in Analysis, and Separation of Oxides of Iron, etc. 371 



of certain chlorides at comparatively low temperatures) to con- 

 vert ferric oxide completely to ferric chloride by the action of 

 gaseous hydrochloric acid at about 200° C. At this tempera- 

 ture the greater part of the iron sublimed, but a residue 

 remained, which, volatilizing neither on long heating at 200° 

 nor upon considerable elevation of the temperature, proved 

 upon examination to be ferrous chloride. In the experiments 

 to be described we have acted with gaseous hydrochloric acid 

 upon ferric oxide made by igniting the nitrate prepared from 

 pure iron deposited electrolytically by high currents passing 

 between electrodes of platinum in a strong solution of ammonio- 

 ferrous sulphate. The oxide, contained in a porcelain boat, 

 was heated within a roomy glass tube over a small combustion 

 furnace. The hydrochloric acid (generated by dropping sul- 

 phuric acid into a mixture of strong hydrochloric acid and 

 salt, and dried by calcium chloride) entered one end of the 

 tube and passed out at the other through a water trap. In 

 early experiments a high-reading thermometer was inserted 

 through the stopper in the exit end of the tube so that its bulb 

 was above and immediately adjacent to the boat carrying the 

 oxide. In this way the actual temperatures of the vapors 

 about the boat were fixed with considerable accuracy ; later, 

 after a little experience in gauging the effect of the burners, it 

 was found that the temperatures could be regulated very 

 closely without actually depending upon the thermometer. 

 We found, as did Moyer, that ferric oxide, submitted to the 

 action of dry hydrochloric acid gas, volatilizes partially as ferric 

 chloride at low temperatures — 180° to 200° C. — leaving ulti- 

 mately a crystalline'residue which does not change visibly when 

 heated for an hour or two at 200°, or even at 500°, in the pure 

 dry acid. According to our experience, this residue is generally 

 slightly reddish or salmon-colored ; but sometimes, especially 

 after a second heating, the boat having been withdrawn from 

 the tube or exposed to the atmosphere (and so to moisture), the 

 residue is white. When it is white it dissolves in water, 

 yields the characteristic reaction for a ferrous salt with potas- 

 sium ferricyanide, gives no reaction with potassium sulpho- 

 cyanide, and upon treatment in weighed amount with potassium 

 permanganate destroys the amount of that reagent theoretically 

 required for its oxidation upon the supposition that it is fer- 

 rous chloride. The slightly colored residue when treated with 

 water yields a solution showing the reaction of a. ferrous salt 

 only, but when treated with hydrochloric acid and then tested 

 shows the presence of a trace of iron in the ferric condition. 

 Doubtless the coloration of the residue is due to an included 

 trace of ferric oxide or oxy chloride, which after exposure of 

 the containing crystals to slight atmospheric action, is more 



Am. Jour. Sci.— Fourth Series, Vol. VII, No. 41.— May, 1899. 

 25 



