Imatges de pàgina
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Extract of a letter from M. Van Mons to Mr. Tilloch.
[From the Philosophical Magazine and Journal for January, 1815.3

SIR,

"You are probably acquainted with the new discoveries made at Milan, by Messrs. Moscati and Maury, relative to the sun, its diurnal or rotatory motion, its volcanos, &c. I send you a translation of the report published on this head; I also send you a note to what I have said on the metallo-fluores, and another on my new theory, which is that of caloric considered as a constituent part of all bodies containing oxygen, displaced in the combinations and displacing itself in the decombinations. Afterwards I admit hydrogen reduced into its gas into all the combustible bodies, and into the metals, and subsaturated in all bodies which can, in their quality of bases, contract combinations. Hydrogen gas is a simple body; oxygen gas is composed of equal parts of oxygen and of caloric: the primitive material of the globe, and without doubt the substance of the other planets, also consists of equal parts of oxygen and hydrogen, without the least quantity of caloric, which would break this relation: water is oxygen gas displaced in the ratio of from its caloric by two of hydrogen, and there result in this way 15 parts of oxygen, 13 of caloric, and 2 of hydrogen. The metals compose the primitive matter of the globe, with more or less hydrogen, and still without the least portion of caloric. The acidifiable combustibles are dry acids and hydrogen; the salifiable combustibles, or metallo-fluores, are an acid and the metals; the acidifiable burners (comburans) are dry acids and oxygen; the common acids are dry acids and water; and the dry acids themselves are peculiar combustibles in which the hydrogen is saturated by at least double the quantity of oxygen that it is in water; which may combine all the other bodies, but which cannot be put out of combination. All the other bodies are compounded of the latter. Water is decomposable by luminous caloric only; and when it oxidates bodies, it puts itself in the place of the equivalent of its contents in hydrogen, in the same way as, when hydrogen reduces bodies, it puts itself in the place of the water, I embrace the

whole domain of chemistry in this manner: Will you have the goodness to submit my ideas to the penetration of men of science in your country?

"M. Dobereiner, of Jena, not having found any soda which contained iodine, sought for this substance in sea water, where he found it. The intactile powder is iodate hyperoxygenated by ammonia, as detonating oil is muriate hyperoxygenated with the same alkali. The iodate of ammonia may be formed by simple oxygenation, whereas the muriate of ammonia requires to be hyperoxygenated.

"You will be soon made acquainted with an experiment in which muriate of ammonia, obtained by the combination of its gaseous elements, deposited all the water from its acid, taking up in its stead muriate of mercury and oxydule. This fact is decisive for the existence of oxygen in chlorine, and triumphant for Mr. Murray.

"You will also find that the Prussic acid gas, and water and alkohol impregnated with this gas, kill, in the most insignificant doses, and in three minutes, without convulsions, and as if a profound sleep had come on.

"I have ascertained that the essential oils which are distilled with alkohol or ether, cannot be again completely separated from those liquids, but retain at least the third of their weight: whether we attempt their precipitation by water, or try to make them float to the surface in the cold way.

"We have at Bruxelles a pile of Zamboni, which I have described in my French translation of Davy's Chemistry. It consists of disks of the diameter of a guinea, which are inclosed with pressure in two glass tubes of the form of columns. The substance of the disks is gilt paper sprinkled with native oxide of manganese, a vertical needle half a foot long, which is suspended about the sixth of its length towards the bottom, and oscillates between the two columns, striking at each half oscillation two bells with which the columns are surmounted. This movement, which is not much different in point of rapidity from the pendulum of a clock of the same length, has now existed for seven months: it is a true perpetual motion arising from a physical impulse. The circulation ascends this pile dry, and no chemical composition exhausts it.

VOL. V.

No. 20.

"There has been lately found in the calcareous stone of Chimaii, which is a blue bituminous shell-stone, a living toad of supernatural size. Has this animal been surprised in the formation of the stone, or has the stone generated it? It is conceivable that, by exclusion from the air, vitality might be only suspended, but then the substance of the stone must have nourished it to make it grow."

State of Medicine in China.

M. Page, a physician of Orleans in France, has published a work on this subject. The following short account of the Chinese medical practice will probably amuse some of our readers:

"The Chinese employ emetics and purgatives, but very rarely; clysters are almost never used, because they regard them as too European, but they make a free use of cordials. The importation of opium is prohibited under pain of death.

"The Chinese in the treatment of the itch and eruptive diseases employ camphor and cinnabar also, with sulphur dissolved in woman's milk. They make use of borax in inflammations of the throat; it is reduced into powder, and blown upon the diseased part. They borrowed the use of the bark from the Jesuit missionaries.

"They were acquainted with inoculation long before us. They practise it in general by introducing into one of the nostrils cotton imbibed with variolous matter: the cotton is allowed to remain twelve hours, and in seven days at latest the disease appears.

"Like most Indian nations, they make a free use of aphrodisiacs, baths and mineral waters. They have springs saturated with alum and iron, but the greater number contain sulphur. Their physicians are not able to analyse them. Chemistry as well as natural history is in its infancy in China. But the Chinese have the good fortune to possess a species of mesmerism or animal magnetism, as practised by certain sects of Illuminati in Germany. The Chinese literati strive to put down this sect by ridicule; but they nevertheless find proselytes daily, to what they are pleased to call the science of sciences.

"The Chinese are not acquainted with the making of bread, for which they substitute boiled rice or maize: their wine is a strong liquor extracted from honey or fermented rice. They do not drink either coffee or chocolate-they have delicious melons, the species of which is unknown to us, some very delicate kinds of small onions, and several delicious plants; but they have no olives, strawberries, gooseberries, or potatoes.

"The diseases of stone and gravel are wholly unknown to the Chinese-in consequence, as they tell us, of the great quantity of tea which they drink."*

Tannin.

M. Pelletier has published in the Annales de Chimie some observations with a view to show the imperfect state of our knowledge of this substance and its combinations with gallic acid. The various kinds of tannin which have been successively produced from various processes, are different in the greater part of their properties: they have nothing indeed in common, but the property of several animal substances, and forming with them insoluble combinations which are not susceptible of putrefaction, and have also the power of precipitating in a manner nearly similar even metallic solutions; but they are different in their taste, colour, solubility in water, &c. Pure tannin does not exist: the properties which are attributed to it, and by which it is characterized, belonged to several combinations which vegetable substances form. Why then, asks M. Pelletier, shall we continue to consider this as a distinct principle?

Is it because it precipitates several metallic oxides from their solution? Almost all vegetable extracts have the same property, and we know that these extracts are at least triple combinations of acid, the colouring substance, and of vegetoanima Imatter, because the precipitates which form the tannin matter in those solutions are constantly coloured and sometimes very brilliant. But if we reflect that gallic acid always accompanies tannin, and that the colours of the precipitates

The great consumption of tea in England is well known: are the affections arising from urinary calculi less frequent in that country? We may form some idea on this subject by reading the papers of Brande, Home, and Hatchett.-Note by the French Editors of the Annale de Chimie.

furnished by the tanning matter, and the metallic solutions, are the same with those manifested by the addition of the gallic acid, and the same metallic solutions; may we not conclude with M. Thenard, that the colouring of these precipitates is owing to the gallic acid, from which we can never entirely separate tannin? or is it the property which tannin has of combining with animal matter and preserving it from putridity? A multiplicity of combinations of vegetable matter also possess this property; and without mentioning the astringent matter formed by the action of mineral acids on charcoal and several vegetable substances, or the experiments of M. Chevreul on hematine (which acquired this property) and who disbelieves the existence of tannin, I shall mention some facts to prove that gallic acid can combine with several vegetable substances, and thus acquire the properties of tannin. If we put a solution of pure gelatine in gallic acid, no precipitate is formed: this acid does not produce any turbidness in the gummy solutions, but they cannot be resolved without immediately becoming turbid in white flakes which are soon precipitated. Among the pharmaceutical extracts there is a great number which do not contain the astringent principle, and which form no precipitate in the solution of gelatine; but by the addition of gallic acid they acquire this property. The same phænomenon does not take place with the other vegetable acids, which on the contrary seem to oppose themselves to the precipitation of gelatine.

We know that pure gallic acid forms no precipitate in a solution of sulphate of iron at the maximum, but it there becomes a beautiful deep-blue colour. Infusion of nut-galls produces, on the contrary, a precipitate which is attributed to tannin; but gallic acid of itself acquires the property of partly precipitating the iron from this solution when it is combined with extractive matter: most of the vegetable infusions unite with gallic acid and gelatine, the same as the extractive substances, for which we can assign no reason. The phenomenon is very perceptible with the cold infusion of saffron: the properties of these precipitates cannot be absolutely identical; they must differ according to the nature of the substances which enter into each combination: that formed by gum arabic, gelatine and gallic acid is the only one which I have hitherto been able to exa

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