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furnished with feet, for then there is more space for the fluid. A series of glass receivers, contracted at top in the usual way, form the other part of the apparatus. Their number and size is to be such, that one will go between each glass jar, and they are to be connected together by the necks air tight, in a way that, when put down among the glass jars, each shall take its proper place; a trumpet-formed tube is to be fixed in the midst of these receivers, its wide termination being destined for the inner jar, and the narrow end to pass upwards through the necks of the receivers, and to form the only aperture through them; on this is fixed globular receiver, to which a retort generating gas or any other apparatus, may be fixed. When used, as for instance in the production of muriatic acid, water is put into the jars, and the receivers dropped down until their edges dip some way into the water, then muriatic acid gas being made to enter above, any impurities it carries over are deposited in the balloon, and the gas passes down the trumpet tube, and is absorbed by the fluid beneath. When that portion of the fluid is saturated, the gas by its pressure depresses the solution, and escaping into the first receiver, gets round

the edge of the jar, and comes in contact with the water on its outside in the second jar; it becomes also saturated, and then the gas passes into the second receiver, and so on.

The form and the shape of this apparatus are easily varied, they have been made of porcelain and stone ware, they have also been made square and oblong. Dr. Hare, has found them so effectual as to produce a strong solution of muriatic acid in the central jar, when the fluid in the third and external jar has not been at all acid.-Silliman's Journal, Vol. I. p. 410.

25. New Method of preparing the Purple of Cassius.-The Count de Maistre says, that placing a sequin in contact with mercury at one of its surfaces, and twenty-four hours after

fusing it with an equal weight of tin, an alloy was obtained, which was fusible in boiling resin. Afterwards triturating this alloy with pure caustic magnesia in a mortar, a powder was obtained of a very fine purple colour.

26. Fulminating Gold.-Count de Maistre also describes a fulminating gold obtained by pouring a small quantity of solution of gold into red wine, (Bordeaux); a sediment formed which, when dried, and placed on burning charcoal in an iron capsule, exploded.

27. Soda alum.-An alum, containing soda as its alkaline base, has been sent to the Royal Institution, by Mr. Beatson, who states that it is decomposed, when in solution, by cold, which causes the separation of crystals of sulphate of soda. It is decomposed also by salts of potassium, which separate from it crystals of common alum. A hasty analysis of it, made in the laboratory, gave, in 100 parts of this alum, 51.2 of water, 32.14 sulphuric acid, 10 alumina, and 6.32 of soda;

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This gives 2 proportionals of sulphate of alumine, 1 proportional of bi-sulphate of soda, and 28 proportionals nearly of water; hence its composition seems to be very analogous to that of common alum, as ascertained by 'Mr. Phillips.

It crystallizes in octoëdra, which are generally very imperfect. (See Journal, page 363, Vol. VI.)

M. F.

28. On the conversion of Ligneous matter into Gum, Sugar, a particular Acid, and Ulmin.—M. Braconnot's researches on these substances are of extreme importance, from the relation they have to the conversion and formation of the same principles by natural processes. The following is a compressed account of his Memoir, which has just reached this country.

Whilst examining the action of sulphuric acid on wood, 20 grammes (308.9 gr.) of dried elm saw-dust were moistened

with cold sulphuric acid, of sp. gr. 1.827, and the mixture stirred; it heated, and much sulphurous acid gas was disengaged. The wood became black, and appeared to be charcoal, 'but was not so in reality. Water was poured on the mixture, and the black powder separated; when dry, it burned with flame. It did not colour cold water, but with boiling water and alkaline solutions gave a deep brown solution. It was nearly in the state which the saw-dust would have acquired by exposure for some years to air and moisture. The nearly colourless acid liquor, after being saturated with carbonate of lime, gave on evaporation, a yellow gummy matter, with a solution of which sub-acetate of lead formed an abundant white magma. The gummy matter, acted on by weak sulphuric acid, gave acetic acid, and a precipitate of sulphate of lime.

The experiment was repeated, with 16 grammes (247.1 gr.) of the saw-dust; but instead of mixing the whole quantity of materials at once, small portions of the wood were triturated at a time, adding the acid by degrees; still sulphurous acid was disengaged, but a very thick tenacious mucilage was obtained. This was diffused in water, and filtered through a cloth; there remained a black insoluble matter, weighing 5 grammes (77.2 gr.) similar to that before-mentioned. The acid liquor, saturated with chalk, and then evaporated, gave 10 grammes (154.5 gr.) of a substance of a reddish brown colour.

As MM. Fourcroy and Vauquelin state, that vegetable substances do not decompose sulphuric acid when cold, M. Braconnot sought some other ligneous substance that would not produce this effect, and ultimately selected hempen cloth; 25 grammes (386.1 gr.) of this cloth, in small pieces, lost on drying 1 gramme (15.5 gr.) of water. It was moistened in a glass mortar, with 34 grammes (525) of sulphuric acid added by portions, and continually stirred with a strong rod of glass, that the acid might penetrate all parts, and that the heat caused by each addition of it, might be dissipated before more acid was added; not the slightest portion of sulphurous acid was disengaged. A quarter of an hour after the mixture was made, it was rubbed in the mortar; the tissue of the cloth disappeared, and a very tenacious mucilage, homogeneous, and little coloured, was obtained

This was left for twenty-four hours, and was then entirely soluble in water, with the exception of an amylacious matter, weighing, when dry, 2.5 grammes (38.6 gr.). It was a portion of the cloth not perfectly altered by the acid. The diluted acid mucilage was saturated with chalk, and filtered through cloth, it was then clear, and of a slight amber colour. After washing the filter well, and pressing strongly the sulphate of lime, all the liquors were united, and evaporated to a syrup, which was less coloured than that of capillaire. A small quantity of sulphate of lime separated on cooling. The evaporation being continued to dryness, a slightly coloured transparent gum was obtained; it weighed 26.2 grammes (404.6 gr.), and was produced from 21.5 grammes (332 gr.) of cloth, abstracting the one gramme of water, and the 2.5 grammes (38.6 gr.) of amylacious ligneous matter. The sulphate of lime also retained a portion of vegetable matter, for it blackened, &c. on being heated. To ascertain whether this increase of weight was due to the fixation of the elements of water, or sulphuric acid, five grammes (77.2 gr.) of the gum were dissolved in water and oxalic acid added to them. The precipitate collected, and strongly heated, gave,28 grammes (4.3 gr.) of lime. The solution then evaporated to dryness was treated with boiling nitric acid, and diluted with water; nitrate of barytes then gave a precipitate, which, heated red, gave 1.6 grammes (24.7 gr.), equivalent to ,54 grammes (8.34 gr.) of sulphuric acid. As no aeriform matter was disengaged during the action of the acid on the cloth, the 26.2 grammes (404.6 gr.) of gum may be supposed to be thus constituted.

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Hence it appears probable, that the heat evolved during the action of sulphuric acid on vegetable substances is occasioned by the fixation of the elements of the acid and of water,

When the sulphuric acid was diluted with half its weight of water, it had no action on the linen, cold; but heated, it formed a homogeneous paste, which, mixed with water, resembled boiled starch; farther diluted, it appeared like an emulsion. When observed in the sun, a number of brilliant scales were seen in it, as in a solution of soap. By standing, it deposited a substance resembling starch in appearance, but not having its properties. The liquor separated, gave a very small quantity of gum.

If the cloth be moistened with nitric acid, there is no alteration at common temperatures, but exposed to a hot-water bath until nitrous gas begins to form, it is converted into a white and uniform paste exactly like that obtained by the sulphuric acid. Washed and dried, it had a satin appearance, especially when reduced to powder; if moistened, a slight hissing was. heard, and it formed a paste. It is not soluble in potash, and appears to be the ligneous matter of the linen very slightly altered.

The gum obtained by the action of sulphuric acid on linen was purified by precipitating it by sub acetate of lead, and decomposing this compound by sulphuric acid. The liquid was evaporated to a sufficient degree, and the sulphate of lead being separated, the gum was thrown down by alcohol. The sulphuric acid it retained was separated by heating it with oxide of lead, and the small quantity of lead still retained in solution, then separated by sulphuretted hydrogen: the filtered liquor being evaporated, the gum was obtained as pure as possible.

The gum then resembled gum-arabic. It was transparent, of a slight yellow colour, inodorous, insipid, though it reddened tincture of turnsole, and appeared to behave like an acid. The fracture was vitreous. It adhered strongly to the vessels in which it was evaporated, and formed on them a shining kind of varnish. It formed a mucilage less tenacious than that of gum-arabic. Heated, it burnt, giving out a strong odour of sulphurous acid, occasioned by the presence of sulphuric acid in such a state of combination as to be incapable

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