On ISlerctirial Salts i 3/3 



all the parts may be carefully defcribed, and that thefe parts 

 may be affigned to the regions which they compofe. Such, 

 it appears is the idea which may be formed of the prefent 

 Itate of the chemical knowledge of falts. Their general for- 

 mation feems to be well known, the great divifions are v.'ell 

 eltabliflied, and the principiJ facils have been exactly obferv- 

 ed and clalled j bat notwilhfianding thefe fatisfattory labours, 

 many details are ftill unknown or imperfect. Hence the 

 refcarches of the chemifiis of the inflitute during this quarter 

 have been particularly directed towards this objcft, and it 

 will be feen that they have not been fruillefs. 



The liquor charged with the colouring matter of Pruffian 

 blue, having manifefted the property of takinc: metals from 

 their folvents, without producing a decompofition of thefalts 

 with an alkaline or earthy bafe, the phcenomenon of the pre- 

 cipitation of barytes had been confidered as art indication 

 of the metallic nature of that fubdance, which could not be 

 reduced to a metallic Hate, bccaufe it had a greater affinity 

 for oxygen than carbon. The moft celebrated chemifts had 

 adopted this Oj)inion, others had announced that precipita- 

 tion did not lake place. Mr. William Henry thus main- 

 taining that prufliales perfectly purified did not produce any 

 precipitation, confirmed himfelf the firit obfervations of 

 iiergman and Lavoifier, and announced that there was formed 

 by double affinity a real prufliate of barytes. C. Guyton, 

 having long oblerved that pruffiate of lime was decompofed 

 by carbonate of potafli, made ufe of this experiment, and 

 thofeof Mr. Henrv, to fix the theory of thefe phneiiomena; 

 and, inftead of concluding, like the Englifh chemill, that ba- 

 rytes differs in this refpc6l from other earths, and approaches 

 the nature of metals, he (hows that the fame etl'etl: takes 

 place with lime, ftrontian, magnefia, potafli, foda, and 

 even ammonia, and confequently that, in all thefe cafesj 

 there is nothing but the neccflary refult of the concurrence of 

 fcvcral divellenT forces. 



On Mercurial Salts. 



After treating different oxides of mercury, as already rnch- 

 tioned in his nunioir, C Fourcroy continued to read an ac- 

 count of his hibour durina; the lad quarter. In this fecond 

 part he employed himlelf on the fulphatcs and nitrated of 

 mercury ; a very complex kind of compounds, exceedingly 

 variable, the cliararters and properties of which have been 

 cKamincd by many chemills, witliout their being able to de- 

 termine iho real diifercnces between them, and i)ar(icularly 

 the caufe of ihcfe dilfcrcnceg. The author had already made 



VoL.XlV. No. .55. S this 



