On defiiiite Proportions. 



sr») 



100 parts of.ron were comblnecl with 117 of sulphur, and 

 sulpl'uret of iron at a maximum [or super-sulphuret ot 

 iron] consists of 



Iron 46-OS 100 



Sulphur 53-92 117 



The combination of \00 parts of iron with 58| of sul- 

 phur in the former and in the latter case 117-2, that is 

 -3 parts less than a double portion, indicates some sligh 

 inaccuracy in one of the experiments If we assume that 

 the silica, found in the pyrites, existed in a metallic state, 

 which is a very probable supposition, we must calculate on 

 •04 only of the base, or of silicium ; and the sulphur com- 

 bined with 100 pans of iron will be 117-5, that is precisely 

 according to the calculation ; neglecting, at least the small 

 quantity of sulphur which may have been combined with 

 the silicium, if these bodies have any affinity for each 



° ifmay be considered as tolerably well established, that 

 no other combinations take place between iron and sulphur 

 than the two which are here examined. Yet we often hnd, 

 in preparing the artificial pyrites, products which are dif- 

 ferently constituted. This was the case, tor example m 

 my analysis of sulphuretted hydrogen (Afh. ii. 86.) I he 

 sulphureited iron, which I then employed for obtaining the 

 eras, contained 36| of sulphur to 100 of iron. In general, 

 I have found in the preparation of the sulphuret at a maxi- 

 mum by ignition in close vessels, that when the mass was not 

 brouf^ht into fusion, the iron always retained a greater quan- 

 tity o'f sulphur, than the sulphuret at a minimum contains. 

 In two different experiments, I found this excess of sulphur 

 pretty constant ; in one, 100 parts of iron had retained 68-6, 

 in another, 68-2 of sulphur. If in the preparation of the 

 sulphuret we employ iron in excess, a portion of the metal 

 is dissolved by the sulphuret, and the solution may vary by 

 imperceptible gradations, like that of a salt in water. It 

 this were not the case, the whole doctrine, which is sup- 

 ported by so many experiments, must be merely a ground- 

 less imagination. [The solubility of a metal and its oxides 

 in the sulphuret, in all proportions, was observed by 1 roust 

 in his experiments on metallic sulphurets, especially with 

 respect to antimony. — Gilbert.'] _ 



We have seen that the sulphuret of lead, and in all pro- 

 bability that of copper also, become neutral salts by oxy- 

 genization. It is now to be inquired if the same is true of 

 the sulphuret of iron. ^^ ^ 



* S-l XI. SuL- 



