Images de page
PDF
ePub

acid, and the liquor is decanted off. It will be found to contain all the oxygen coming from the two portions of deutoxide of barium on which the operation was performed.

It is worthy of remark, that the same acid may be oxygenized several times repeatedly by the same process. I have oxygenized it as often as seven times.

Do these sorts of combinations take place in definite or indefinite proportions ? This must be ascertained by future experiments.

Be this as it may, when an excess of barytes water is poured into oxygenized nitric or muriatic acid, or into these acids

superoxygenized, a crystalline precipitate of deutoxide of barium falls. This precipitate is very abundant; it has the form of pearly scales, and is but little soluble in water. This liquid, at the temperature of 50°, decomposes it, and converts it into oxygen gas and barytes, or protoxide of barium.

Strontian and lime are susceptible of being superoxygenized, as well as barytes, by the superoxygenized acids. The hydrate of deutoxide of strontian resembles considerably that of barium: that of lime is in finer plates.

Probably by the same method I shall be able to oxygenize the earths, or, at least, some of them; and I shall be able to superoxydize a great many metallic oxides. To accomplish this, I propose to put an excess of base with the acid, or to dissolve the base in the acid, and then to precipitate it by potash; or I shall put the oxygenized muriates in contact with oxide of silver, which, seizing on the muriatic acid, will, in that way, favour the combination of the oxygen with the oxide which it is wished to superoxygenize.

ARTICLE II.

New Experiments on the Oxygenized Acids and Oxides. *

By M. L. I. Thenard. I ANNOUNCED in my preceding observations, that muriatic, nitric acids, &c. were susceptible of being oxygenated several times. It was of importance to be able to determine the quantity of oxygen which they were capable of taking up. This I have done with regard to muriatic acid, as I shall state briefly. I took liquid muriatic acid of such a degree of strength that when combined with barytes, a solution was produced, which, when slightly evaporated, deposited crystals of muriate of barytes. I saturated this acid with deutoxide of barium reduced into a soft paste by water and trituration. I then precipitated the barytes from the liquid by adding the requisite quantity of

• Translated from the Ann. de Chim. et Phys, ix, 51. (Sept. 1818.)

sulphuric acid. I then took the oxygenized muriatic acid and treated it with deutoxide of barium and sulphuric acid to oxygenize it anew.

In this way I charged it with oxygen as often as 15 times. This process is conducted the first five or six times without the evolution of oxygen gas; especially if the muriatic acid be not completely saturated, and if the muriate be poured into the sulphuric acid; but beyond that point it is difficult not to lose a little oxygen. However, the greatest part of this gas remains united to the acid. In this way I obtained an acid which contained 32 times its volume of oxygen at the temperature of 689 Fahr. and under a pressure of 29.922 inches of mercury; and only 4 times its volume of muriatic acid ; that is to say, that the volume of oxygen being seven, that of the muriatic acid was only one.*

Although the oxygenized muriatic acid, prepared in the way just described, contains a great quantity of oxygen, it is not yet saturated with it, being still capable of receiving a new portion. But to make it absorb the gas with facility, we must adopt a new method. This method consists in putting the oxygenized muriatic acid in contact with the sulphate of silver. There is immediately formed insoluble chloride of silver and oxygenized sulphuric acid, which is very soluble. When this last is separated by the filter, muriatic acid is added, but in smaller quantity than what existed in the oxygenized muriatic acid employed at first. A quantity of barytes, just' sufficient to precipitate the sulphuric acid, is then added. Instantly the oxygen leaving the sulphuric acid to unite with the muriatic acid brings that acid to the highest point of oxygenation. Thus we see that we can transfer the whole of the oxygen from one of these acids to the other; and on a little reflection, it will be evident that to obtain sulphuric acid in the highest degree of oxygenation, it will be merely necessary to pour barytes water into oxygenized sulphuric acid so as to precipitate only a part of the acid. All these operations, with a little practice, may be performed without the least difficulty:

By combining the two methods just described, I can obtain oxygenized muriatic acid containing nearly 16 times as many volumes of oxygen as of muriatic acid. It was so weak, that from one volume of acid I could only extract 3.63 volumes of oxygen gas under a pressure of 29.922 inches of mercury, and at the temperature of 65.3o.

Oxygenized muriatic acid exhibited several new phenomena to me, worthy of being related.

When recently prepared, it does not disengage any air bubbles when filtered; but soon after we perceive very small bubbles

Such an acid must be composed of 1 atom muriatic acid and 28 atoms oxygen !--T.

+ Such acid must be a compound of I atom muriatic acid and 64 atoms oxygen !--T.

make their appearance at the bottom of the vessel, ascend, and burst at the surface of the liquid. This even happens when the acid is only once oxygenized. Suspecting that this slow decomposition might proceed from the action of light, I filled almost completely a small flagon with acid, and after corking it, turned it upside down, and placed it in a dark place. After some hours, an explosion took place. The acid contained more than 30 times its volume ; yet when this same acid was put under the exhausted receiver of an air-pump, it allowed but a small quantity of the gas which it contained to be disengaged.

Hitherto I had imagined that the whole of the oxygen was disengaged from the muriatic acid at a temperature below ebullition, but this is not the case. After boiling oxygenized muriatic acid for half an hour, I still found oxygen in it.

It is by means of the oxide of silver that we can demonstrate the presence of oxygen in oxygenized muriatic acid which has been boiled. Scarcely does it come in contact with it but oxygen is suddenly disengaged. This oxide enables us to determine with facility, the quantity of oxygen contained in oxygenized muriatic acid. The analysis requires only a few minutes. Take a graduated glass tube, fill it almost entirely with mercury, pour into it a determinate volume of acid, fill the tube completely with mercury, and turn it upside down in the mercurial trough. Let up into the acid an excess of oxide of silver suspended in water. Immediately we see disengaged, and may read off on the tube, the quantity of oxygen contained in the acid. We can estimate the quantity of chlorine ; and, of consequence, the muriatic acid, by decomposing a part of the acid itself by means of nitrate of silver. *

The disengagement of oxygen from the oxygenized muriatic acid is so rapid, that it would be dangerous to operate upon a weak acid, which contained 26 or 30 volumes of oxygen." The tube would probably escape from the hands of the operator, or would break. Accordingly nothing can equal the effervescence which takes place when we plunge a tube containing oxide of silver and agitate it in some grammes of the acid of which we have just spoken. As that acid is immediately destroyed, the oxygen is restored to its liberty, and escapes with violence, driving the liquid before it.

When the most oxygenized muriatic acid is poured upon the sulphate, the nitrate, or the fluate of silver, no effervescence takes place. All the oxygen unites with the acid of the salt, while the muriatic acid forms with the oxide of silver water and a chloride.

I have already made several attempts to ascertain if the oxygenized acids be capable of taking up so much the more

* Having just observed that in this experiment there is a portion of the oxygen of the oxide of silver disengaged, it is obvious that we must take an account of this quantity to get an accurate result. See next paper.

[ocr errors]

oxygen the more real acid they contain ; or whether the water by its quantity has not an influence on the greater or smaller oxygenizement of the acid. My essays have not yet enabled me to answer that question.

I have attempted likewise, without any decisive success, to oxygenate magnesia and alumina ; but I have succeeded in superoxygenating several other oxides ; namely, oxide of zinc, oxide of copper, oxide of nickel. We should not succeed, or, at least, we should succeed very imperfectly, if we satisfied ourselves with adding oxygenized acid to the saline solutions of these three metals and precipitating the liquid by potash.

It is necessary to dissolve the oxides of these metals in oxygenized muriatic acid three or four times, and to decompose the oxygenized muriate by potash or soda, taking care to add but a small excess of these bodies. The preparation of superoxide of copper requires an additional precaution; namely, to put the deutoxide of copper into oxygenized muriatic acid in portions ; so that the acid shall always be in excess. If the oxide predominates, the greater part of the oxygen is disengaged. In all cases the oxide is precipitated in a gelatinous mass, or in the state of a hydrate. That of zinc is yellowish; that of copper olive-green; and that of nickel, dirty, dark apple-green. The first two allow a portion of their oxygen to be disengaged at the ordinary temperature. When they are boiled in water, the disengagement is still more abundant; but they do not give out (especially the superoxide of zinc) all the oxygen which they have absorbed; for when we dissolve them afterwards in muriatie acid, and heat the liquid, we obtain a new quantity of gas. The oxide of nickel is decomposed likewise at the boiling temperature, and its decomposition begins even below that point. When treated with muriatic acid, it is dissolved like the oxides of zinc and copper, and is disoxygenated by heat without the evolution of chlorine. We may add likewise that these different oxygenated hydrates recover the colours which characterize the ordinary oxides after they have been boiled in water. Thus the hydrate of zinc passes from yellow to white, that of copper from olive-green to dark brown. M. Rothoff, a Swedish chemist, had already observed that the deutoxide of nickel is decomposed by desiccation.

These new hydrates resemble, as we see, those of barytes, strontian, and líme, and form a class analogous to that of the oxygenized acids. I shall probably discover more of them.

ARTICLE III.

Fifth Series of Observations on the Oxygenized Acids and Oxides.*

By M. Thenard. (Read to the Academy of Sciences Oct. 5, 1818.)

The facts, of which this series of observations consist, are so remarkable that they will probably excite some surprize in the most distinguished chemists. I shall state them as concisely as possible.

1. Oxygenized nitric and muriatic acids dissolve the hydrate of the deutoxide of mercury without effervescence; but if we afterwards pour an excess of alkali into the solution, much oxygen is disengaged, and the oxide of mercury, which reappears at first with a yellow colour, is speedily reduced.

2. This hydrate is reduced equally when placed in contact with the oxygenized nitrate, or muriate of potash. We see it pass from yellow to grey, while, at the same time, much oxygen is disengaged.

3. Oxide of gold extracted from the muriate by means of barytes, and containing a little of that base which gave it a greenish tint, was put, while in a gelatinous state, into oxygenized muriatic acid. A strong effervescence immediately took place, owing to the disengagement of oxygen. The oxide became purple, and soon after was completely reduced.

4. Oxygenized sulphuric, nitric, and phosphoric acids make the oxide of gold become at first purple, as well as oxygenized muriatic acid, but the oxide, instead of assuming afterwards the aspect of gold precipitated by the sulphate of iron, becomes dark brown. These experiments seem to tend to show the existence of a purple oxide of gold.

5. When oxygenized nitric acid is poured upon oxide of silver, a strong effervescence takes place, owing entirely to the disengagement of oxygen, as in the preceding cases. One portion of the oxide of silver is dissolved, the other is reduced at first, and then dissolves likewise, provided the quantity of acid be sufficient. The solution being completed, if we add potash to it by little and little, a new effervescence takes place, and a dark violet precipitate falls ; at least, this is always the colour of the first deposite. This deposite is insoluble in ammonia, and, according to all appearance, is a protoxide of silver, similar tó what an English chemist has observed while examining the action of ammonia on oxide of silver.

6. Oxygenized sulphuric and phosphoric acids likewise partially reduce the oxide of silver, occasioning a strong efferPescence.

Translated from the Aon, de Chim. et Phys. ix. 91."

« PrécédentContinuer »