Spiegeleisen is an alloy of

To obtain steel entirely free from sulphur and phosphorus,the process used is

What are the metals and their approximate percentages in German silver?

Consider the following metallurgical processes:
$I$. Heating impure metal with $CO$ and distilling the resulting volatile carbonyl (b.p. $43 \ ^oC$) and finally decomposition at $150 \ ^oC - 200 \ ^oC$ to get the pure metal.
$II$. Heating the sulphide ore in air until a part is converted to oxide and then further heating in the absence of air to let the oxide react with unchanged metal sulphide.
$III$. Electrolysis of the molten electrolyte containing approximately equal amounts of the metal chloride and $NaCl$ to obtain the metal.
The processes used for obtaining magnesium,nickel and copper are respectively:

Bell metal is an alloy of

Explain the following:
$(a)$ $CO_2$ is a better reducing agent below $710 \ K$ whereas $CO$ is a better reducing agent above $710 \ K$.
$(b)$ Generally,sulphide ores are converted into oxides before reduction.
$(c)$ Silica $(SiO_2)$ is added to the sulphide ore of copper in the reverberatory furnace.
$(d)$ Carbon and hydrogen are not used as reducing agents at high temperatures for certain metals.
$(e)$ Vapour phase refining method is used for the purification of $Ti$.