267. The sequence of refractory materials according to increasing melting points is :
A. Dolomite, Magnesia, Bauxite, Chromite
B. Bauxite, Chromite, Dolomite, Magnesia
C. Magnesia, Bauxite, Dolomite, Chromite.
D.

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268. The high quality refractory materials which contain pure clay are oxides of
A. pure alumina oxide
B. pure magnesia oxide
C. pure carbides
D. all of these.

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269. Pick up the metal refractory from the following :
A. Molyblendum
B. Tungsten
C. Zicronium
D. All of these.

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270. The usual percentages of clay and metal in cermet are:
A. 50%,50%
B. 60%,40%
C. 70%,30%
D. 80%,20%.

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271. Pick up the constituent of good brick earth whose excess causes the raw bricks shrink and warp during drying and burning, from the following :
A. Alumina
B. Lime
C. lronoxide
D. Magnesia.

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272. A good brick earth should contain :
A. about 20% to 30% of alumina
B. about 50% to 60% of silica
C. not more than 5% of lime
D. All the above.

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273. For preparing porcelains, the clay should be
A. sufficiently pure
B. of high degree of tenacity
C. of good plasticity
D. All the above.

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