"He observed that the fumes of sulphur blacken ; he purified by means of arsenic and ; he made artificial rubies and other precious stones by tinting glass with metallic oxides; he described fluor spar as a flux for metals and their oxides; he oxidised sulphur with ; he knew that alcohol is obtained by distilling the fermented juice of sweet fruits; he proved that the acid extracted from and from ferrous sulphate (green vitriol) is the same as that obtained by burning sulphur with saltpetre, that is to say, it is sulphuric acid; and he discovered tin tetrachloride (stannic chloride), which is sometimes called Liquor fumans Libavii. It is a truly remarkable record of practical work, considering the age in which Libavius lived."