Chemistry, 357 



dorff's An. ix. 6 19-) — On adding sulphuric acid to a mixture of the com- 

 mon mineral chameleon with half its weight of fluor-spar in powder, a 

 violent action ensues, and a beautiful purple coloured vapour is disengaged. 

 On performing this experiment with fuming sulphuric acid in a vessel 

 of platinum, the vessel became filled with a greenish yellow gas, of a 

 more intensely yellow tint than chlorine. When this gas was mixed with 

 common atmospheric air, it instantly acquired the purple-red colour. By 

 water it was freely absorbed, and the solution was of a purplish red co- 

 lour, and had an acid reaction. The yellow gas acted instantly on glass ; 

 fluo-silicic gas was formed, and a brown matter deposited, which became 

 of a deep purple-red colour on the addition of water. 



From the experiments of Dr Wohler it may be inferred, that the yel- 

 low gas is a fluoride of manganese ; that when mixed with water both 

 compounds are decomposed, and fluoric and manganesic acids are formed, 

 which are dissolved ; that a similar formation of the two acids ensues from 

 the admixture of the yellow gas with atmospheric air, owing to the mois- 

 ture contained in the latter ; and that by contact with glass fluo-silicic gas 

 is generated, and anhydrous manganesic acid deposited. Dr Wohler has 

 not been able to ascertain any other of its properties, nor is it certain 

 whether it is the vapour of a volatile liquid, or a gas permanent at mode- 

 rate temperatures. 



This is obviously the same compound which M. Dumas noticed in his 

 experiments on the volatile chloride of manganese. (See the Number of this 

 Journal for January, p. 179.) The fluoride must doubtless contain as 

 many equivalents of fluorine as the manganesic acid does of oxygen. 



16. Preparation of Pure Malate of Lead. (Poggendorff, Ibid,) — Dr 

 Wohler states that a perfectly pure malate of lead is readily obtained by the 

 following process : The juice of the berries of the service tree, before they 

 are quite ripe, is diluted with three or four parts of water, filtered, and heat- 

 ed ; and while boiling a solution of acetate of lead is added as long as any tur- 

 bidity appears. The solution is then quickly filtered. At first a small 

 quantity of dark-coloured salt subsides ; but on decanting the hot liquid, 

 the malate of lead is deposited on cooling in groups of brilliant white crys- 

 tals 



17. Decomposition of Selenious Acid by Metals. By Professor Fischer 

 of Breslau. (Poggendorff, x. 152.) — Berzelius had observed that the se- 

 lenious acid in solution is reduced to the state of selenium by the action 

 of metallic zinc. Professor Fischer has remarked, that the whole list of 

 metals from zinc to silver inclusive, possesses the same property. Silver is 

 even an exceedingly delicate reagent for selenious acid, and detected its pre- 

 sence when purposely mixed with 50,000 parts of sulphuric acid. Selenious 

 acid has been thus discovered in three kinds of sulphuric acid of commerce. 

 The procedure consists simply in placing a rod of silver in the acid or so- 

 lution to be tested; and after a longer or shorter period the metal ac- 

 quires a dark film on its surface, like that produced by sulphuretted hy- 

 drogen. The compound thus formed is seleniuret of silver. 



