188 On Totdine. [Sepr. 
tity of substance which it is necessary to add to obtain the neutral 
state compared with the whole of the same substance contained in 
the neutral compound. Let us apply these considerations to the 
acids themselves, and to the alkalies. 
Neutrality, or complete saturation of the acid properties by the 
alkaline, takes place both between two simple bodies and two com- 
pound bodies, It isin the first case even that acidity and alkalinity 
show themselves in all their energy. Water and white oxide of 
arsenic are neutral combinations, analogous in this respect to the 
salts: and as it is oxygen which possesses acid properties, hydrogen 
and arsenic ought to possess alkaline ones. When oxygen is com- 
bined with the metal in greater quantity than in white oxide, then 
the compound is acid. In like manner protoxide of azote ought te 
be considered as a neutral compound; but when the oxygen is 
combined with azote in three times or five times as great a propor- 
tion, the acid properties of the oxygen are no longer neutralized by 
the alkaline properties of the azote, and the combination possesses 
acid characters. ‘ 
Since most of the oxides are alkaline, though they contain 
oxygen, the metals whose oxides have that property ought them- 
selves to possess it in a much more considerable degree. It would 
seem from this that oxygen loses or preserves its character in com- 
binations, according to the proportion in which it enters into them. 
Let us examine if these proportions should be constant or variable 
to produce this effect. We shall compare the bodies according to 
their volumes in the elastic state, and not according to their ponder- 
able quantities, which have much less influence on their combina- 
tions. 
Jn water there enter two volumes of hydrogen and one of oxygen. 
Hence, equal volumes considered, oxygen is much more acidifying 
than azote is alkalifying; and that equal volumes of azote and 
hydrogen are alkalifying in the same degree, if we can compare 
exactly the protoxide of azote with water. The oxide of carbon 
appears to me to result from the combination of two volumes of the 
vapour of carbon with one of oxygen gas, and if we might consider 
the protoxide of azote and water as combinations equally neutral, we 
might conclude that the acidifying properties of oxygen gas are 
neutralized by a double proportion of the body with which it com- 
bines, and it would be very remarkable that azote, hydrogen, and 
carbon, possess alkalifying properties in the same degree. 
Tn carbonic acid we may conclude with the greatest probability 
that the oxygen is combined with an equal volume of the vapour of 
carbon, and in sulphurous acid that it is combined with an equal 
volume of the vapour of sulphur. But though in nitrous gas there 
are equal volumes of oxygen and azote, this gas does not possess 
acid properties. But as these three compounds contain the same. 
proportions in volume, and as there is no other difference between 
them except that in sulphuyous and carbonic acids, the condensation 
