654 NEW YOEK STATE MUSEUM 



or sand is used. Tlie lime should be as free from impurities as 

 possible^ specially oxid of iron. 



Below are given two analyses, no. 1 from Blair county (Pa.) 

 and no. 2 from Sandusky (O.) The former is used for window 

 glass, the latter for lime flint glass. 



Organic matter .09 .05 



Silica 1.01 1 



Alumina 02 .4 



Ferric carbonate 165 



Magnesium carbonate 1.48 41 . 43 



Lime carbonate . 9*7 . 23 55.6 



Ferric oxid .12 



Moisture .4 



In. the manufacture of tableware lime furnishes a cheap substi- 

 tute for lead. 



Furnace flux 



This is one of the commonest uses of limestone. It is used as 

 a flux for both lead and iron ores.. In the blast furnace the 

 action of the limestone is to reduce the iron to its metallic state 

 and also flux the impurities, which pass off as slag. The purer 

 the limestone the more eflicient will be its action and the cheaper 

 its use, for it will be easily seen that the greater the percentage 

 of impurities the more limestone will be required to do the same 

 amount of work. For reasons of economy blast furnace operat- 

 ors often use less pure but more easily and cheaply obtained 

 limestones. 



Some time ago a table was prepared by J. M. Hartmann,^ 

 giving the value of limestone containing varying amounts of 

 fiilica, lime and magnesia. The basis of the calculation is mag- 

 nesian limestone at 56c a ton and fuel at $3.50 a ton, both at 

 the furnace. 



1 Mineral resources of U. S. 1883-84, p. 670. 



