Work continued on alternative sclerosants in the early 20th century. During that time carbolic acid and perchlorate of mercury were tried and whilst these showed some effect in obliterating varicose veins, side-effects also caused them to be abandoned. Prof. Sicard and other French doctors developed the use of sodium carbonate and then sodium salicylate during and after the First World War. Quinine was also used with some effect during the early 20th century. At the time of Coppleson's book in 1929, he was advocating the use of sodium salicylate or quinine as the best choices of sclerosant.