Table of the Combinations of Boracic Acid, with the Salifiable Bases, in the Order of Affinity.
| Bases. | Neutral Salts. | ||
| Lime | Borat of | lime. | |
| Barytes | barytes. | ||
| Magnesia | magnesia. | ||
| Potash | potash. | ||
| Soda | soda. | ||
| Ammoniac | ammoniac. | ||
| Oxyd of | |||
| zinc | zinc. | ||
| iron | iron. | ||
| lead | lead. | ||
| tin | tin. | ||
| cobalt | cobalt. | ||
| copper | copper. | ||
| nickel | nickel. | ||
| mercury | mercury. | ||
| Argill | argill. | ||
Note.—Most of these combinations were neither known nor named by the old chemists. The boracic acid was formerly called sedative salt, and its compounds borax, with base of fixed vegetable alkali, &c.—A.
Sect. XXII.—Observations upon Boracic Add and its Combinations.
This is a concrete acid, extracted from a salt procured from India called borax or tincall. Although borax has been very long employed in the arts, we have as yet very imperfect knowledge of its origin, and of the methods by which it is extracted and purified; there is reason to believe it to be a native salt, found in the earth in certain parts of the east, and in the water of some lakes. The whole trade of borax is in the hands of the Dutch, who have been exclusively possessed of the art of purifying it till very lately, that Messrs L'Eguillier of Paris have rivalled them in the manufacture; but the process still remains a secret to the world.
By chemical analysis we learn that borax is a neutral salt with excess of base, consisting of soda, partly saturated with a peculiar acid long called Homberg's sedative salt, now the boracic acid. This acid is found in an uncombined state in the waters of certain lakes. That of Cherchiais in Italy contains 94-1/2 grains in each pint of water.
To obtain boracic acid, dissolve some borax in boiling water, filtrate the solution, and add sulphuric acid, or any other having greater affinity to soda than the boracic acid; this latter acid is separated, and is procured in a crystalline form by cooling. This acid was long considered as being formed during the process by which it is obtained, and was consequently supposed to differ according to the nature of the acid employed in separating it from the soda; but it is now universally acknowledged that it is identically the same acid, in whatever way procured, provided it be properly purified from mixture of other acids, by warning, and by repeated solution and cristallization. It is soluble both in water and alkohol, and has the property of communicating a green colour to the flame of that spirit. This circumstance led to a suspicion of its containing copper, which is not confirmed by any decisive experiment. On the contrary, if it contain any of that metal, it must only be considered as an accidental mixture. It combines with the salifiable bases in the humid way; and though, in this manner, it is incapable of dissolving any of the metals directly, this combination is readily affected by compound affinity.
The Table presents its combinations in the order of affinity in the humid way; but there is a considerable change in the order when we operate via sicca; for, in that case, argill, though the last in our list, must be placed immediately after soda.
The boracic radical is hitherto unknown; no experiments having as yet been able to decompose the acid; We conclude, from analogy with the other acids, that oxygen exists in its composition as the acidifying principle.