The flux is moistened with water and exposed to a current of carbonic acid, which, on account of the condensing action of the charcoal, is absorbed with great avidity.
In the Carboniferous Limestone series, the purer kinds of limestone are used for the manufacture of lime, bleaching powder and similar products, also as a flux in the smelting of iron; some of the less pure varieties are used in making cement.
In short, its duty is to " flux " the gangue and ash, and wash out the sulphur.
If, argued Protagoras in a treatise entitled Truth, all things are in flux, so that sensation is subjective, it follows that " Man is the measure of all things, of what is, that it is, and of what is not, that it is not "; in other words, there is no such thing as objective truth.
The use of oxide of lead in glass-making was no new thing; it had been used, mainly as a flux, both by Romans and Venetians.