^{page 145 note *} Literary Gazette, Dec. 2. 1843, p. 779.

^{page 145 note †} Annales de Chimie, tome lvii. (1806), p. 43Google Scholar.

^{page 145 note ‡} Ibid., p. 44.

^{page 145 note §} Ibid., tom, lv., p. 265.

^{page 145 note ∥} Ibid., p. 258.

^{page 145 note ¶} Ibid.

^{page 146 note *} Annales de Chimie, tom. lxi. (1807), p. 256Google Scholar.

^{page 146 note †} Ibid., 1806, t. lvii., p. 41.

^{page 146 note ‡} Chemistry of Animal Bodies, p. 236.

^{page 146 note §} Guy's Hospital Reports, quoted in Edin. Phil. Journal, vol. xxviii., p. 93.

^{page 146 note ∥} Chemical Society's Memoirs, vol. ii., p. 135.

^{page 146 note ¶} Ibid., p. 101.

^{page 146 note **} Edin. Phil. Journal, vol. xxxix., p. 235.

^{page 146 note ‡} Ann. de Chim., t. ix. (1843), p. 381Google Scholar.

^{page 146 note ‡‡} Quarterly Journal of Geological Society, vol. i., p. 216.

^{page 146 note §§} Ibid.

^{page 146 note ∥∥} Ann. de Ch. et Ph., t. ix., p. 375, 1843Google Scholar.

^{page 147 note *} Quarterly Journal of Geological Society, vol. i., p. 216.

^{page 147 note †} Annales de Chimie, 1843, pp. 370–78.

^{page 147 note ‡} Ibid., t. lxi., p. 257.

^{page 147 note §} Literary Gazette, 1843, p. 779.

^{page 147 note ∥} Chemistry of Agriculture, 3d edition, p. 123.

^{page 148 note *} Quarterly Journal of Geology, vol. i., p. 215. Mr Middleton's other papers on fluorine are in the Chemical Society's Memoirs, vol. ii., p. 134; and in the London Phil. Mag., No. 164, p. 14.

^{page 149 note *} Edin. Phil. Jour., vol. xxxix., p. 255.

^{page 149 note †} Note to Mr Middleton's paper, Quart. Jour. Geol. Soc., vol. i., p. 216.

^{page 152 note *} Lehrbuch der Chemie, vol. ii., p. 607.

^{page 152 note †} Bulletin des Sciences Médicales, vol. xvii., 425. From Jahrbuch der Chemie und Physik, xxii. 458.

^{page 153 note *} Bulletin des Sciences Medicales, vol. xvii. p. 425. From Zeitschrift für Physik und Mathematik.

^{page 154 note *} Chemical Society's Memoirs, vol. ii., p. 101.

^{page 154 note †} Poggendorf's Annalen, vol. i., p. 80.

^{page 154 note ‡} Brewster's Journal of Science.

^{page 154 note ∥} Chemical Society's Memoirs, vol. ii., p. 247.

^{page 155 note *} As the fact of the frequent presence of fluorine in water must hereafter enter as an important element into all speculations as to the cause of the corroding action of water on glass, I place here on record the result of an accurate quantitative trial on the latter subject.

I am indebted to Mr John Adie for the particulars of the following experiment, which was made with a view to discover what peculiarity in the structure of glass unfits much of it for optical purposes. A cube of glass, two and a half inches square, was inclosed in a fir box, and fixed immovably in it by pieces of wood. Holes were pierced in the sides of the wooden case, so as to permit the free passage of the water, and the whole was placed in an engine-boiler, supplied with the Edinburgh pipe-water, and left here for six months. During that period the boiler was in action twelve hours each day; the water being under a pressure of 35 pounds on the square inch, and at a temperature of about 260° Fahr. The cube weighed, when first immersed, 9157 grains, and, when taken out, had lost 457 grs., or about part of its weight. It is right to mention, that the condensed steam was returned to the boiler, so that fresh saline matter was only furnished in the water added, from time to time, to supply the waste.

^{page 155 note †} London Phil. Mag., No. 144, p. 14.

^{page 155 note ‡} On the Chemical Composition of Calcareous Corals, by B. Silliman junior.—American Journal of Science, vol. i. Second Series.

^{page 156 note *} Transactions of the Royal Polytechnic Society of Cornwall, quoted in Edin. Phil. Journal, vol. xl., p. 115.

^{page 157 note *} Griffin's Rosé's Quantitative Chemistry, p. 348.

^{page 158 note *} Chemical Society's Memoirs, vol. ii., p. 103.

^{page 158 note †} Ibid.

^{page 158 note ‡} Ibid, p. 182.

^{page 159 note *} Chemical Society's Memoirs, vol. ii. p. 182.

^{page 159 note †} Ann. de Ch., t. lv.

^{page 159 note ‡} Simon's Animal Chemistry, vol. ii.

^{page 161 note *} These speculations will be found noticed in Berzelius' Traité de Chimie, or in Simon's Animal Chemistry, vol. ii., art. Gastric Juice.

^{page 162 note *} Certain of the recent observers have endeavoured to reconcile the conflicting statements of their predecessors in reference to this subject, but with little success. Dr Daubeny conceives that the failures may have arisen, in part, from the bones examined not having been deprived of their gelatine before being tested for fluorine, so that the animal matter prevented the hydrofluoric acid from acting on the glass.* But on the one hand, Fourcroy and Vauquelin, who were unsuccessful searchers for the element in question, pointed out long ago the necessity of burning away the gelatine as a preliminary step, and always did so before looking for fluorine.† On the other hand, Mr Middleton, who found that substance abundantly in bones, simply broke the latter into small fragments, and heated them with concentrated sulphuric acid. He states, moreover, that the time occupied by each experiment was only between five and ten minutes.‡ Dr Daubeny refers likewise to the presence of salts of volatile acids and salt radicals, such as chlorides and carbonates, from which hydrochloric and carbonic acids are evolved when sulphuric acid is poured on the bones, and which sweep away the hydrofluoric acid before it has time to corrode the glass. He has accordingly described a method of procedure which gets rid of the volatile bodies in question, but only at the risk of losing, in the liberal washings prescribed, much of the fluoride of calcium. It cannot be doubted that the acids which accompany the hydrofluoric, when sulphuric acid is poured upon burned bones, dilute and carry away the body sought for. But Fourcroy and Vauquelin's experiments, which were made by distilling bones with sulphuric acid in glass vessels, could have been but little affected by this source of fallacy; and Berzelius' successful results were obtained in the very same way.

After trying Daubeny's process several times, I am constrained to acknowledge that I did not find it give any better results than the simpler one previously in use. If it be deemed requisite to get rid of the carbonic acid of bones before testing for fluorine, I believe it could be done most efficaciously by digesting them, after being burned and reduced to powder, in a solution of tartaric acid, and, after the whole carbonic acid had been expelled, drying up the mass.

Rees, taking the opposite view from Daubeny, has endeavoured to prove that, where fluorine has been supposed to be present, it was in reality phosphoric acid that corroded the glass.§ He acknowledges, however, that this explanation applies only to those cases where the bones were distilled with sulphuric acid, and the product of distillation evaporated to dryness in glass vessels. He regards as unexceptionable, experiments made with platina crucibles covered with waxed glass; and as Middleton's, Daubeny's, and my own trials were made in this way, and distinct corrosion or etching obtained, his suggestion must be considered as leaving the subject where it found it.

^{page 162 note *} Chemical Society's Memoirs, vol. ii., p. 100.

^{page 162 note ‡} Memoirs of Chemical Society, vol. ii., p. 135.

^{page 162 note †} Annales de Chimie, tome lvii., p. 38.

^{page 162 note §} Edin. Phil. Journal, vol. xxviii., p. 93.