234 ) Mr. Chevenix’s Analysis of 
a part of their oxygen, one to the other, in favour of some 
particular solvent. When the metallic oxide A , for instance, 
containing 25 per cent, of oxygen, is in contact with the metal- 
lie oxide B , containing 10 per cent, they will each remain qui- 
escent in their respective states. But, if the solvent C comes to 
be added, and if the substance B, at 10 per 1 cent, of oxygen, 
has no affinity for C, but at 15 or 20 per cent, has a very pow- 
erful affinity for it, then may the oxide A lend a part of its 
oxygen, in order to favour the combination of B, at 15 or 20 per 
cent, with the solvent C. Indeed, as soon as I saw the phosphoric 
acid assume gradually a blue tinge, and the undissolved pow- 
der begin to wear a more brilliant appearance, I imagined I 
should not fail to recognize the same fact in this case. When 
phosphoric acid has remained long enough upon the pulverized 
ore to dissolve all it can, the oxygen is concentrated, as it were, 
to the amount of 20 per cent, in the part which is dissolved; 
and all that which could not be dissolved has (through the two- 
fold affinity of copper for oxygen, to the amount of 20 per cent, 
and of phosphoric acid for that oxide of copper, at that degree 
of oxidation,) yielded up its entire share of oxygen, to favour 
the combinations which take place in a new order, the only one 
which can exist among the substances now present. It is, there- 
fore, to the disposing affinity,* caused by the presence of the 
phosphoric acid, which seeks to combine with black oxide of 
copper, that the reduction of 42 per cent, of this ore is entirely 
• As the term predisposing affinity has been objected to, I have used the term dis- 
posing, which I trust will not bethought improper. When in two bodies which, while 
together, remain in their original state, the equilibrium of their principles comes to 
be broken by the presence of a third, we cannot but allow, that it is this third which 
has disposed them to the rupture of that equilibrium; and, most certainly, be the fact 
explained as it may, whatever disposes may be called disposing. 
