324 Mefearcbes rrfpefiing 



be 'taken up by the concentrated nitric acid, without giving 

 out much nitrous gas. From the I'olution prepared hv heat, 

 a precipitate is obtained rather of a yellow colour, which is 

 not foluble in muriatic, but readily diffolves in nitric acid, 

 giving out a little nitrous gafi. The fupernatant fluid affords 

 by evaporation a little corrofive mercurial muriate. 



If this experiment be made with a nitrate fo prepared that 

 the mercury fhalJ be in the mod oxided flate, and which has 

 not rediifolved any metallic mercury, and if it be diluted with, 

 a considerably large quantity of water, no precipitate is formed, 

 but all the mercury is fouikl in the (Late of corrolive mercu- 

 rial muriate : it is obtained in this ftate, however, only but 

 in a final I quantity, and fomelimes even none is had, accord- 

 ing to the proportion of muriate of foda employed, becaule 

 the- corrofive mercurial muriate has the property of forming 

 with the nitrate of foda a quadruple fait. This fait i9 capable 

 of forming rhomboidal cryftals, grooved on their face, of a 

 coniiderable iize : it fufes upon red-hot coals ; by expofing it 

 to a fufficient heat in a retort, all the mercury is feparated in 

 the form of corrofive mercurial muriate. The refidue is a 

 nitrate of foda which retains a little muriatic acid, fo that 

 the feparation which takes place is decided by the refpedtive 

 volatility of the fubftances, and by a difference of affinity be- 

 tween the nitric acid and the muriatic acid for the oxide o£ 

 mercury. After the cry utilization of this fait, another is ob- 

 tained in fmall needles, which appear to be a complex fait, 

 in which the oxide of mercury is found in a greater propor- 

 tion. 



Nothing certain can be determined as to the refults of the 

 mixture of the nitrate of mercury highly oxided, and the mu- 

 riate of foda, becaufe they vary according to the proportions 

 of the fubftances which act, 



I deduce from the preceding observations, that the nitric 

 folution of mercury may hold this metal in i'olution from the 

 loweft degree of oxidation to the higheft, or -to that which 

 is required for the constitution of corrofive mercurial muriate; 

 that it may poflefs it in all the intermediate degrees, but that 

 its properties will be different according to the degree of 

 oxidation. 



5. Fourcroy lays it down as a principle, that any metallic 

 oxide whatever gives to acids a colour (imilar to that which 

 it has itfelf; whence he concludes, that when a mercurial 

 precipitate which proceeds from a white fait acquires another 

 colour, a change mufl have been made in the oxidation. 

 This opinion does not appear to me to be well founded. I 

 took fome muriatic acid and diifolved in it fome red oxide of 



mercury ; 



