PERCOMPOUNDS OF IRON. 563 



mixing the protosulphuret with half its weight of sulphur, and 

 distilling in a retort by a temperature short of redness. The 

 metallic sulphuret combines with a quantity of sulphur equal to 

 what it already possesses, and forms a bulky powder of a deep 

 yellow colour and metallic lustre, upon which sulphuric and 

 hydrochloric acids have no action. This sulphuret appears to 

 be of a stable nature, but the lower sulphurets of iron oxidate, 

 when moistened, with great avidity. Stromeyer found the 

 native magnetic sulphuret of iron to consist of 100 parts of iron 

 combined with 68 of sulphur ; and the sulphuret left on distil- 

 ling iron with sulphur, at a high temperature, to be of the same 

 composition. It may be viewed as 5Fe S + Fe 2 S 3 (Berzelius.) 

 It is said to be this compound which is almost always formed 

 when sulphuret of iron is prepared. 



Perchloride of iron, Fe 2 C1 3 , is formed when iron is burned 

 in an excess of chlorine. It is volatile at a red heat. Its solu- 

 tion, which is used in medicine, is obtained by dissolving the 

 hydrated peroxide of iron in diluted hydrochloric acid. When 

 greatly concentrated, the solution of perchloride of iron yields 

 at one time orange yellow crystalline needles, radiating from a 

 centre, which are Fe 2 C1 3 - L 12HO; at another time, large dark 

 yellowish red crystals, Fe 2 Cl 3 + 5HO (Mitscherlich, Lehrbuch 

 II. 498.) Mixed with sal ammoniac, and evaporated in vacuo, 

 it affords beautiful ruby red octohedral crystals, consisting of 

 2 eq. of chloride of ammonium, and 1 eq. perchloride of iron, 

 with 2 eq. of water, Fe 2 C1 3 , 2N H 4 Cl-f 2HO. Of this water, 

 the double salt, I find, loses 1 eq. at 150, and the other when 

 dried above 300. There is a similar double salt, containing 

 chloride of potassium, but not so easily formed. The per- 

 chloride of iron is soluble both in alcohol and ether. A strong 

 aqueous solution was found by Mr. Phillips to dissolve not less 

 than 4 eq. of freshly precipitated hydrated peroxide of iron, 

 becoming deep red and opaque. 



Periodide of iron is formed in similar circumstances as the 

 preceding perchloride. 



Percyanide, or stsquicyanide of iron, Fe 2 Cy 3 , is unknown 

 in a pure state. A solution of it, which is decomposed by 

 evaporation, is obtained by precipitating the potash of the red 

 prussiate by the fluoride of silicon. It forms a numerous class 

 of double cyanides. A compound of the two cyanides of iron, 

 like the compound oxide, is obtained as a green powder, when 



