Porosity is induced in insulating refractories by adding________________?

A. Resistance to slag penetration
B. Resistance to CO attack
C. RUL
D. Permanent linear change

A. Removal of water of hydration
B. Vitrification
C. Decrease in crushing strength
D. Development of stable mineral form

A. Silica bricks
B. Fireclay bricks
C. Both A. & B.
D. Neither A. nor B.

A. Cristobalite
B. Tridymite
C. Quartz
D. None of these

A. Washing action of metal
B. Corrosion by layer of slag
C. Both A. & B.
D. Neither A. nor B.

A. Pottery furnace
B. Glass melting furnace
C. Crucibles
D. Gas retorts