time, one with the air removed, the other containing air at the ordinary pressure of the atmosphere; the graduation of the last remained accurate after several months, whilst the zero of the first rose nearly a half degree. The bulb of the altered thermometer was so thick, that no effect due to atmospheric pressure acting from without inwards could be supposed a circumstance which excludes the explanation of the effect adopted by MM. Bellani and Flaugergues.

M. Arago concludes by observing that it may perhaps be found preferable to boil the mercury so well as to exclude all air from it; but states that from certain experiments made by M. Dulong, and not as yet published, it would appear that the precautions necessary are so minute and numerous, that the instrument-maker will find it a difficult matter to construct a thermometer of that kind that will not change its zero.-Annales de Chimie, xxxiii. 423.

7. On Bromine and certain of its compounds, by M. Serullas.— According to M. Balard, bromine remained fluid at a temperature so low as 0° Fahr. M. Serullas found that a degree or two below this it suddenly became solid, and was then hard, and so brittle as to break by a blow.

On adding hydriodide of carbon to bromine in a tube, there was immediate action, much heat, a hissing noise, and a bromide of iodine and a fluid hydro-carburet of bromine were formed;—a further instance this, of the displacement of iodine by brome. Water dissolved the bromide of iodine, and the hydro-carburet with a little excess of bromine remained at the bottom of the fluid. It was rendered colourless by a little alkali. If the hydriodide of carbon is in excess, but little hydro-carburet of bromine is produced, but a sub-bromide of iodine.

The pure hydro-bromide of carbon is colourless, heavier than water, of a penetrating ethereal odour, an exceedingly sweet taste, and very volatile. It does not become coloured in the air like the hydriodide of carbon, and when dropped on ignited porcelain it yields white vapours instead of violet. The same compound was formed by placing a drop of bromine in olefiant gas. When this substance is cooled to about 22° Fahr., it becomes solid, and then breaks in the manner of camphor.

M. Serullas formed hydro-bromic ether by putting forty parts of concentrated alcohol into a retort with one part of phosphorus, and afterwards adding, in small portions, seven or eight parts of bromine; upon each addition there was much action upon the phosphorus; heat was evolved, and hydro-bromic and phosphorus acids produced. Then carefully distilling the mixture, and washing the product with water, the hydro-bromic ether was collected at the bottom. It appeared as a colourless, transparent fluid, heavier than water, with a strong and etherial odour, and a sharp taste; it is very volatile, is soluble in alcohol, but is precipitated by water; it suffers no change of colour

Cyanide of Bromine.-Two parts of dry cyanuret of mercury are to be placed in a tubulated retort, or at the bottom of a long tube, and being well cooled in a refrigerating mixture, one part of bromine is to be added; powerful action ensues, with much development of heat, and a bromide of mercury with a cyanide of bromine are formed: the latter crystallizes in long needles about the middle of the tube, the small quantity of vapour of bromine gradually disappearing. A small receiver being then attached to the tube, and well cooled, the cyanide is to be sublimed into it, and will form small colourless, transparent crystals, sometimes acicular, sometimes cubical. This substance is very volatile, and has a penetrating odour; it becomes vapour at 60° Fahr., and crystallises suddenly by cooling. It is soluble in alcohol and water. Caustic alkalies produce a hydro-cyanate and a hydro-bromate.

The cyanide of bromine is excessively deleterious; a grain dissolved in water, and introduced into the œsophagus of a rabbit caused death as instantly as prussic acid would have done. All attempts to decompose bromine by acting upon it in this compound failed.-Annales de Chimie, xxxiv. 95.

8. On Oxide of Iodine and Iodous Acid, by Signor Sementini.— When Sementini first obtained iodous acid *, it was by heating a mixture of equal parts of iodine and chlorate of potash; but the latter salt not being pure, variable results were obtained. He then mixed iodine with chlorate of potash in a mortar, adding the former until a clear yellow colour was produced. Upon heating this mixture, yellow vapours appeared at first, which condensing on the neck of the retort used, did not redden the tincture of litmus ; but continuing the operation, a dense oleaginous fluid was obtained, reddening litmus, which, exposed to air, first absorbed a little moisture, and then was volatilized; having a very pungent, unpleasant and slightly acrid taste, and being decomposed by phosphorus, sodium, and potassium at common temperature, with the evolution of vapours of iodine.

In the operation referred to, it appeared that the first portion of iodine and oxygen combined to form a new compound oxide of iodine; that afterwards the action of the heat caused the combination of a larger proportion of oxygen with the iodine, and produced two new compounds,-the iodous acid, which, being volatile at a moderate temperature, was condensed in the neck of the retort; and iodic acid, which remained combined with the potash of the chlorate decomposed; a small portion of chlorine being at the same time set free, and rendering the last portions of iodous acid impure by its presence.

In consequence of these actions, the following method of preparing iodous acid is preferable to that first published, as supplying

* Quarterly Journal of Science, vol. xvii, p. 381.

it in a purer state, and in greater abundance. Chlorate of potassa is to be placed in a retort, with rather a large neck, and heated until the moisture is dissipated; then, at the time when oxygen is freely evolved from the salt, iodine is to be introduced by means of a metallic spoon as far as the body of the retort. The vapours of iodine which will be occasioned by the heat will immediately disappear, in consequence of their combination with the oxygen of the chlorate, and a strong effervescence will be perceived in the latter, occasioned by each portion of iodine with which it may combine; immediately yellow vapours will be perceived in the neck of the retort, and when they redden litmus paper, and a sufficient quantity of iodous acid has been obtained, the operation is to be finished, and the acid collected, the last portion being removed by a drop or two of water.

All attempts to unite this acid with alkaline bases have failed, the iodine being precipitated; this happens equally with ammonia, potassa, and soda, the attraction between the elements of the acid being so weak as to allow of their complete separation on these occasions.

Oxide of Iodine was discovered in attempts to combine iodine and oxygen directly together. It is to be obtained in the following manner. A copper tube about two palms (20.6 inches) in length, and eight lines in diameter, having one extremity terminated in a screw, and the other by a small aperture about a line in diameter, was fixed upon two supports; the contracted extremity was curved, so as to permit of its introduction into the tubular of a retort, without deranging its convenient inclination. A bladder filled with oxygen gas was attached to the screw. A long spirit-lamp with several wicks was placed beneath the lower part of the tube, so as, when necessary, to raise it to redness. Arrangements were also made for applying a lamp to the bottom of the retort, to elevate its temperature, it having been found that to combine oxygen and iodine, both should be at a high heat.

The tube and the retort being heated to redness, one person then presses the bladder to force heated oxygen into the retort, and another introduces a spoonful of iodine through the neck of the retort until it is brought under the jet of gas. The iodine is quickly converted into violet vapour, which fills the retort, but this soon disappears, and the retort neck becomes lined with a yellow transparent substance, almost solid; which, by the continuance of the operation, becomes more fluid, and flows forward as an oleaginous liquid. If the violet vapours are too abundant, the spoon is to be withdrawn for a little while, the introduction of oxygen being continued; when they have disappeared the iodine is to be re-advanced.

The substance obtained in the commencement of this operation, is oxide of iodine. It is of the consistence of a solid oil, has an acrid, disgusting taste, an odour similar to that of iodous acid, but

weaker. It is slowly dissipated in the air, is very soluble in water and alcohol, producing amber-coloured solutions. If brought, in the solid state, into contact with a dry, combustible substance, it is decomposed, iodine being evolved. Phosphorus and potassium are inflamed by it. It changes the blue litmus infusion to green. If an alkali be poured into its solution, the latter is instantly rendered colourless; whereas if alkali be added to solution of iodous acid, iodine is precipitated. The discoloration is due to the combination of the alkali with the iodine which is taken from the compound, a further proof of the weakness of the affinity between oxygen and iodine.

If the addition of oxygen be continued after the formation of the oxide of iodine, then iodous acid is formed; and, if the lamp applied to the bottom of the retort be at the same time removed to the neck, the formation of the iodous acid will be much facilitated.

Finally, oxide of iodine is always formed when iodine is heated in close vessels containing air, and air may be used in place of oxygen in the process above described. If iodine be put into a retort, and then a second be sealed hermetically to the first, a small capillary hole being left in the neck; the iodine being heated successively, first in one part and then in another of the apparatus, wherever it assumes the solid form, will gradually change into oxide of iodine.-Giornale de Fisica, ix. p. 387.

9. Quantity of Charcoal obtained from Wood.-The following table contains the results obtained by M. Karsten from one hundred parts of the shavings of woods which had been carefully dried in the air. Two modes of carbonization were used; the one rapid and commencing with a high temperature, the other slow and gradual. The quantity of ashes was obtained by incineration of the charcoal under a muffle.

10. Preparation of Cyanide of Iodine, by M. Serullas.-Place a large glass jar with its mouth upon a plate of glass: mix two parts of cyanide of mercury with one part of iodine, and heat the mixture in a small porcelain capsule until the temperature being sufficiently raised, the cyanide begins to form; then quickly place it under the jar, and leave the operation to itself; the production of cyanide of iodine will continue for fifteen or twenty minutes, presenting the appearance of a multitude of snow-white flocculi, of the utmost degree of whiteness and beauty: these will gradually collect on the plate, and may be afterwards secured.— Annales de Chimie, xxxiv. p. 100.

11. On the Detection of Hydrocyanic Acid in the bodies of Animals poisoned by it, by MM. Lassaigne and Leuret.—The extreme delicacy of the test employed by M. Lassaigne to detect prussic acid in the bodies of poisoned animals, namely, by means of the persulphate of iron, or the per-sulphate of copper, has been pointed out at page 397 of vol. xviii. of the former series of this Journal. Being desirous of ascertaining after how long a period the poison might be discovered, MM. Lassaigne and Leuret made experiments in which animals were killed by hydrocyanic acid introduced into their food, or thrown into the stomach in a diluted state, the dose never surpassing more than the equivalent of five or six drops of the pure acid, or less than two drops; the animals were left after death for twenty-four hours in a chamber, and then buried in moist earth a foot and a-half or two feet deep.

The disinterment took place after various periods, from fifteen days to a month, and the stomach and first portions of intestines being separated, were well divided and mixed with pure water, and distilled; a little sulphuric acid was added to the substances in the alembic, and the recipient was cooled by ice and water.

The products were rendered slightly alkaline, and then tested by the per-sulphate of iron or sulphate of copper, and a little excess muriatic acid was poured upon the precipitates occasioned by these salts. No prussic acid could be discovered in animals, the viscera of which were in a state of complete putrefaction; it was found after intervals of two or three days, but never after a longer period than eight days.