For existence of aquatic life in water, the dissolved oxygen content in it, should not be less than ________ ppm?

Higher boiling fractions like atmospheric residue is distilled under vacuum at low temperature because at high temperature, there is a tendency of the predominance of ________?

The main function of a muffle in the muffle furnace is to________?

Coal containing large quantity of ________ are difficult to wash?

The usual energy consumption in electric arc furnace steel making is ________ KWh/ton of steel?

Which of the following size reduction equipments employs mainly attrition for ultrafine grinding?