The methods formerly employed in reducing ores were lixiviation and amalgamation with quicksilver, but modern methods are gradually coming into use.
ALKALI, an Arabic term originally applied to the ashes of plants, from which by lixiviation carbonate of soda was obtained in the case of sea-plants and carbonate of potash in that of landplants.
The latter operation furnishes an intimate mixture of the carbonate with charcoal, from which the carbonate is extracted by lixiviation with water and filtration.
The soluble salts are removed by lixiviation, and the residue is boiled with lime to form the soluble calcium ferrocyanide, which is finally converted into the potassium salt by potassium chloride or carbonate.
The lixiviation of the blackash requires great care, as the calcium sulphide is liable to be changed into soluble calcium compounds, which immediately react with sodium carbonate and destroy a corresponding quantity of the latter, rendering the soda weaker and impure.