Sometimes, when using potash, M. Gautier has mixed nitre with it, and has always obtained a richer product than when potash alone had been employed.—_Jour. de Phar._ 1827, p. 11. 19. _Sulphocyanide of Potassium in Saliva_.—MM. Tiedemann and Gmelin have observed the existence of this peculiar compound in saliva, in two cases; the one when the fluid was secreted during smoking, and the other when no such stimulus was applied.—_Ann. de Chimie_, xxxv. 266. 20. _Decomposition of Sulphate of Copper by Tartaric Acid_.—M. [p209] Planche has observed, that when sulphate of copper is dissolved in wine vinegar, for the purpose of preparing a corrosive liquid to be applied to corns on the feet, that the tartaric acid present in the vinegar displaces the sulphuric acid from a part of the salt, and an insoluble acid tartrate of copper is produced. 21. _Separation of Arsenic from Nickel or Cobalt_.—The following process by M. Woehler seems among the best of those intended for freeing nickel or cobalt from arsenic in the dry way. It is founded upon the circumstances that many alloys, when heated with sulphuret of potash, become changed into a mixture of sulphurets, and that sulphuret of arsenic is very soluble in sulphuret of potash. One part of kupfernickle, fused and reduced to fine powder, is to be mixed with 3 parts of carbonate of potash, and 3 parts of sulphur, in a covered Hessian crucible. The heat is to be gradually raised to redness, and until the mass is just entering into fusion, and by no means so highly as to fuse the sulphuret of nickel which is formed. When cold, water is to be added, which will dissolve the sulphuret of potash, and leave a yellow crystalline powder, which is sulphuret of nickel, retaining, perhaps, a little copper or cobalt, but no arsenic, if the operation has been well performed. When, however, the object is to have the nickel perfectly pure, it should be fused a second time with sulphur and potash. The method of freeing cobalt from arsenic, is the same as for nickel; but it is then necessary to perform the operation a second time. The cobalt (that of Tunaberg) has never been perfectly freed from arsenic by one operation, but has never retained any after the second.—_Archiv für Bergbau_, 1826, p. 186. 22. _Compounds of Gold_.—According to late experiments of Dr. Thomson, peroxide of gold consists of 1 atom gold 25 3 " oxygen 3 --- 28 and is consequently a teroxide. Muriate of gold consists of 2 atoms muriatic acid 9.25 1 " per oxide of gold 28. 5 " water 5.625 ------ 42.875 _Edin. Journal_, p. 182.