4. Iodous Acid.

Il Sig. Sementini, of Naples, has published an account of a combination of iodine and oxygen, containing less of the latter principle than iodic acid. It is obtained in the following manner: Equal parts of chlorate of potash and iodine are to be triturated together in a glass or porcelain mortar, until they form a very fine pulverulent yellow mass, in which the metallic aspect of the iodine has entirely disappeared. If there be excess of iodine, the mixture will have a lead colour. This mixture is to be put into a retort, the neck being preserved clean, and a receiver is to be attached with a tube passing to the pneumatic trough. Heat is then to be applied, and for this purpose a spirit lamp will be found sufficient; at first a few violet vapours rise, but as soon as the chlorate begins to lose oxygen, dense yellow fumes will appear, which will be condensed in the neck of the retort into a yellow liquid, and run in drops into the receiver; oxygen gas will at the same time come over. When the vapour ceases to rise, the process is finished, and the iodous acid obtained will have the following properties :

Its colour is yellow, its taste acid and astringent, and leaving a burning sensation on the tongue. It is of an oily consistency, and flows with difficulty. It is heavier than water, sinking in it. It has a particular odour, disagreeable, and something resembling that of euchlorine. It permanently reddens vegetable blues, but does not destroy them as chloric acid does. It is very soluble in water and alcohol, producing amber-coloured solutions. It evaporates slowly, and entirely in the air. At 112° Fahr. it volatilizes rapidly, forming the dense vapour before mentioned. It is decomposed by sulphur, disengaging a little heat, and liberating violet vapours. Carbon has no action on it at any temperature. Solution of sulphurous acid decomposes it as well as iodic acid, precipitating the iodine as a brown powder. It is characterized by the manner in which potassium and phosphorus act on it: the instant they touch it they inflame; the potassium producing a white flame and dense vapours, but little or no liberation of iodine, and the phosphorus, with a noise as of ebullition, violent vapours appearing at the same time.

The odorous nature of this acid, its volatility, colour, and its power of inflaming phosphorus by mere contact, show that some of the principal characters of iodine are retained, and that it is oxygenated, therefore, in a minor degree, and deserves the name of iodous acid.

Its composition has not been experimentally ascertained. M. Sementini endeavoured to analyze it by putting 100 grains into the end of a long sealed tube, and then dropping a small piece of phosphorus in, iodine was disengaged, and condensed in the upper part of the tube, and this was found to amount to 45 grains; but this can furnish only very uncertain results.

Iodous acid dissolves iodine, becoming of a deep colour, more dense and tenacious, and having more strongly the odour o iodine. When heated, the iodine partially rises from the iodous acid, but they cannot be separated in this way.

M. Sementini believes also in an oxide of iodine, and has given the name to the black powder, which is produced by the action of sulphurous acid on iodous acid, and which still contains gen, but he mentions that this and some other points still require investigation.

oxy

The following are the properties of the iodic and iodous acids, by which a judgment may be formed of their specific difference. Lodic acid is solid, white, without odour, reddening blue colours, and then destroying them. Volatile at 456° Fahr. with decomposition; heated with charcoal or sulphur, it is decomposed with detonation. Iodous acid is liquid, yellow, odorous, reddening blue colours, but not destroying them; volatilizing at 112° Fahr. and even at common temperatures without decomposition; heated with sulphur it is decomposed without detonation, and inflames potassium and phosphorus by mere contact. Bib. Univ. xxv. 119.--(Journal of Science.)

5. Inflammation of a Mixture of Oxygen and Hydrogen under Water.

1

Every one is acquainted with the oxyhydrogen blowpipe. Mr. Skidmore, of New York, has observed that the luminous jet obtained with that instrument may be introduced under water, without being extinguished. The only precaution necessary is to introduce it slowly, that the flame may not be repelled into the receiver.

The flame viewed under water is globular. It burns wood, and heats metallic wires to redness. Mr. Skidmore thinks that his observation may be advantageously employed in maritime warfare.

6. Advantageous Mode of using Alcohol in Vegetable Analysis.

MM. H. Petroz and Robinet, in their examination of the fruit of the lilas, treated the decoction of the grains with a large quantity of alcohol gradually added while in the state of a thick syrup, without reducing it to a further degree of dryness. By this mode the product of the decoction is at once divided into two portions, one soluble in alcohol, the other not. The decoction should not be evaporated to a very thick syrup, for in that case the precipitated matter retains some of the substances which should be taken up by the spirit. The alcohol must be of such a strength as not to be too much weakened by the water remaining in the syrup.-(Journal de Pharmacie.)

MINERALOGY.

7. Garnet.

To the numerous analyses which have already been published of the individuals belonging to this important class of minerals, we have to add the following:

1. Green trapezoidal garnet from the mine Gamla, in Sala. Sp. gr. 3-746.

2. The same, from the same locality, but obtained at a differ

(Bredberg, Kongl. Vet. Acad. Handl. 1822, p. 83.)

3. Calcareous garnet, from Lindbo, in Westmannland. Colour, black and blackish brown. Crystal, the primitive rhomboid, sometimes with truncated lateral edges.

These three analyses accord sufficiently with the formula which has been deduced as representative of the constitution of garnet; namely, an atom of a silicate of a base containing two atoms of oxygen + an atom of a silicate of a base containing three atoms of oxygen.

1. The mineralogical formula for the Sala garnet is

mg

} }S + FS

It is greatly to be wished that this extensive genus were subjected to a more systematic examination than it has hitherto received, and as has already been done so successfully in the case of the pyroxenes and amphiboles. The accuracy of the preceding formula is indeed supported by strong arguments; but many, particularly of the older analyses, are contradictory of it, and the simplicity of the crystalline form of garnet renders peculiarly necessary a severe induction of facts, before it can be regarded as demonstrated that there are not at present confounded under this name several genera of minerals, which are essentially distinct from one another, even on the broad basis of the isomorphous theory.

8. On Meionite.

Our mineralogical readers are aware that within these few years analyses of this mineral have been successively published by Arfwedson, Gmelin, and Stromeyer. The results of the last two chemists were almost identical; but those of Arfwedson disagreed with both so materially, that it was obvious that either he or they must have been engaged with a different mineral from meionite. M. Arfwedson, in a letter to Schweigger, acknowledges his mistake, and states, that on repeating the analysis with an authentic specimen, he had obtained results which indicated exactly the same formula with those of Gmelin and Stromeyer. It is singular that the mineral which he originally analyzed, although scarcely differing in composition from leucite, was easily fusible before the blowpipe; whereas leucite is quite infusible.-(Jahrbuch der Chemie und Physik, ix. 347.)

9. Erlanite, a new Mineral.

Lustre, feebly shining to dull. Streak shining, with a fatty lustre. Colour, light greenish grey: streak, white. Massive. Sometimes compact, sometimes in small and fine granular distinct concretions. Fracture in some specimens foliated, in others splintery and even. Its structure is distinctly crystalline, but no specimen has yet been observed which admitted of regular cleavages. Hardness, between that of apatite and actynolite. Sp. gr. from 3.0 to 3.1. Before the blowpipe, it melts easily into a slightly coloured, transparent, compact pearl, and resembles gehlenite more closely than any other known mineral: from felspar it is distinguished by its greater sp. gr.; from Saussurite, by its inferior sp. gr. and hardness. 1d emote a u

It was discovered in 1818 by Briethaupt in different parts of the Saxon Erzgebirge. It forms a part of the oldest gneiss formation, and is always mixed with more or less mica. Between Gros-Pöhle and Erla there exists a bed of it at least 100 fathoms in thickness. It has been used for upwards of 200 years as a

flux by the iron smelters, and until its examination by Briethaupt, it had been uniformly mistaken for limestone. 124 According to the analysis of Prof. C. G. Gmelin, it is composed of

(Schweigger and Meinecke's Jahrbuch der Chemie und Physik,

vii. 76.)

10. Native Compounds of the Oxides of Uranium and Sulphuric

Acid.

These new mineral bodies, alluded to by Berzelius, are thus described by Prof. John, their discoverer.

(1.) Sulphate of Oxidule of Uranium.-It always occurs crystallized, and most commonly in flattened prisms, from one to three lines in length, which are arranged in eccentric druses. Colour, beautiful emerald green, sometimes passing into apple green. Lustre considerable, glassy. Transparent; sometimes, also, opaque and dull. Brittle, and easily pounded. Soluble in water. The solution is precipitated chesnut brown by the triple prussiate of potash, yellowish green by alkalies, and in brown flocks by infusion of nutgalls. Nitrate of silver and metallic iron occasion no alteration; and a solution of barytes precipitates a white powder, insoluble in nitric acid. When ignited, it undergoes partial decomposition; for if, after this treatment, it be digested in water, a yellow coloured powder remains undissolved. It accompanies the following mineral, which had heretofore been erroneously regarded as an oxide of uranium.

(2.) Subsulphate of Oxide of Uranium.-It forms a thin, botryoidal, intense sulphur-yellow coloured coating over the surface of the minerals on which it is found. It is friable, and soils the fingers. Digested in water, a portion of it passes into solution. The residue dissolves in nitric acid; and both solutions possess the properties of a solution of sulphate of oxide of

uranium.

Both minerals occur in Elias's mine, at the distance of about a league from Joachimsthal, in Bohemia.

The examination of these compounds, observes Dr. John,