Calcination of iron ores is done ______

after dressing

by roasting in heaps

to remove carbonic acid

All of the above

Correct Answer : All of the above

Explanation :

* after dressing

* by roasting in heaps

* to remove carbonic acid
* to remove moisture

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The proportions of charcoal, saltpetre and sulphur in gun powder by weight, are respectively :

75, 10, 15

10, 15, 75

15, 75, 10

10, 75, 15.

Correct Answer : Option (C) : 15, 75, 10

A 1st class brick immersed in water for 24 hours, should not absorb water (by weight) more than ____

10%

15%

20%

25%

Correct Answer : Option (C) : 20%

According to IS 399-1963, the weight of the timber is specified at ______

12% moisture content

14% moisture content

8% moisture content

10% moisture content

Correct Answer : Option (A) : 12% moisture content