Sect. XXXIX.—Observations upon Lactic Acid, and its Combinations with Salifiable Bases[51].
The only accurate knowledge we have of this acid is from the works of Mr Scheele. It is contained in whey, united to a small quantity of earth, and is obtained as follows: Reduce whey to one eighth part of its bulk by evaporation, and filtrate, to separate all its cheesy matter; then add as much lime as is necessary to combine with the acid; the lime is afterwards disengaged by the addition of oxalic acid, which combines with it into an insoluble neutral salt. When the oxalat of lime has been separated by decantation, evaporate the remaining liquor to the consistence of honey; the lactic acid is dissolved by alkohol, which does not unite with the sugar of milk and other foreign matters; these are separated by filtration from the alkohol and acid; and the alkohol being evaporated, or distilled off, leaves the lactic acid behind.
This acid unites with all the salifiable bases forming salts which do not cristallize; and it seems considerably to resemble the acetous acid.
Table of the Combinations of Saccholactic Acid with the Salifiable Bases, in the Order of Affinity.
| Bases. | Neutral Salts. | ||
| Lime | Saccholat of | lime. | |
| Barytes | barytes. | ||
| Magnesia | magnesia. | ||
| Potash | potash. | ||
| Soda | soda. | ||
| Ammoniac | ammoniac. | ||
| Argill | argill. | ||
| Oxyd | of zinc | zinc. | |
| manganese | manganese. | ||
| iron | iron. | ||
| lead | lead. | ||
| tin | tin. | ||
| cobalt | cobalt. | ||
| copper | copper. | ||
| nickel | nickel. | ||
| arsenic | arsenic. | ||
| bismuth | bismuth. | ||
| mercury | mercury. | ||
| antimony | antimony. | ||
| silver | silver. | ||
Note.—All these were unknown to the ancient chemists.—A.
Sect. XL.—Observations upon Saccholactic Acid, and its Combinations.
A species of sugar may be extracted, by evaporation, from whey, which has long been known in pharmacy, and which has a considerable resemblance to that procured from sugar canes. This saccharine matter, like ordinary sugar, may be oxygenated by means of nitric acid: For this purpose, several portions of nitric acid are distilled from it; the remaining liquid is evaporated, and set to cristallize, by which means cristals of oxalic acid are procured; at the same time a very fine white powder precipitates, which is the saccholactic acid discovered by Scheele. It is susceptible of combining with the alkalies, ammoniac, the earths, and even with the metals: Its action upon the latter is hitherto but little known, except that, with them, it forms difficultly soluble salts. The order of affinity in the table is taken from Bergman.
Table of the Combinations of Formic Acid, with the Salifiable Bases, in the Order of Affinity.
| Bases. | Neutral Salts. | ||
| Barytes | Formiat of | barytes. | |
| Potash | potash. | ||
| Soda | soda. | ||
| Lime | lime. | ||
| Magnesia | magnesia. | ||
| Ammoniac | ammoniac. | ||
| Oxyd of | |||
| zinc | zinc. | ||
| manganese | manganese. | ||
| iron | iron. | ||
| lead | lead. | ||
| tin | tin. | ||
| cobalt | cobalt. | ||
| copper | copper. | ||
| nickel | nickel. | ||
| bismuth | bismuth. | ||
| silver | silver. | ||
| Argill | argill. | ||