MICROCHEMICAL REACTIONS OF IRON 409 



bismuthate. A beautiful pink or purple color is developed due 

 to the permanganate formed. 



To complete the test add a fragment of rubidium chloride, 

 stir, add a drop of water and allow a drop of perchloric acid to 

 flow into the drop. Crystals of rubidium perchlorate are imme- 

 diately formed, taking up the permanganate in solid solution and 

 yielding pink or purple crystals. This test requires great care 

 in the adjustment of the concentrations in the second half of the 

 test. A pink or red color upon the first addition of the bismuth- 

 ate is usually sufficient to indicate that Manganese is present. 



EXPERIMENTS. 



Test this method first upon pure Mn salts, then upon mixtures of other elements 

 with Mn. 



IRON. 



Crystal Forms and Optical Properties of Common Salts 

 of Iron. 



A. ISOTROPIC. Iron alums (I). 



B. AN ISOTROPIC. 



Hexagonal. Chloride (when sublimed). 



Tetragonal. 



Orthorhombic. Ammonium-ferric chloride; oxa- 

 late (ous). 



Monoclinic. Sulphate (ous) ; 1 ammonium-ferrous 

 sulphate; sodium-ferric oxalate; potassium- 

 ferric oxalate. 



Triclinic. 



DETECTION. 



A . By Means of Potassium Ferrocyanide. 



To the test drop, apply a fragment of the reagent by 

 Method III , page 300. 



A dark b ue precipitate or color indicates iron. The precipitate 



is soluble in alkalies, insoluble in acids. It is therefore always best 



to acidify with hydrochloric acid before adding the ferrocyanide. 



The presence of much copper may seriously interfere with the 



test because of the formation of brown copper ferrocyanide. 



1 But if magnesium sulphate is present, orthorhombic. 



