remarkable acid is a compound of fluoric and boracic acids. Thenard and Guy Lussac, the discoverers of it, have given it the name of fluo-boric acid.

When fluor spar and sulphuric acid are heated in leaden vessels, no gas whatever is obtained, but only an acid liquid, consisting of fluoric acid and water. When this liquid is exposed to the air, it emits vapours. When mixed with water, it becomes hot, and even enters into ebullition. When brought in contact with glass, it acts upon it, becomes hot, and is converted into siliciferous fluoric acid gas. When allowed to touch the skin, a white spot is formed with the pain of a burn, which terminates in a blister. When brought in contact with potassium, a violent combustion takes place; hydrogen gas is evolved, and fluate of potash and water disengaged. When potassium is placed in contact with siliciferous fluoric acid gas, a white crust gradually covers its surface. When heat is applied, the metal bursts through the crust, gradual ly changes its colour, and at last breaks out into a most splendid combustion. The fluoric acid gas disappears, and a chocolate-coloured mass remains, partly at the bottom of the retort and partly sublimes. Some hydrogen gas is evolved, but the proportion of it diminishes according to the care with which the fluoric acid gas has been dried. The chocolatecoloured mass, when viewed under the microscope, appears a heterogeneous mixture of three different substances. It effervesces in water, and burns when heated in the open air, and is converted into a white saline mass. There can be little doubt that in this experiment the fluoric acid is decomposed; but its basis remaining com

bined with the potash formed, an being likewise mixed with siliceou matter, it has not been possible to a certain its nature. Mr Dalton indee draws a different consequence fro the experiment. He thinks that th hydrogen gas evolved constitutes th basis of the fluoric acid gas, and henc considers it as a compound of oxyge and hydrogen: but the experime does not seem to warrant any suc conclusion.

11. Muriatic acid is one of the ch mical substances which has been t longest known and in the most com mon use ever since men began to mai experiments on metallic bodies. Ma attempts have been made to decor pose it, but it resisted all the effor of the most indefatigable chemist and baffled all their skill. The di covery of potassium induced Mr Da to apply the action of that power! separator of oxygen, in order if p sible to detect its base. The expe ment was unsatisfactory. Thena and Guy Lussac made the same periment with a similar result. T failure was ascribed to the presen of water in the acid gas. A set experiments was made by these g tlemen, in order to deprive the ga water, and to prepare it quite from water. The conclusion wh they drew from these experime was, that the compounds contain the acid cannot be decomposed less water be present, because m tic acid gas cannot exist in a separ state, unless it be united with a tain portion of water. Water th it followed, was an essential con tuent of muriatic acid This 1 gas. a very singular conclusion. We acquainted with about 23 gase bodies. Now water does not app to be essential to the gaseous stat

y of them except muriatic acid; hy then should it be essential to e constitution of that gaseous body? There is a very remarkable gaseis body first discovered by Scheele, d called by him dephlogisticated uriatic acid; afterwards examined ith much care by Berthollet, and lled by him oxymuriatic acid, beuse he considered it as a compound muriatic acid and oxygen. In is conclusion all scientific chemists greed with him; and it was the rrent opinion that the oxygen in is substance was but loosely comned. Hence the reason of the very werful manner in which it acts on mbustibles, setting them on fire, many cases, by simple contact. enard and Guy Lussac were induto examine this gaseous body w, on the supposition that it would easy to deprive it of its oxygen, 1 thus to obtain muriatic acid in a te of purity, and proper for atpting its decomposition. But ir efforts were not crowned with cess. The results, however, which y obtained, were exceedingly cuus and unexpected. They found t no substance, not even charcoal, apable of depriving oxymuriatic of oxygen, and reducing it to the e of muriatic acid, unless it conis water, or at least hydrogen, ich, in their opinion, combined h the oxygen of the acid, and Hence the muriatic

ned water.

, whenever it was obtained, was ays in its usual state, and of course taminated with water. Their exments led to the conclusion, that muriatic acid, instead of being a e compound, is one of the most nate combinations in nature, and wo constituents cannot be sepad directly by any agent in our er. No degree of heat alters its

nature, and it never assumes the state of muriatic acid, unless water or hydrogen be present.

These unexpected results induced Mr Davy to turn his attention to the subject, and to endeavour to deprive this gaseous body of oxygen. But all his endeavours were equally unsuccessful. Well-burnt charcoal

may be kept by means of the galvanic battery, in a white heat in this gas, when well dried, without producing the smallest alteration on it. When phosphorus is burnt in it a solid matter is obtained, which shews no indication of containing phosphorus, or phosphoric acid, and which, when placed in contact with ammoniacal gas, absorbs it, and is converted into a white, tasteless, insoluble substance, having a strong resemblance to silica in its properties. When tin or any metal is burnt in this gas, no indication appears of the formation of an oxide. In short, no oxide or acid can be separated from any of the products formed by means of this gas, unless we employ water in the first place to separate the excess of acid. When equal bulks of oxymuriatic acid gas and hydrogen gas are mixed together in a close vessel, no change takes place in the dark, but if they be exposed to the light they gradually disappear, and muriatic acid gas is found in their place. If this mixture be exposed to the sun's rays, as was first observed by Mr Dalton, and by Thenard and Guy Lussac, it takes fire, and explodes; if the light be not strong, it merely disappears rapidly, and assumes the form of muriatic acid gas, which, if the experiment be made over water, is instantly absorbed. The diminution of bulk which takes place when this experiment is properly made, does not exceed th of the

The mean of which is Sp. gr. of muriatic acid

1.272

. 1.278

From this last fact, compared with the impossibility of decomposing oxymuriatic acid, Mr Davy has drawn as a conclusion, that it is not a compound, as has hitherto been supposed, but a simple substance, and that muriatic acid is a compound of oxymuriatic acid and hydrogen united in equal bulks. This conclusion is remarkably supported by the comparison of the specific gravities of these different gases, and by the small change of bulks which takes place when a mixture of oxymuriatic and hydrogen gases is changed into mu

riatic acid.

This opinion of Mr Davy is very nearly the same with the theory of Mr Scheele, the original discoverer of the oxymuriatic acid. Mr Davy has supported it with much ingenuity and sagacity, and by a great number of new and curious experiments, in two dissertations, which reach beyond the period of our history, and upon which, therefore, we cannot enter at present. The subject cannot be considered as completely decided; but, in our opinion, the weight of evidence is on the side of Mr Davy's theory. The most formidable objection, an objection which Mr Davy has not yet removed in a satisfactory manner, is the great quantity of oxygen obtain

ed when hyperoxymuriatic of potash is heated. Now this salt is formed by causing a current of oxymuriatic acid to pass through a solution of potash in water.

It is obvious, that if Mr Davy's theory prove correct, the term oxy muriatic acid applied to this simple substance is improper. Mr Dary has proposed to distinguish it by the name chlorine, derived from the green colour which it has when in the gase ous state.

If the nature of this substance, a suggested by Mr Davy, prove acc rate, a very great alteration must be made in the presently received theory of chemistry. There will now be two simple supporters of combus tion, namely, oxygen and chlorine, and two distinct sets of compounds formed by the union of each with combustible bodies. Muriatic acid is a compound of chlorine and by drogen. It combines likewise with sulphur and with phosphorus, and forms bodies which are decomposed when placed in contact with water, and resolved into muriatic acid and sulphuric and phosphoric acids. With charcoal it does not combine. With the metals it unites, and forms those compounds denominated butters by the old chemists, and improperly call ed muriates by modern writers. Th what is called muriate of silver is compound of chlorine and silver, fuming liquor of libavius, a con pound of chlorine and tin; and com mon salt, a compound of chlorine and sodium. Mr Davy proposes tinguish these compounds by the names of the basis and the termin tions ine or ane. Thus muriate of silver he calls argentane, muriate l barytes, barytane, &c.

to div

12. Having detailed at sufficie length the important discoveries of

Mr Davy, we must now turn our attention to Mr Dalton, one of the most ingenious and industrious philosophers of the present day. By the introduction of a very simple but most important theory, he has contributed very essentially to the improvement of chemical analysis, and to the accuracy of our notions respecting the constitution of compound bodies. According to him, when substances combine together, they unite either to each other atom to atom, or one atom of the one combines with a determinate number of atoms of the other. Water, for example, is composed by the union of one atom of oxygen with one atom of hydrogen. Now water is a compound of about 87.5 parts by weight of oxygen, and 12.5 of hydrogen, or of 7 parts of oxygen, and 1 of hydrogen. Hence we know that the relative weights of an atom of each of these bodies are to each other as 7 to 1. Therefore, if we denote the weight of an atom of hydrogen by 1,

we must denote that of an atom of oxygen by 7. In like manner, ammonia is composed of an atom of hydrogen, combined with an atom of azote. Now it consists of 81.5 parts by weight of azote, 18.5 parts of hydrogen, or nearly of 4.5 azote, and I hydrogen. Hence, if the weight of an atom of hydrogen be represented by 1, that of an atom of azote will be 4.5. In like manner, from the analysis of carbonic acid, an atom of charcoal will be found to weigh about 5, an atom of sulphur weighs about 13, and an atom of phosphorus about 9.

Now, knowing the relative weights of the different atoms, and the number of atoms which combine, it is easy to determine the composition of any compound, and likewise the relative weight of a particle of it. The following table exhibits a few examples of these determinations, to render them more familiar to the reader:

Ammonia

Carbonic acid : Olefiant gas

1 hydrogen. 1 carbon.

1 hydrogen. 2 hydrogen.

1 azote

2 oxygen

1 carbon

Carbureted hydrogen

1 carbon

Nitric acid

Nitrous gas

Nitrous oxide

1 oxygen

Sulphuric acid

3 oxygen

Sulphurous acid

2 oxygen

2 oxygen

2 E

Phosphoric acid Phosphorous acid Nitrous acid

VOL. II. PART II.

1 oxygen 1 nitric acid

2 azote.
1 sulphur.

1 sulphur.
1 phosphorus.
1 phosphorus.
1 nitrous gas.