234 J' S. L. VOGT 



Extremely thin. — Basic slags with predominant MnO, as 



SiO^ MnO FeO ALO3, CaO, etc. 



3c^4S 30-40 5-25 0-4 



With the exception of certain siKcate melts rich in PbO, melts 

 rich in MnO are the thinnest silicate melts I know, and they are 

 also extremely thin at the temperatures immediately above or at 

 the beginning of crystallization (of manganese-f ayahte or rhodonite) . 

 In the common silicate slags with as much MnO as 10-15 P^r cent, 

 MnO causes a noticeable increase in thinness. 



Exceedingly thin. — Basic slags with predominant FeO, as 



SiO^ FeO CaO, MgO, ALO3 



25-30 60-70 ^ -^ ' ^^^• 



These are also very thin, even when cooled to the beginning 

 of the crystallization (of fayalite). 



In slags with predominant FeO, the viscosity is somewhat 

 greater when the percentage of SiOz rises to 40-45 per cent, and the 

 viscosity is considerably increased when the percentage of SiOa 

 rises above 55 per cent. 



In the common CaO+MgO slags with some AI2O3, FeO causes 

 an increase of thinness, hardly however to the extent shown by 

 those with MnO. 



Very thin at about 1,400°. — Middle basic melts with approximately 

 equal proportion of CaO and MgO, 



The thinness seems to increase somewhat when CaO is replaced 

 in part by MgO. This may not be maintained with absolute 

 certainty, however. 



In an intermediate mixture of CaO and MgO, the viscosity 

 increases with increase of Si02,when SiOa amounts to more than 

 50 per cent. 



