“…29 shows, the substitution of SiO 2 for Al 2 O 3 leads to varying viscosity maxima for different slags at 1300°C. The viscosities [84,89] of the slag 10, slag 11 and slag 12 are satisfactorily reproduced. It is found that the substitution of CaO for Na 2 O causes a right shift in position of the viscosity maximum at constant contents of MgO and K 2 O.…”