To obtain the sebacic acid, let some suet be melted in a skillet over the fire, alongst with some quick-lime in fine powder, and constantly stirred, raising the fire towards the end of the operation, and taking care to avoid the vapours, which are very offensive. By this process the sebacic acid unites with the lime into a sebat of lime, which is difficultly soluble in water; it is, however, separated from the fatty matters with which it is mixed by solution in a large quantity of boiling water. From this the neutral salt is separated by evaporation; and, to render it pure, is calcined, redissolved, and again cristallized. After this we pour on a proper quantity of sulphuric acid, and the sebacic acid passes over by distillation.
Sect. XLIV.—Observations upon the Lithic Acid, and its Combinations with the Salifiable Bases[53].
From the later experiments of Bergman and Scheele, the urinary calculus appears to be a species of salt with an earthy basis; it is slightly acidulous, and requires a large quantity of water for solution, three grains being scarcely soluble in a thousand grains of boiling water, and the greater part again cristallizes when cold. To this concrete acid, which Mr de Morveau calls Lithiasic Acid, we give the name of Lithic Acid, the nature and properties of which are hitherto very little known. There is some appearance that it is an acidulous neutral salt, or acid combined in excess with a salifiable base; and I have reason to believe that it really is an acidulous phosphat of lime; if so, it must be excluded from the class of peculiar acids.
Table of the Combinations of the Prussic Acid with the Salifiable Bases, in the order of affinity.
| Bases. | Neutral Salts. | ||
| Potash | Prussiat of | potash. | |
| Soda | soda. | ||
| Ammoniac | ammoniac. | ||
| Lime | lime. | ||
| Barytes | barytes. | ||
| Magnesia | magnesia. | ||
| Oxyd | of zinc | zinc. | |
| iron | iron. | ||
| manganese | manganese. | ||
| cobalt | cobalt. | ||
| nickel | nickel. | ||
| lead | lead. | ||
| tin | tin. | ||
| copper | copper. | ||
| bismuth | bismuth. | ||
| antimony | antimony. | ||
| arsenic | arsenic. | ||
| silver | silver. | ||
| mercury | mercury. | ||
| gold | gold. | ||
| platina | platina. | ||
Note.—-All these were unknown to former chemists.—A.
Observations upon the Prussic Acid, and its Combinations.
As the experiments which have been made hitherto upon this acid seem still to leave a considerable degree of uncertainty with regard to its nature, I shall not enlarge upon its properties, and the means of procuring it pure and dissengaged from combination. It combines with iron, to which it communicates a blue colour, and is equally susceptible of entering into combination with most of the other metals, which are precipitated from it by the alkalies, ammoniac, and lime, in consequence of greater affinity. The Prussic radical, from the experiments of Scheele, and especially from those of Mr Berthollet, seems composed of charcoal and azote; hence it is an acid with a double base. The phosphorus which has been found combined with it appears, from the experiments of Mr Hassenfratz, to be only accidental.