SULPHURETS. 353 



It cannot.be doubted, that many of the compounds which were 

 formerly regarded as sulphurets of the oxides of metallic bases, were 

 really sulphurets of the metals themselves, and it is now clearly as- 

 certained that they are formed in the following modes and circum- 

 stances. 



1. By fusion of the metallic base with sulphur, or by passing its 

 vapor over the metal, ignited in a porcelain tube; the union often 

 takes place with the disengagement of much heat and light, resem- 

 bling a combustion, and by many it is regarded as such. Potassium 

 and sodium are the only alkaline bases which we are able to try in 

 this way ;* the same thing happens with silicium. 



2. By heating the metallic bases in sulphuretted hydrogen gas, 

 when the sulphur combines with the metal, often with appearance of 

 combustion, and the hydrogen gas is liberated ; potassium and sodi- 

 um exhibit this phenomenon remarkably. 



3. By passing the same gas, or its solution in water, into the metal- 

 ic solution, when sulphurets are precipitated ; those metals that are 

 not affected by sulphuretted hydrogen, namely, iron, manganese, 

 nickel, cobalt and uranium, are, like all the other metallic solu- 

 tions, precipitated as sulphurets, by the hydro-sulphurets of potassa 

 and ammonia. 



4. By heating sulphur to ignition with the oxide of the metal; the 

 oxygen escapes in sulphurous acid, and the remainder of the sulphur 

 combines with the metal. 



5. By igniting the sulphate of an alkaline oxide with charcoal 

 powder, j- or by passing the hydrogen gas over the ignited sulphate ; 

 all the sulphates of these bodies are thus reduced at a white heat and 

 if fusible, very quickly. Perhaps the true limit between the sul- 

 phurets of the fixed alkalies and alkaline earths, and of their metallic 

 bases, will be found below a red heat for the former, and at or above 

 it for the latter. There cannot be any doubt that true metallic sul- 

 phurets are formed, when the alkalies and alkaline earths are igni- 

 ted with sulphur, or when a sulphate is decomposed, at a similar 

 temperature, by charcoal or hydrogen. { 



It is remarkable that during the decomposition of the sulphates by 

 charcoal, the gases disengaged are found to contain the whole of the 



* Of the common metals a number, as iron, copper, lead and bismuth, exhibit this 

 phenomenon in a striking manner; the two former shew it in a glass vessel. 



t Mr. Berthier enclosed the sulphate in a covered crucible lined with a mixture of 

 clay and charcoal powder. 



t The limits of this work do not allow me to cite more in detail, the labors of Vau- 

 quelin, Ann. de Chim. et de Phys. Vol. VI, 1817, or those of Gay-Lussac, Id. or 

 of Berthier, Id. Vol. XXII, or of Berzelius, Vol. XX. A perspicuous statement 

 drawn from these authorities, may be found in Dr. Turner's Chemistry, 2d Ed. 

 p. 388 ; I find that it contains every thing of importance in the original memoirs. 



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