When the perchloride is produced in a large tube, its vapour gradually displaces the air present, and the tube becomes filled with it; if it then be poured into a jar with moistened sides, the colour of the gas changes as it comes into contact with the moist air; a thick smoke of a fine rose colour appears; and the sides of the vessel acquire a deep purple colour due to the manganesic acid formed. The water thus coloured is abundantly precipitated by nitrate of silver, and, acted upon by a solution of potash, produces all the changes of the mineral chamelion.
The most simple process for the preparation of this body appears to be to form a common green chamelion, to convert it into red chamelion by sulphuric acid, and to evaporate the solution, which will give a residue consisting of sulphate and manganesate of potash. This mixture, acted upon by concentrated sulphuric acid, produces the solution of manganesic acid, into which the common salt is to be thrown in small pieces, until the vapours which rise are colourless; the latter effect is a sign that all the manganesic acid is decomposed, and that muriatic acid only is produced.
An analogous compound is formed when a fluoride is used in place of the common salt. But all attempts as yet made to collect a sufficient quantity for examination have failed; the chloride, on the contrary, is easily formed and examined, although it is not so easy to preserve it.—Annales de Chimie, xxxvi. 81. [p476]
[132] Query, what is a permanent gas?—ED.
20. Preparation of pure Oxide of Zinc, by M. Hermann.
21. Deuto-Sulphuret of Cobalt.
22. Separation of Bismuth from Mercury by Potassium.
Copper, lead, tin, and silver, are equally separated, but not so promptly, or so evidently to the eye as bismuth; for they are not associated with divided mercury, at the time of their separation, like the latter: with bismuth a mere atom is rendered visible, and M. Serullas thinks that chemistry does not present a more delicate test than the amalgam of potassium for bismuth in mercury.—Annales de Chimie, xxxiv. 195.
23. Sulphuret of Arsenic proportionate in Composition to Arsenic Acid.
M. Pfaff further says that arsenic acid may be separated from its combinations with bases, by dissolving the arseniates in nitric acid, and passing sulphuretted hydrogen through the solution; an abundant precipitate of sulphuret of arsenic is formed, containing no trace of the base of the arseniate decomposed.—Bull. Univ. A. viii. 256.