12. _Peculiar Formation of Nitre_.—The leaves and stems of beet root contain oxalate and malate of potash. Some leaves were tied together and hung up in a warm and slightly-humid place, where there was but little light, to dry. Being examined at the end of several months, they were found penetrated with, and covered by, an immense number of minute crystals of nitre. The oxalic and malic acids had been replaced by nitric acid; but whether from animalized matter naturally in the leaves of the plant, or from the action of the air, or in what manner, is not known.—M. HENRI BRACONNOT, _Ann. de Chimie_, xxxv. 260. 13. _Experiments on Fluoric Acid and Fluates, by_ M. Kuhlman.—These experiments were made with dry sulphuric acid and fluor spar, with the intention of proving that fluor spar is truly a compound of fluorine and calcium, and not of fluoric acid and oxide of calcium. A quantity of anhydrous sulphuric acid was prepared with great care, and collected in a glass tube; the latter was then connected with a platina tube charged with fluor spar, which had previously been calcined in a platina crucible, and a glass tube was connected with the other end of the platina tube for the purpose of conducting and facilitating the collection of the gas evolved over mercury. The fluor spar was heated to redness, and then the temperature of the sulphuric acid raised so as to cause a stream of it in vapour to pass over the fluor spar; but there was not the slightest reaction, the sulphuric acid recondensed in part in the farthest tube, and no trace of fluoric acid was produced. Dry sulphuric acid was then put, in the liquid state, in contact with dry fluor spar, but there was no decomposition, and no portion of the spar was converted [p206] into sulphate of lime. The first experiment was then repeated, with the difference of using hydrated sulphuric acid of specific gravity 1.842, and there was instantly much fluoric acid produced, which acted upon the glass.