340
ELEMENTS OF MATERIA MEDICA.
when the effervescence has finished, strain and boil down, that crystalsmay be formed.
In this process one equivalent or 37 parts of hydrochloric acid reacton one equivalent or 99 parts of carbonate of baryta: the products areone equivalent or 22 parts of carbonic acid, which escape ; one equivalentor 9 parts of water, and one equivalent or 105 parts of chloride ofbarium.
REAGENTS. RESULTS.
fl eq. Carb. Acid.22-1 eq. Carb . Acid .... 22
) i eq Barvta 77 S 1 e Q- OW 8 - -1 eq. Water . 9
(ieq. rar>™''<i e q. Bar»>. 69 x———
1 eq. HydrocbK. (1 eq. Hydrogen. , 1 —-
Acid37. (1 eq. Chlorine. 36--- 1 eq. Chloride Barm. ]05
2. From the native sulphate of baryta. —As a sulphate of baryta can beobtained in greater abundance and cheaper than the carbonate, manufac-turers usually prepare the chloride, as well as other salts, of barium fromit. There are several modes of proceeding, hut the most common one isthe following :—Make finely powdered sulphate into a paste with aboutan equal volume (or a sixth part of its weight) of flour (or charcoal); andexpose it in a covered crucible to an intense heat for two hours. The carboncombines with the oxygen of the sulphuric acid and of the baryta, andforms carbonic oxide, which escapes. The residue digested in waterforms a solution of sulphuret of barium. To the filtered liquor add hydro-chloric acid, which causes the evolution of hydrosulpliuric acid gas;filter the solution, evaporate, and crystallize. By re-solution, evaporation,and a second crystallization, the crystals may be obtained very pure andfine. Or sulphate of baryta may be decomposed by igniting it withchloride of calcium.
Properties. —Chloride of barium crystallizes in right rhombic platesor tables, sometimes in double eight-sided pyramids: the primary form ofthe crystals is the right rhombic prism. To the taste this salt is disagree-able and bitter. Its sp. gr. is 2 - 825. In dry warm air the crystals efflo-resce, but in the ordinary states of the air they undergo no change:When heated they decrepitate, lose their water of crystallization, and ata red heat fuse. At a white heat, according to Planiava, this saltvolatilizes. It is soluble in both cold and hot water : 100 parts of waterat 60° dissolve 43’5 of the crystallized salt,—at 222°, 78 parts. It isslightly soluble in ordinary rectified spirit, but is said to be insoluble inpure alcohol.
Characteristics. —That it is a chloride is readily known by nitrateof silver (vide p. 105.) The tests by which the nature of the base can bedetermined have been before mentioned (p. 338.)
Composition. —The crystals of chloride of barium have the followingcomposition:—
Barium .
Chlorine .
Water .
Eq.
. . . 1 . .. . . 1 . .. . . 2 . .
Eq.Wt.
. . 69 . .. . 36 . .. . 18 . .
Per Cent.
. . 56-09. . 29-26. . 14-63
Berzelius.
^ 85-201 . .14-799 . .
Phillips.
. . 85-5
. . 14-5
Cryst. Chlor. Barium . .
. . . 1 . .
. . 123 . .
. . 99-98
100-000 . .
. . 100-0
Purity. —The crystals should be colourless, neutral to test paper, per-manent in the ordinary states of the air, (if they become moist or deli-quesce, the presence of chloride of calcium, or chloride of strontium, maybe suspected), and their aqueous solution should undergo no alteration ofcolour by the addition of ferrocyanide of potassium, hydrosulphuric acid,