficient to counterbalance the influence of the alkali and the infusion appears blue; on cooling, the green colour which it resumes shews the alkali present. If a hot and a cold infusion of red cabbage be rendered similar in colour, by the addition of a little alkali to the former, they appear exactly alike by transmitted day-light, but transmitted fire or candle-light, makes the former appear red, and the latter greenish blue. A similar difference is observable in the two solutions prepared by dissolving oxide of nickel in ammonia, and by adding ammonia in excess to the nitrate of nickel; they are both VOL. V.

K

of a fine blue colour by transmitted day-light, but transmitted artificial light renders the latter red, though it does not alter the former.

22. Babylonian Cement.

A substance, said to be part of the walls of a Babylonian structure, has been analyzed by M. Vauquelin, and gave the following

It was of a dark brown colour, of a bituminous appearance, but so hard as to resist the hammer; part of its surface was irregular, but smooth, and of a vitreous appearance; and it is supposed to have been a cement applied in the soft state but dried by heat. The quantity of oxide of iron is remarkable.

23. On Chemical Nomenclature.

The Society of Arts and Sciences at Utrecht, proposes the following prize question, to be decided on the 1st of October, 1818, fixing either a gold medal worth 30 ducats, or the same sum in cash, if preferred, for the best treatise written in either the Dutch, German, English, French, or Latin language, and sent in time, post paid, to the Secretary, Professor Rossyn, at Utrecht.

"Is the chemical nomenclature, as proposed by the famous Lavosier and his collaborators, and as has been afterwards adopted, with few alterations, by almost all chemists, such as is still satisfactory with regard to its principal characteristics, or do the modern discoveries, particularly those made in consequence