ALKALI MANUFACTURE - MANUFACTURE OF SALT CAKE By this name is known the residue resulting from the treatment of salt with strong sulphuric acid in the manufacture of hydro chloric acid (q.v.). It consists of sodium sulphate with a small proportion of free sulphuric acid. Apart from the strictly utilita rian view, this product has an interest inasmuch as its ture, together with that of sodium sulphide, is the only surviving part of the celebrated Le Blanc soda process (see LE BLANC,