^{page no 466 note *} Jahres-Bericht, von Jacob Berzelius, 1848, p. 164, which contains a general comment on my researches of 1846.

^{page no 467 note *} They are specially referred to in the English translation of Lehmann's “Physiological Chemistry,” by Prof. G. E. Day, vol. i., p. 425. Cav. Soc. Publ. 1851.

^{page no 468 note *} Fourth edition of the English translation, 1855, p. 134, stated by its editor, Mr J. L. Bullock, to correspond with the eighth German edition. The process essentially consists in heating the silicated fluoride with oil of vitriol, and condensing the gaseous fluoride of silicon in aqueous ammonia, which after evaporation, re-solution in water, and desiccation, yields fluoride of ammonium. Fresenius recommends the addition of “some coarse pieces of marble to insure a continuous slight evolution of gas;” but I cannot approve of this recommendation, since the constant occurence of fluorine in shells and corals implies its presence in limestones; and the employment of marble for the purpose indicated risks the introduction of the very element for which we are seeking.