Adding magnesium oxide to glass can improve refractive properties of glass,also glare can be converted into a softer visible light,which is critically important for the safety of the glass of planes and automobiles.

MgO 99% min
Acid-insoluble substance 0.1% max
Loss on ignition 2% max
Cl 0.05% max
SO4 0.5% max
Ca 0.05% max
K 0.008% max
Na 0.01% max
Fe 0.01% max
Mn 0.003% max
Pb 0.003% max
Packing density 0.4g/ml min