yo 0/1 the Combliiatlons of the Metals tvlth Sulphur. 



It is known, In fa(f>, thst when a large quantity of water is added to t^ei^ concentrated 

 foiutions, very cohfidcrable precipitates arc formed, which have been mifl^kenly fuppofed 

 to be pure metallic oxides, but which are really falls, containing a portion of acid ftrongly 

 adherent, that cannot be completely feparated but by means, of an alkali. 



So that we may confider the combinations formed by thefe metals, and probably many 

 others alfo with the acids, as neutral falts diffolved by a fuper-abundance of acid, which 

 is taken from them by the water, and confequently the falts fall down truly neutral and 

 infoluble. 



From the manner in which the muriatic acid a£ts on the metallic fulphurets, it follows, 

 tliat the more the metals which compofe them abforb of oxigen to unite with this acid, 

 the lefs there remains of fulphur after the folution, and vice verfa ; but if thefe metals 

 abforb little oxigen, if they contain much fulphur, and if alfo their affinity for oxigen be 

 jnconfiderable, the totality of the metal will never be feparated from the fulphur by the 

 muriatic acid, becaufe in proportion as this combuftible body becomes more abundant, it 

 oppofes by its mafs the folution of the metal, and hence it is that certain metallic fulphu- 

 rets which are not attacked by the muriatic acid, yield to that force, after a portion of 

 their fulphur has been feparated by diftillation. 



The mode of aftion of the nitric acid on the metallic fulphurets is very different, and 

 though the fulphur is not in this cafe attracted by any fubftance, neverthelefs it is com- 

 pletely feparated from the metal, and falls down perfedlly pure if the operation have been 

 properly performed ; but though the combination of the" nitric acid with the metal is not 

 afilfted by hidrogen, as happens' with regard to the muriatic acid, yet this firft acid yields 

 oxigen to the metal more eafily than water ; and it is by virtue of this affinity of oxigen 

 for the metal and the oxide which is formed for the undecompofed acid, that the folution 

 is efFedled. So that in all the inftances when metallic fulphurets are decompofed by the 

 nitric acid, there is conftantly a formation of nitrous gas, and never of fulphurated 

 hidrogen. 



It appears in general, that fulphur has a ftronger affinity with the metals than with their 

 oxides, and that this affinity diminlfhcs in proportion to the quantity of oxigen they abforb. 

 There are even fome which do not unite with fulphur but in the complete metallic ftate. 

 Thus for example, by triturating the brown oxide of lead with fulphur, a portion of the 

 fulphur takes fire, and the other portion combines with the lead thus reduced to the 

 metallic ftate. 



' It appears alfo that zinc does not unite vith fulphur when it is completely metallic, or 

 at leaft that nature has not yet prefented inftances of this, nor has art fucceeded in com- 

 bining thefe two fubftances. That which is known in mineralogy by the name of Blende, 

 0* fulphurated zinc, has been miftakenly regarded by fome mineralogifts as a combination of 

 zinc with fulphur. It is on the contrary a fulphurated oxide of zinc, which very frequently 

 contains hidrogen j for the blendes are almoft always foluble in acidS) and produce fulphu- 

 rated 



