Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: CHAPTER III THE DETERMINATION OF IRON IN ORES Many iron ores give up practically all of their iron to hydrochloric acid, provided that the acid be strong and the ore be very finely pulverized. 0n the other hand many ores contain a small amount of iron in such a state of combination that it will not dissolve in hydrochloric acid. In such cases the residue after treatment with acid must be fused and the iron determined in the fusion. If the residue after treatment with HCl is pure white with no dark specks, the iron is probably all dissolved unless-the ore contains TiO2 in which case an insoluble compound of iron, titanium and phosphorus, may remain which will not color the residue. Sometimes previous ignition of the ore will cause the ore to dissolve more completely in acid. All methods of analysis of iron in ores depend upon reducing the iron in acid solution to the divalent form then measuring the amount of a standard oxidizing agent required to oxidize the iron back to the triva- lent condition. The reducing agents are metallic Zn., metallic Al., SnCl2, H2S, S02. The oxidizing agents are K2Cr207 and KMn04. The Determination Of Ir0n By P0tassium Bichromate After Reduction Of The Ferric Chloride By Stannous Chloride The process depends upon the following reactions: 1. A strongly acid solution of FeCl3, if boiling hot, is almost instantly reduced to FeCl2 by a solution of SnCl2, the end of the reaction being shown by the disappearance of the yellow color of the ferric ion. 2FeCl3+SnCl2 = 2FeCl2+SnCl4. 2. Any slight excess of stannous chloride can be removed by adding HgCl2 forming a white precipitate of HgCl which is without action on iron salts or bichromate, the stannous chloride being oxidized to stannic chloride by the HgCl2. Sn.Cl2+2HgCl2 =...