1815.] On Iodine. 19} 
if the condensation be nothing, as in nitrous gas, the compound is 
neither acid nor alkaline, though it contain equal volumes of azote 
and oxygen. It seems to result from this that neutrality between 
two bodies may be obtained in different ways, by varying their pro- 
portions or the condensation of their volumes, When the propor- 
tion of oxygen is above half the total volume, there ought for a still 
stronger reason to be acidity, Yet when we compare sulphurous 
with sulphuric acid, nitrous with nitric acid, and phosphorous with 
phosphoric acid, we observe that the acidity is the same for each 
. couple of acids, though they contain different quantities of oxygen. 
I consider it as very probable that the oxygen added to sulphurous 
acid to convert it into sulphuric does not change its volume, and 
that we have always the same number of compound molecules which 
combine with the same number of alkaline molecules. This view 
of the subject will explain the permanency of neutrality in the salts 
whose acid is capable of combining with a new quantity of oxygen, 
and it would make the neutral, acid, or alkaline, character depend 
both on the number of heterogeneous molecules which combine, 
and on their arrangement. It will explain likewise why an oxide 
saturates so much the more of an acid as it contains more oxygen ; 
for it will be sufficient to admit that the number of molecules of the 
oxide increases, on receiving a new quantity of oxygen, in the same 
ratio as the number of acid molecules which it saturated at first has 
augmented.* We shall be able to conceive likewise why two bodies, 
like chlorine and oxygen, which have such decided acid characters, 
form, on combining in the proportion of 1 to 2°5, an acid which 
saturates no more than hydro-chlorie acid, which is composed of 
equal parts of chlorine and hydrogen, though the characters of 
hydrogen be ratber alkaline than acid. We shall be able to con- 
ceive likewise why fat bodies and alcohol saturate acids like alkalies, 
and why the same fat bodies saturate alkalies like acids. Lastly, we 
shall be able to conceive the possibility of forming neutral com- 
pounds with bodies which have the same acid or alkaline character, 
and we will admit without difficulty that the oxide of chlorine or 
euchlorine, though resulting from the combination of two bodies 
strongly acidifying, may notwithstanding be neutral. 
Neutrality, as 1 have already observed, takes place as well between 
two simple bodies of opposite characters, as between an acid and an 
alkali. We may say it takes place better ; for in the metallic oxides, 
for example, the alkalinity which they enjoy is the result of two 
Opposite properties, the alkalifying property of the metal, and the 
acidifying of oxygen, modified both by the combination and by the 
proportions. We have easy methods of recognizing the neutral, 
wt or alkaline, state of some combinations; but as these methods 
not apply to all, 1 shall endeavour to point out a new one. 
* It is very remarkable that in tha acids the saturating property appears to 
depend solely on the radical, while in the oxides, on the contrary, it depends ypon 
the oxygen, which they contain, 
