648 GEOLOGY AND MINING INDUSTRY OF LEADVILLE. 



alkali and boiled with an excess of hyposulphite of soda, which precipitates titanic 

 acid, alumina, and a little soluble silica. The precipitate collected on a filter, washed 

 thoroughly and calcined, is treated in a platinum vessel with a mixture of sulphuric, 

 hydrochloric, and hydrofluoric acids, and the whole is evaporated to dryness. The res- 

 idue is fused with bisulphate of potash, and titanic acid is extracted, as usual, by boil- 

 ing the dilute solution. 



Although magnetic oxide of iron is reported in the analysis with the formula 

 Fe 3 O 4 , this is not exact. The writer succeeded in isolating this oxide in a state of great 

 purity by alternately extracting it with the magnet and rubbing it with the finger on fil- 

 ter paper until it no longer soiled the paper, to which the non-magnetic oxides remained 

 attached. It was then analyzed, and its composition is represented by the formula 

 Fe 20 O 27 =G(FeO)+7(Fe 2 O 3 ), instead of 7(FeO)+7(Fe 2 O 3 ), which would be equivalent to 

 the formula Fe 3 O 4 . It is only quite natural that magnetic oxide formed in the midst 

 of peroxide of iron should contain an excess of this oxide. The writer assumes that 

 the force of adhesion was used for the first time in this instance for the mechanical sep" 

 aration of substances. It has been employed since in connection with the use of the 

 magnet in investigations on the nature of different metallurgical products, and in ench 

 case it has led to interesting results. 



QBE-BEDS. 



Smelting charges consist of mixtures of ore with fluxes and fuel in definite but 

 somewhat varying proportions, previously determined, so as to produce a desired 

 chemical combination. 



The ore entering into the smelting charge may be an unmixed ore of known 

 composition, or a previously-prepared mixture of ores, called an ore-bed, or a combi- 

 nation of the two. 



t're-beds are prepared by superposing layers of different ores of known weight 

 and composition in such proportion as to produce mixtures of known contents in lead, 

 silver, iron, and silica. 



Composition of ore-beds Ore-beds are generally made to contain equal parts of 

 metallic iron, metallic lead, and silica or gangue, or from 20 per cent, to 25 per cent, 

 of each. The relation between lead and silver is about six pounds of lead to one ounce 

 of silver; but this relation often varies, as well as the percentage of lead, while, on the 

 contrary, the percentage of iron and gangue remains pretty constant. 



The great advantage derived from the preparation of ore-beds, besides giving 

 mixtures of known composition, is that of drying the ore, an operation which if carried 

 on in the furnace would absorb an enormous amount of heat. 



In Table V will be found the following particulars in regard to seven different 

 ore-beds : 



1. Humid weight of each ore-bed iu pounds. 



2. Average percentage of moisture for each ore-bed. 



3. Dry weight of each ore-bed in pounds. 



4. Percentage of silica or gaugue for each ore-bed. 



5. Total weight of silica iu pouuds for each ore-bed. 



6. Percentage of iron for each ore-bed. 



7. Total weight of iron iu pounds for each ore-bed. 



8. Average tenor of silver in ounces to ton for each ore-bed. 



9. Total weight of silver in ounces for each ore bed. 



10. Percentage of lead for each ore- bed. 



11. Total weight of lead in pounds for each ore-bed. 



