CHLORIDE OF BARIUM.

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Composition. —The following is the composition of this salt:—

Eq. Eq.Wt. Per Cent. Berzelius . Berard.

Baryta. 1 77 77*7 77*9 78

Carbonic Acid . . 1 . 22 22*2 221.22

Carbonate Baryta .1 . 99 99'9.100 - 0.100

Purity. —It should he white, odourless, and tasteless. Neither causticammonia nor hydrosulphuric acid should produce any precipitate orchange of colour in the hydrochloric solution, hy which the absenceof alumina and metallic matter may be inferred. If excess of sulphuricacid be added to this solution, no precipitate should be occasioned bythe subsequent addition of carbonate of soda, by which the absence oflime is shown.

Physiological Effects, (a.) On vegetables. —Gemination does nottake place in carbonate of baryta. (Vogel, in Decand. Phys. Veget.p. 1341.)

( b.) On animals. —Cows and fowls have been destroyed by swallowingthe native carbonate. (Parkes, Chem. Essays, vol. i. p. 330.) Orfila{Toxicol. Gen.) says a drachm of the powder killed a dog in six hours ;but C. G. Gmelin ( Versuche uber d. Wirk. des Baryts, &c. p. 8) gave twodrachms to a dog: vomiting took place, and the animal was well thenext day. A drachm killed a rabbit in three hours. When applied to awound it has proved fatal. (Campbell, quoted by Christison , Treatise onPoisons, 3d ed. p. 532.) From the above experiments carbonate ofbaryta appears to act as an acro-narcotic poison: when swallowed itcauses vomiting, inflames the alimentary tube, becomes absorbed, andacts specifically on the nervous system, causing convulsions, paralysis,and insensibility.

(c.) On man. —Only one case illustrating its action on the human sub-ject has been published. (Dr. Wilson, Med. Gaz. vol. xiv. p. 487.) Ayoung woman swallowed half a tea-cupful of the powdered carbonate:in two hours she had dimness of sight, double vision, ringing in the ears,pain in the head, and throbbing in the temples, a sensation of distensionand weight at the epigastrium, distension of stomach, and palpitation.Subsequently she had pains in the legs and keees, and cramps in thecalves. A day or two after the cramps became more severe. Thesesymptoms slightly modified continued for a long time.

Uses. —Carbonate of baryta is employed in the preparation of thechloride of barium. It is not administered as a medicine.

Antidote. —-(Vide Barii Chloridum.)

Ba'rii Chlo’ridum.- — Chlo'ride of Ba'rium.

History. —This compound was discovered by Scheele in 1775. Itwas at first termed terra ponderosa salita, and afterwards muriate ofbarytes.

Preparation. 1 . From the native carbonate of baryta. —The followingare the directions given in the London Pharmacopoeia :—Add ten ouncesof carbonate of baryta, broken in small pieces, to half a pint of hydro-chloric acid mixed with two pints of distilled water. Apply heat, and