308
ELEMENTS OE MATERIA MEDICA.
readily distinguished from the hitartrate by its deliquescent property, its jgreater solubility, and its want of acidity. j
Composition. —The following is the composition of this salt:—
Eq. Eq.Wt. Per Cent. Berzelius .
Potash. 1 . . . . 48 ... . 42-1 .... 41*31
Tartrate of Potash 1 .... 114 ... . 100*0 .... 100*00
Impurity. —It may contain excess of acid or base, either of which iseasily recognised ; the one by litmus, the other by turmeric. The sul-phates may be detected by chloride of barium throwing down a whiteprecipitate insoluble in nitric acid.
Physiological Effects. —This salt is a gentle purgative, analogous inits action to the sulphate of potash, from which it differs in being milderin its operation, and partially digestible ; for, like the other vegetable saltsof the alkalies, it is decomposed in the system, and converted into thecarbonate, in which state it is found in the urine.
It is said to have the power of preventing the griping of other moreactive cathartics ; as senna and scammony ; but, from my own personalobservations, I doubt the correctness of this statement.
Uses. —It is employed as a mild purgative in dyspepsia, at the com-mencement of diarrhoea, in some liver complaints, &c. Sometimes it is ,used as an adjunct to other more active purgatives: as the infusion ofsenna. (
Administration. —It may be given in doses of from two to three ]drachms to half an ounce, or even an ounce. j
Order 11.—Compounds of Sodium.
So'dii Chlo'ridum.—Chid ride of So'dium.
History. —As this salt is a necessary and indispensable seasoning toour food, it doubtless must have been known to, and employed by, the jfirst individuals of our race. The earliest notice of it occurs in thewritings of Moses, (Gen. xix. 26; Lev. ii. 13) and Homer (Iliad, lib . ix. ^214). It has received various names, such as common salt, culinary salt, |and muriate or hydrochlorate of soda. ’
Natural History . —It occurs in both kingdoms of nature.
(a.) In the inorganized kingdom. —An enormous quantity of this salt iscontained in the waters of the ocean. At an average calculation seawater contains 2'5 per cent, of chloride of sodium (vide various analysesof this fluid in Thomson’s System of Chemistry, 6th ed. vol. iii. p. 196).
It is found also in great abundance in mineral w aters (Gairdner, OnMineral Springs, p. 12). It has not hitherto been found in the oldest ;stratified rocks (De la Beche, Researches in Theoret. Geol . p. 31), but is 'met with in all the later formations. Thus Mr. Featherstonhaugh (Phil. .Mag. N. S. vol. v. p. 139 ; vol. vi. p. 75 ; and vol. vii. p. 198) states that 1salt or brine springs occur in certain parts of the United States , in the jold transition slate rocks. Salt springs occur in various parts of England,in the coal measures (Bakew r ell, Introd. to Geology, 4th ed. p. 252). The jrock salt of Cheshire, and the brine springs of Worcestershire , occur in ;