This section is from the book "An Experimental History Of The Materia Medica", by William Lewis.
(a) This acid appears to proceed, not from the pure marine salt, but from the calcareous muriatic slt, or a combination of marine acid with earth, which all the common sorts of sea salt are found to partake of. On dropping into a solution of common sea salt a little alkaline lye, the earth precipitates; and the acid, being thus saturated with alkali, is no longer disposed to evaporate on boiling down the liquor.
The acid of sea salt is completely disengaged from its alkaline basis by the more powerful acid of vitriol; and may now be collected, in a concentrated state, by distillation; but as, in this concentrated state, its fumes very difficultly condense, a little water is commonly added to promote that effect. On ten pounds of dry sea salt, the college of London directs six pounds of oil of vitriol diluted with five pints of water, that of Edinburgh one pound of oil of vitriol diluted with equal its quantity of warm water, to be poured by little and little, under a chimney, that the operator may not be incommoded by the noxious fumes: the retort is placed in sand, and the distillation performed with a fire gradually increased till nothing more will arise. The spirit may be freed from its superfluons water, by a second distillation in a glass cucurbit; the phlegmatic part rising in a proper degree of heat, while the stronger acid remains behind. The distilled spirit proves nearly the same, whether the larger or smaller of the above proportions of oil of vitriol are used, the difference affecting chiefly the resi-duum: see the foregoing article. Its specific weight to that of water is stated by the London college at 1170 to 1000.
*(a) This assertion is contradicted by the success of some late attempts to supply ships with fresh water by the distillation of sea water. In these, good sweet water was obtained merely by fitting an apparatus to the ships' boilers in which salt water was used for common purposes. See, particularly, Pbipp's Voyage towards the North Pole,
Acidam mu-riaticum Ph. Lond,
Acidum muriatic um vul-go fpir. fal. marin. Ph, Ed.
The marine acid is distinguished from the. others, by its rising in white fumes; by its peculiar pungent smell; by its enabling the nitrous acid to dissolve gold, preventing its dissolving silver, and precipitating silver previ-ously dissolved, but producing no precipitation in solutions of calcareous earths. It is some-times given, from ten to sixty or seventy drops, properly diluted, as an antiphlogistic, diuretic, and for promoting appetite, and applied exter-nally to chilblains, which are said by Linnaeus to be radically cured by it in a short time, without fear of a return; but its principal use is in combination with other bodies.
Combined with volatile alkalies, it produces the officinal sal ammoniac. With the mineral fixt alkali, it regenerates common salt. With vegetable fixt alkalies, it forms a neutral salt of a sharper taste, and somewhat more difficult of fusion and solution, than common salt: this combination is prepared in the shops, by dropping into the marine spirit a lixivium of the fixt alkali till all effervescence ceases, and then evaporating the mixture to dryness: the same salt may be obtained from the matter which remains after the distillation of spirit of sal ammoniac with fixt alkali.
With calcareous earths, it forms a very pungent saline compound, which difficultly assumes a crystalline form, deliquiates in the air, dissolves not only in water but in rectified spirit of wine, and changes the colour of blue flowers of vegetables to a green. This salt is contained, in considerable quantity, in sea water, and remains fluid after the crystallization of its other saline matters: it is found also in fundry common waters, to which, like the calcareous nitre, it communicates, according to its quantity, a greater or less degree of hardness and indisposi-tion to putrefy: it is far more antiseptic than the perfect marine salt. It is said to be diuretic and lithontriptic: the medicine commonly fold as a lithontriptic under the name of liquid-shell, appears to be no other than a combination of this kind, confiding of calcined shells dissolved in marine acid. These combinations have been chiefly prepared, by mixing the calcareous earth with sal ammoniac, and urging the mixture with a gradual fire, till the volatile alkali of the sal ammoniac is either dissipated in the air or collected by distillation, and only its acid left incorporated with the earth: so much of the earth, as is satiated with the acid, may be sepa-rated from the reft by elixation with water.
Sal marin. fegeneratus vulgo.
Sal ammon. fixum vulgo. Sal muriatic, calcareus.
This acid dissolves, among metallic bodies, zinc and iron pretty readily; copper and tin languidly; bismuth and arsenic very difficultly and sparingly; lead, mercury, regulus of antimony, and silver, not at all, unless highly concentrated and applied in the form of fume: it dissolves, by digestion, all metallic bodies when reduced to a state of calx, gold not excepted. Though it difficultly unites with metals, it adheres to most .of them more strongly than any other acid, and in part volatilizes them: it renders them likewise more fusible in the fire than the other acids do, and more disposed to solution in spirit of wine.
Of itself it is nevertheless the most averse of all acids to a perfect union with vinous spirits. If poured gradually into thrice its quantity of rectified spirit of wine, and the mixture, after diges-tion for some days, submitted to distillation in a sand heat; the spirit that comes oyer, appears to be little other than the acid simply diluted with the vinous spirit; whereas, when the nitrous or vitriolic acids are treated in the same manner, a new compound is formed by the intimate coalition of the acid spirit with the inflammable (a). The dulcified marine acid has by some been held in great esteem against weakness of the stomach, indigestion, and other like complaints brought on by irregularities.