138 Proceedings of the 



3. That these opposite qualities of the two compositions afford 

 the means of separating soda and potash when in solution together; 

 the former generating a perchlorate easily soluble in alcohol, and 

 the latter a perchlorate absolutely insoluble in that liquid. 



4. That any acid whatever, which was primitively combined with 

 potash, will always be separated and set at liberty by perchloric acid. 



Production of Perchlorate from Chlorate of Potassa. On the 

 23d of May, M. Serullas communicated the result of his obser- 

 vations on the change of chlorate of potash into oxychlorate (per- 

 chlorate) of the same base, by the action of heat, and on a new 

 method of obtaining oxychloric or perchloric acid. The simila- 

 rity of the phenomena manifested in the production of oxychlo- 

 rate of potash, with those observed in the production of oxychloric 

 acid, led M. Serullas to suppose that the simple action of a high 

 temperature, maintained within certain limits, would convert chlorate 

 into oxychlorate of potash, by combining part of the oxygen with 

 the chlorate remaining undecomposed. He had long since observed 

 that chlorate of potash, decomposed by fire, left a saline residue 

 not easily soluble, and removable with difficulty from the tubes in 

 which the experiment was made, but he concluded that former che- 

 mists, in establishing that this residue consisted only of chlorure, 

 had taken notice of all the effects produced by heat at different 

 periods of the operation ; and, therefore, had not directed his attention 

 to that point until accidentally led to do so in the course of his 

 experiments on oxychloric acid. He observed that when chlorate of 

 potash is heated in a crucible, it first melts, and then boils, at which 

 state there is an escape of oxygen. When the heat is regulated 

 sparingly, after a certain duration of the ebullition, this escape of 

 oxygen ceases, unless the temperature be raised ; if the operation 

 be then suspended, and the solution be filtered while hot, a consi- 

 derable quantity of oxychlorate will be obtained, when it cools, in 

 small brilliant crystals : 40 parts of chlorate furnished 17'5 parts of 

 oxychlorate. M. Serullas has established that Stadion, and all the 

 other chemists, were wrong in supposing that oxychlorate of potash 

 is decomposed at 392 Fahr. : it requires at least 752 Fahr. 



In order to obtain oxychloric acid, oxychlorate of potash must 

 be boiled with silicated hydrofluoric acid, in great part eva- 

 porated, so as to obtain, when cool, a more abundant deposit of 

 the gelatinous fluosilicate of potash ; this must be filtered, again 

 evaporated, left to cool, again filtered, concentrated in a cap- 

 sule, and then distilled in a small retort. In order to precipitate 

 the small quantity of fluosilicate of potash and of oxychlorate, 

 which may exist in the oxychloric acid, it is only necessary to pour 

 into it a little concentrated alcohol, filter it, dilute it with water, 

 and then let it evaporate. The oxychlorate of potash contains 

 65-725 parts in 100 of oxychloric acid. This simple means of pro- 

 curing the acid is highly important, as from M. Serullas' discovery 



