Prop., &c. A crystalline white powder; it is soluble in 10 parts of water at 60° Fahr., but it cannot be dissolved in even warm water without partial decomposition; it is more pleasant tasted and more feebly alkaline than the carbonate of the same base. When absolutely pure it does not darken turmeric paper, or only very slightly. The dose is from 10 to
40 gr., as an antacid and absorbent. It is much employed in the preparation of effervescing powders and draughts, for which purpose
20 gr. of commercial bicarbonate of sodium
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are taken with
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18 gr. of crystallised tartaric acid;
17 gr. of crystallised citric acid; or
1⁄2 fl. oz. of lemon juice.
The quantity of bicarbonate any given sample contains may be approximately determined by well washing 100 gr. of the salt with an equal weight of water, and filtering the solution. The residuum left upon the filter, dried at a heat of 120° Fahr., and weighed, gives the per-centage of pure bicarbonate of sodium present (very nearly). The solution of this in water will give only a very trifling white precipitate with corrosive sublimate; whilst the filtered portion, which was used to wash the salt, will give a red one, if it contains the simple carbonate of sodium.
Sodium, Chloride of. NaCl. Syn. Sodii chloridum (B. P., Ph. L., & D.), Sodæ murias (Ph. E.), L. This important and wholesome compound appears to have been known in the earliest ages of which we have any record. It is mentioned by Moses (Gen. xix, 26), and by Homer in the Iliad (lib. ix, 214). In ancient Rome it was subjected to a duty (vectigal salinarium); and even at the present day a similar tax furnishes no inconsiderable portion of the revenue of certain nations. Common salt forms no small portion of the mineral wealth of England, and has become an important article of commerce in every part of the known world. The principal portion of the salt consumed in this country is procured by the evaporation of the water of brine springs. It is also prepared by the evaporation of sea-water (hence the term ‘sea-salt’), but this process has been almost abandoned in England, being more suited to hot dry climates or to very cold ones.
Var. Bay salt; SAL MARINUS, SAL NIGER; imported from France, Portugal, and Spain, and obtained from sea-water evaporated in shallow ponds by the sun; large-grained and dark-coloured.—British bay salt, Cheshire large-grained s.; by evaporating native brine at a heat of 130° to 140° Fahr.; hard cubical crystals. Both of the above are used to salt provisions for hot climates, as they dissolve very slowly in the brine as it grows weaker. Cheshire stoved salt, LUMP S., BASKET S.; obtained by evaporating the brine of salt springs; small flaky crystals.—London’s patent solid salt; Cheshire rock salt, melted and ladled into moulds.—Rock salt, FOSSIL S.; SAL GEMMÆ, SAL FOSSILIS; found in mineral beds in Cheshire; has commonly a reddish colour; chiefly exported for purification.
Prop. Pure chloride of sodium is fixed in
the air; crystallises in anhydrous cubes, which are often grouped into pyramids or steps; dissolves in about 21⁄2 parts of water at 60° Fahr.; its solubility is not increased by heat; it is slightly soluble in proof spirit; insoluble in alcohol; decrepitates when heated; fuses at a red heat, and volatilises at a much higher temperature.
Pur., &c. The common salt of commerce contains small portions of chloride of magnesium, chloride of calcium, and sulphate of calcium; and hence has commonly a slightly bitter taste, and deliquesces in the air. To separate these, dissolve the salt in 4 times its weight of pure water, and drop into the filtered solution, first, chloride of barium, and then carbonate of sodium, as long as any precipitate falls; filter, and evaporate the clear fluid very slowly, until the last crystallises, which is pure chloride of sodium. (‘Thomson’s Chem.,’ ii, 377.) For medical purposes the Ph. E. orders the salt to be dissolved in boiling water, and the solution to be filtered and evaporated over the fire, skimming off the crystals as they form, which must then be quickly washed in cold water, and dried. A solution of pure salt is not precipitated by a solution of carbonate of ammonium, followed by a solution of phosphate of sodium; a solution of 9 gr. in distilled water is not entirely precipitated by a solution of 26 gr. of nitrate of silver. (Ph. E.)
Uses. Common salt is stimulant, antiseptic, and vermifuge, and is hence employed as a condiment, and for preserving animal and vegetable substances. It is also occasionally used in medicine, in clysters and lotions.