54 Mr. kirwan’s Experiments and Obfercations on 
decompofition, the precipitating metal yielding its phlogifton to 
the precipitated metal, while the precipitated metal yields its 
acid to the precipitant . Nor has this efcaped the fagacity of 
Mr. bergman, 2 N. Aft. Upf. 205. who has even confirmed 
it by experiments which I have repeated, and found exaft. 
Thus, though copper, in its metallic form, precipitates filver 
and mercury from the nitrous acid with great eafe, yet the calx 
of copper will precipitate neither. The fuperior affinity of 
acids to metallic earths, in preference to alkalies and unmetallic 
earths, requiring further proof, I (hall here demonflrate it in a 
few inftances, with regard even to tliofe metals which are com- 
monly thought to have the leaf: affinity to acids. And, firft, 
that the nitrous acid has a ftronger affinity to filver than to fixed 
alkalies, appears by a curious experiment of Mr. monnet’s 
(Diflolution des Metaux, p. 159.). If a folution of filver in 
nitrous acid be poured into a mixed folution of fixed alkali and 
common fait, the lilver will be precipitated by the marine acid 
of the common fait, and not by the free alkali contained in the 
liquor, for a lima cornua is found. Now if the nitrous acid had 
a greater affinity to the free alkali than to the filver, it is evi- 
dent, that the decompofition would be wrought by the free 
alkali, and then the filver would be precipitated pure, and not 
in the flate of horn filver; but as it is precipitated in the ftate 
of horn filver, it is plain, its precipitation was not effected by a 
fingle but by a double affinity. From whence it alfo follows, 
that the marine acid has a greater affinity to filver than the 
nitrous has to fixed alkalies. I repeated this experiment with a 
folution of lead and alfo of mercury in the nitrous acid, and 
the refult was fimilar, horn lead and marine fait of mercury 
ibeing formed. 
With 
