398 Miscellanies. 



purulent sores or putrescent wounds, it soon deprives them of their 

 bad odor, and prevents the ulterior developement of fetid matter. 

 These effects cannot be ascribed altogether to porosity, or it would 

 cease by prolonged contact; but regarding the action as electro- 

 motive, it establishes in these wounds, electric states, which destroy 

 the affinities that give rise to putrefactive or purulent compounds. 

 Annales de Chimie^ JVov. 1829. 



41. On the dark precipitate of Platina of Ed. Davy^ and on the 

 property of spongy Platina^ hy M. Liebig. — The black precipitate 

 of Davy is obtained by heating the sulphate of the oxide of platina 

 with alcohol. This substance when dried emits an ethereal odor, and 

 possesses the remarkable property of becoming red hot when mois- 

 tened with spirit of wnne, and continuing so as long as the alcohol re- 

 mains. Acetic acid is formed during the ignition. 



M. Doebereiner ascertained that this substance absorbs all the 

 combustible gases, but does not absorb either oxygen or carbonic acid. 

 Saturated with hydrogen and placed in contact with oxygen, it effects 

 their combination, and becomes incandescent. Presuming that finely 

 divided platina might possess the same property, he tried it, and thus 

 discovered the remarkable inflammation of hydrogen by spongy pla- 

 tina. 



The best mode (according to the author) of obtaining the black 

 precipitate, is to procure the chhruref (chlorure) of platina, by heat- 

 ing strongly, and for a long time, the chloride of the same metal, and 

 to treat this chloruret, which has a greenish yellow color, with a 

 concentrated solution of potash. It forms with heat a perfect solu- 

 tion, dark and thick, into which alcohol is to be poured by slow de- 

 grees, shaking it well. In a short time it effervesces strongly, dis- 

 charges much carbonic acid, and a very heavy velvet-black powder 

 subsides, which must be boiled successively with a little alcohol, hy- 

 drochloric acid and potash, and lastly four or five times with water, 

 and then washed and dried in a porcelain capsule, without coming in 

 contact with a filter or any organic substance. 



This dark powder is granular and hard, and loses no weight by 

 being strongly calcined in the air. It dissolves in aqua regia, and 

 gives a limpid solution, which contains only chloride of platina. 

 Moistened with spirits of wine, it quickly ignites, and produces acetic 

 acid; placed in a receiver filled with oxygen, over mercury, and 



