Inquiry ifito the Laitri ef Affinity, j go 



remark, that this procefs appears to mc to be the mod fimple, and the leaft expenfive for 

 the preparation of the corrofive mercurial muriate. 



The combination which I had formed contained the red oxide of mercury, with all its 

 oxigen 5 yet it was colourlefs ; with ammonia it would have given a white precipitate, and 

 wiih lime and the alkalis a precipitate more or lefs orange coloured. 



The red oxide of mercury readily diffolves in the nitric acid, without any difengage- 

 ment of oxigen ;. this folution cryftallizes and forms a white fait ; but if there be not a 

 fufficient excefs of acid, it gives with water alone a white precipitate ; with a greater quan- 

 tity of water recently diftilled, a yellow precipitate ; with lime and the fixed alkalis a pre- 

 cipitate of a much deeper yellow colour. 



A coloured oxide may therefore form white falts, and afterwards aflume other coloutSj 

 witliout undergoing any change in its oxidation. 



6. Several chemifts have obferved, that the muriatic acid has a greater difpofition to' 

 combine with very oxided metals, than the nitric and fulphurlc acids. Fourcroy applied 

 this confideration with advantage to explain feveral phsenomena. On this fubjefl he thus 

 exprefles himfelf: (Mem. de T Acad. 1790, page 381.) " Every acid requires quantitie»of 

 oxigen in the metals, in order to combine with them ; the muriatic acid in general does 

 hot combine with thofe metals, unlefs they be much loaded with this principle, or highly 

 oxided : the mercury appears to be more oxided in the corrofive muriate than in the nitrate." 

 I fliall take the liberty to make fome obfervations on the principles laid down by my learned 

 colleague. 



It does not appear to be exa£l to fay, that each acid requires different quantities of 

 oxigen in the metals to combine with them ; the nitric, the fulphuric, and the muriatic 

 acids form combinations with mercury, from the leaft to the moft oxided terms ; and it is 

 the feries which refults in the muriates, which makes the principal difference in all phar- 

 maceutical preparations, from the corrrofive fubllmate to the mercurial panacea: but there 

 is this difference, that the combination of the fulphuric acid and the nitric acid with highly 

 oxided mercury is much weaker, and more eafily decompofed, even by the aftion of water, 

 than that of the muriatic acid, which on the contrary prefents a very permanent conftitu- 

 tion. 



If our attention be direfted to thofe metals which have the property of afTuming large 

 proportions of oxigen, fuch as iron, tin, antimony, &c. we fliall obferve the fame proper- 

 ties with regard to the fulphuric, nitric, and muriatic acids, fo that the a£lion of the two 

 firft, which dlminiflies in proportion as the oxidation advances, is fometimes fo much 

 weakened, that they abandon intirely, or are incapable of dilTolving. fome very oxided 

 metals; on the contrary, the muriatic acid difTolves them and holds them in folution, fo 

 that it cannot be perceived whether its adlion be weakened, or whether on the contrary, it 

 be not increafed by a greater oxidation. 



A plaufible explanation may be given of this comparative property of the fulphuric, ni- 

 tric, and muriatic acids. Sulphur and azote, the bafes of the two former are faturated with' 

 1, . oxlgicni , 



