On some salts and products of decomposition of pyromeconic acid / by James F. Brown.

Date:
[1852?]
Catalogue details

Licence: Public Domain Mark

Credit: On some salts and products of decomposition of pyromeconic acid / by James F. Brown. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    which it crystallizes in four-sided prisms of considerable size. It IS slightly acid to litmus, and even after three crystallizations from boihng water it retained its acidity. It is completely volatile at 212°. A quantity having been exposed to that temperature for about fourteen hours, was found to have entirely disappeared. This property may serve as a test of its purity from paracomenic acid, with which pyromeconic, as fu-st sublimed, is always conta- minated, that acid requiring a much higher heat to volatihze it. It gives, as is well known, a deep red colour ^dth persalts of iron, and does not precipitate chloride of calcium, barium, manganese^ nor sulphate of magnesia, either hot or cold, even on the addition of a small quantity of ammonia. Bichloride of mercury gives after some time a white amorphous precipitate, soluble on boiling the fluid. When a hot aqueous solution of pyromeconic acid is treated with strong caustic potash in excess, and allowed to stand some hours, crystals soon begin to form, which upon examina- tion proved to be the acid unaltered; a similar experiment was made with ammonia, but with the same result, the fluids in both cases becoming neai-ly black. To ascertain the purity of the acid, the following analysis was made of it, dried in vacuo, after one sublimation. 5-74 grains substance gave 11*133 carbonic acid and 1*905 water. Calculation. Experiment. f Carbon . . 53-23 53-57 60 Hydrogen . 3*71 3-57 4 Oxygen . . 43-06 42-86 0^ 48 100-00 100-00 112 The formula of the acid is therefore represented by C10H3O5 + HO. Pyromeconate of Baryta.—This salt may be obtained by mixing a warm ammoniacal solution of pyromeconic acid with acetate of baryta, when it makes its appearance after a short time in small colourless silky needles. In dilute solutions they do not appear immediately, but after standing some time they com- mence forming and rapidly increase. It is the most soluble in water of all the earthy salts of this acid,—181-90 grains of a saturated solution at 60° F. gave on evaporation at 212° a residue of 4-50 grains = 2-50 per cent. It is of sparing solubility in alcohol. Like the other pyromeconates, it reacts strongly alka- line, and gives a slight red colour with chloride of iron, which may be made much more apparent if the crystals be employed instead of a solution of the salt. By evaporation in vacuo it deposits itself in short prisms of a yellowish colour. When ex-