* 



'204 ANNUAL OF SCIENTIFIC DISCOVERY. 



as possible. Anthracite suffers the least; bituminous the most. 

 According 1 to the experiments of Grunclmann, in Germany, coal 

 exposed to the weather in heaps lost during a period of nine 

 months 50 per cent, of its value as fuel, and about as much as a 

 gas-making material ; it undergoes a process of slow combustion, 

 taking up oxygen, and giving off the volatile products of oxida- 

 tion, air and moisture playing the principal part, and warmth pro- 

 moting it ; the valuable combustible ingredients are lost, and the in- 

 jurious ones, as sulphur, oxygen, and ash, are relatively increased. 

 Coke from weathered coal is of inferior quality, losing its coher- 

 ence. 



EXTRACTION OF POTASH FROM FELSPAR. 



M. Daubree placed felspar and distilled water together in a 

 cylindrical vessel, which he made to rotate rapidly on its axis. 

 Under this movement he found that the felspar underwent decom- 

 position ; the water became alkaline, and he was enabled to sep- 

 arate considerable quantities of potash or soda, according to the 

 rock operated on. The supply of potash becomes a more impor- 

 tant question every year, as the vegetable sources of this sub- 

 stance are gradually disappearing; in the felspathic rocks there is 

 an inexhaustible supply, but hitherto it has not been possible to 

 extract it profitably. If M. Daubree's process can be made to an- 

 swer on the large scale, an important industrial problem is solved. 

 He remarks that this fact may throw some light on the changes 

 which are taking place on the surface of the earth. For instance, 

 he asks, what may be the effect of the constant movement of the 

 sea dashing against the rocks? Probably not merely disintegra- 

 tion but decomposition must be produced. Comptes Bendus, 

 Feb. 25, 1867. 



PREPARATION OF OXYGEN. 



M. Mallet has published in the " Comptes Rendus," Feb., 1867, 

 the following cheap and easy mode of preparing oxygen on 

 the large scale. Cuprous chloride absorbing oxygen from the 

 air to become converted into the oxychloride, which o*xygen is 

 driven off on the application of heat, he mixes the cuprous chlo- 

 ride with sand or kaolin, and places it with a little water in a hori- 

 zontal iron retort, where it is agitated while a current of air is 

 made to pass. The formation of the oxychloride is completed in 

 an hour or two, when heat is applied, and the oxygen collected. 

 The oxychloride may afterward be revived by the same process. 

 A kilogramme of the cuprous chloride is said with each operation 

 to yield 28 to 30 litres of oxygen ; the loss of material is very 

 slight, 100 grammes of the chloride losing only 9 grammes in the 

 repeated revivifications necessary to furnish 36 litres of gas. 



Another process is given by Winkler. Binoxide of manganese, 

 heated with sulphuric acid, yields oxygen; but the sulphate of 

 manganese produced forms a hard cake liable to break the retort. 

 He uses bisulphate of soda in the place of sulphuric acid, three 

 parts of the dry bisulphate being mixed with one of manganese ; 



