254 Dr. Hare on the Chemical Nomenclature of Berzelius. 
question cannot combine with any base, either directly or indi- 
rectly, that consequently it does not give salts, and that salifiable 
bases decompose it always into nitrous acid and nitric oxide gas. 
It is not then a distinct acid, and as such ought not to be admit- 
ted into the nomenclature.’ ” 
I suggested a definition here subjoined, which is founded up- 
on your own electro-chemical classification, and which is no 
more than an enunciation of a rule acted upon, and consequently 
sanctioned tacitly by yourself and all other chemists. The de- 
finition in its amended form, as given in my text-book, is as 
follows :— 
““ When of two substances capable of combining together to form 
a tertium quid, and having an ingredient common to both, one 
prefers the positive, the other the negative pole of the voltaic series, 
we must deem the former an acid, the latter a base; also, any 
body capable of saturating an acid, as above defined, is a base, 
and any body capable of saturating a base, as above defined, is 
an acid.” 
It follows that agreeably to the nomenclature proposed by Far- 
aday, every acid is an ‘‘anion,’’ every base a ‘‘cathion.” 
But to proceed to another part of the letter, which I have had 
the honor to receive from you, it is there alleged that although 
“ nitrate calcique’’ (nitrate of lime) is a deliquescent salt, while 
fluor spar is a stone, you class them together because they have, 
in common, the property of yielding with sulphuric acid gypsum 
and a free acid. But allow me respectfully to inquire how, con- 
sistently with your system, sulphuric acid can extricate a free 
acid from fluoride of calcium? By your own premises fluoride 
of calcium is a salt, then wherefore is not the fluoride of hydro- 
genasalt? If it be a salt, where is the analogy between the 
reaction of the sulphuric acid with the nitrate of lime and the 
fluor? In the former case sulphuric acid liberates an acid by a 
superior affinity for a base already existing ; in the latter case, by 
causing the oxygen of its combined water to unite with calcium, 
it generates a base and afterwards combines with it; and, while 
decomposing one fluoride, gives rise to another. In the instance 
of the nitrate, one amphide salt is replaced by another amphide 
salt, while an acid is liberated; in the instance of the fluoride, an 
-haloid salt is replaced, both by an ampbide salt and another haloid 
compound, As, according to your system, this compound con- 
