[92] Repertorium der analyt. Chemie 1885, Vol. 5, p. 178.
[93] Compare Matthes & Müller, Z. U. N. 1906, Vol. 12, p. 90 et seq.
[94] Almost a tenth part of the ash of the shells consists of silica.
[95] cf. Moeller Mikroskopie der Nahrungs-und Genußmittel. Berlin. 1905. II part Springer p. 412.
[96] Ztschr. öffentl. Ch. 1899, p. 27.
[97] German patent No. 71, 373, 8th. January 1873.
[98] Engl. Patent No. 14624, June 16th. 1897.
[99] Pharm. Rundschau 1898, p. 781.
[100] Ztschr. für chemische Industrie 1878, p. 303, German Patent No. 2112, Sept. 24th. 1878.
[101] Annales de Chimie et de Physique, Vol. 183, p. 423.