3^5 Jxefcarcles rcfpcBtng 



nitric, and muriatic acids ; fo that the a6lion of the two firft, 

 which diminifhes in proportion as the oxidation advances, is 

 fometimes fo much weakened, that they abandon entirely, or 

 are incapable of diflfolving fome very oxided metals: on the 

 contrary, the muriatic acid diffolves them and holds them in 

 folution, fo that it cannot be perceived whether its acYion be 

 weakened, or whether, on the contrary, it be not increafed 

 by a gi eater oxidation. A probable explanation may be 

 given of this. Sulphur and azote, the bales of the two for- 

 mer, are fa tu rated with oxygen, fo that their refulting affinity 

 for the fubttances that are alio greatly oxygenated is very 

 weak ; but the muriatic acid, which appears to have in its 

 conftituiion only a very fmall portion of oxygen, ought to 

 ha.e a much greater difpotition to combine with oxygenated 

 fubitailces. 



7. Tn the foregoing observations I have fuppofed that the 

 different alkalis mare the acid of a metallic folution with the 

 oxide which is precipitated. I fpeak not of precipitates by 

 ammonia, which in fome circumflances is decomposed, and 

 by that means changes the confiitution of the precipitate, as 

 has been particularly (hown by Fourcroy 3 but this property 

 is fubjeit to modification* which demand particular attention. 

 Baven's experiments have appertained that the precipitates 

 of mercurial nitrates and muriates retain a greater or lefs 

 portion of acid, fo that, on expound the precipitates, of the 

 mercurial nitrate to a fufficient heat, fome nitrous acid is 

 difengaged ; and on making the fame experiment on the pre- 

 cipitates of mercurial muriate, a greater or lefs quantity of 

 infoluble mercurial muriate is fublimed. I mall here add 

 fome observations to thofe I have already made. (Art. XII I, 

 No. «.) 



When oxygenated muriate of mercury is decompofed by 

 the precife quantity of carbonate of foda neeeffary to effect: 

 its prceipi 1 ation, the precipitate contains muriatic acid, car- 

 bonic acid, and oxide of mercury, in excefs ; fo that on ex- 

 poling the precipitate to the action of heat, carbonic acid gas 

 and oxxgen gas are difengaged; nearly half the mercury is 

 reduced to metal, and the reft of the precipitate is fublimed, 

 retaining all the muriatic acid which remained in combina- 

 tion with the oxide, and forming the mercurial muriate ob- 

 ferved by Bayen. The liquid over the precipitate affords by 

 evaporation, at firll carbonate of foda, and afterwards a triple 

 fait in which foda predominated. 



Carbonate of potafh presents different phenomena. A 

 fmall portion only is required to produce a total precipitation 

 in the folution of co.rronve mercurial muriate, and the preci- 

 pitate 



