^06 



CHEMICAL MANUEES. 



TABLE LVIL— ANALYSES OF BLACK NEEDLES, MAGNETIC AND 

 NON-MAGNETIC, FOUND IN BASIC SLAG. 



Lime . 

 Magnesia . 

 Alumina 

 Ferric oxide 

 Ferrous oxide 

 Manganous oxide 

 Chromium sesquioxide 

 Vanadium oxide 

 Silica . 

 Phosphoric acid 



99-826 



100-109 



According to these authors, these crystals would therefore consist 

 chiefly of ferrite and of aluminate of lime. The analyses of the blue 

 crystals give : — 



TABLE LVIII. 



-ANALYSES OF BLUE CRYSTALS FOUND IN BASIC 

 SLAG. 



These figures correspond exactly with the formula — 



8PA, SSiO.,, 36CaO, FeO, A1,0, 



By replacing small quantities of oxide of iron and alumina by 

 equivalent amounts of lime, a more simple formula is arrived at, 

 P0O5, SiO^S, CaO, which may also be written — 



PA> 3CaO + SiO.,, 2CaO 

 Hilgenstock and Carnot have examined the order of formation of 

 the crystals, and both have come to the same conclusions. 



The first crystals which are formed appear to be the rectangular 

 tablets on which afterw^ards come the brow^n hexagonal needles. It 

 is only later that the rest of the slag, becoming richer in silica, iso- 

 lates the blue and brilliant crystals. These are superposed by the 



