the L<nvs of Affinity. 30$ 



mercury; the folution was eafily effected, wirhout any difen- 

 gagement either of oxygen gas 5 or oxygenated muriatic acid: 

 it fpontaneouily afforded line cryftals of corrofive mercurial 

 muriate. I may here remark, that this proccfs appears to 

 me to be the moil limple and the lea It. expensive tor the pre- 

 paration of the corrofive mercurial muriate. The combina- 

 tion which I had formed contained the red oxide of mercury 

 with all its oxvgen ; vet it was colourlcfs : with ammonia if 

 would have given a white precipitate, and with lime and the 

 alkalis a precipitate more or left, orange coloured. 



The, red oxide of mercury readily diiTolves in the nitric 

 acid without any difengagement of oxygen : this folution 

 cryi'tallizes and forms a white fait; but if there-be not a fuf- 

 ficient excefs of acid, it gives with water alone a white pre^ 

 cipitate ; with a greater quantity of water recently diitilled, a 

 yellow precipitate; with lime and the fixed alkalis, a preci-pi- 

 late of a much deeper yellow colour. A coloured oxide may 

 therefore form white fahs, and afterwards alfume other co- 

 lours, without undergoing any change in its oxidation. 



6. It is known that the muriatic acid has a greater difpofi- 

 tion to combine with highly oxided metals than the nitric 

 and fulphuric acids. Fourcroy applied this confideratiou 

 with advantage to explain feveral phaenomena. He thus ex- 

 prefi'cs himfelf: (Mem. de V Acad. 1790, p. 381.) " Every 

 acid requires quantities of oxygen in the metals in order to 

 combine with them; the muriatic acid, in general, does not 

 combine with thofe metals, unlefs they be much loaded with 

 this principle, or highly oxided : the mercury appears to be 

 more oxided in the corroftve muriate than in the nitrate." 

 I (hall take the liberty to make fome observations on the 

 principles laid down by my-learned colleague. * 



It does not appear correct, to fay, that each acid requires 

 different quantities of oxygen in the metals to combine with 

 them; the nitric, the fulphuric, and the muriatic acids, form 

 combinations with mercury, from the lead to the moll oxided 

 terms ; and it is the feries which remits in the muriates which 

 makes the principal difference in all pharmaceutical prepara- 

 tions, from the corrofive fublimate to the mercurial panaeea : 

 but there is this difference, that the combination of the ful- 

 phuric acid and the nitric acid with highly oxided mercury 

 •js much weaker, and more eafily decompofed, even by the 

 action of water, than that of the muriatic acid, which pre- 

 fents a very permanent conftitution. If we turn our atten- 

 tion to thofc metals which have the property of afiuming 

 large proportion^ of oxygen, fuch as iron,, tin, antimomv&c. 

 we lhall find the fume properties with regard tQ the fulphuric^ 



X 3 nitric^ 



