70 Imperial Institute of France. 



and he attains this remarkable result : viz. that all the in- 

 soluble salts are decomposed by the above two carbonates j 

 but that the mutual change of their principles cannot be 

 completely effected in any case ; and reciprocally, that all 

 the soluble salts from which the acid may form an inso- 

 luble salt with the base of the insoluble carbonates, are de- 

 composed by the latter, until the decomposition has at- 

 tained a certain limit, which cannot be exceeded ; so that, 

 in identical circumstances, combinations are produced ab- 

 solutely opposite in their natures. M. Dulong observes, 

 that there is perhaps no fact more evidently contradictory 

 to Bergman's theory of affinities. He founds the explana- 

 tion which he gives of these })hEEnomena, in appearance 

 contradictorv, upon the changes which take place during 

 decomposition; in the degree of saturation of the alkali, 

 which is always in excess, and forms a new application 

 of the principle so well established by M. Berthollet, 

 upon the influence of the mass in chemical phaenomena. 

 Finally, he deduces from this theory a method of foreseeing 

 what are the soluble salts susceptible of decomposing any 

 given insoluble salt. 



The celebrated Scheele discovered in 1780, that Prussian 

 blue is only a combination of iron with a particular acid 

 which the chemists have since called Pniss'iaii acid. Ft had 

 not hitherto been obtained mixed with abundance of water. 

 M. Gav Lussac in decomposing the prussiate of mercury 

 with the nmriaiic acid by the aid of heat, by rectifying the 

 product in flasks immersed in ice, and by rectifying it over 

 carbonate and muriate of lime, succeeded in giving to the 

 prussic acid the highest degree of concentration. In this 

 state, this acid possesses remarkable properties. Its smell 

 is almost insupportable; and, what is more singular, it boils 

 at a heat of 26 degrees and freezes at 15 ; an interval so 

 inconsiderable, that when we place a drop upon a sheet of 

 paper, the evaporation of part produces a sufficiency of 

 gold to freeze the remainder. 



M. Boullay, a chemist residing at Paris, to whom we are 

 indebted for the discovery of a phosphoric ether, has also 

 Ibrmed one w'th alcohol and arsenic acid: but for this 

 purpose abundance of these sul;stances must be employed. 

 The properties of this ether are similar to those of sulphuric 

 or common ether, and the theory of its formation is the same. 

 M. Chretien, a physician of jMontpelier, having dis- 

 covered in certain preparations of gold, some very remark- 

 able properties in the cure of syphdilic and lymptiatic ilxa- 

 capcs, the attention of chcmisia has been directed to this 



metal. 



