414 Sir H. Davy on some Combinations 
water gives off nitrous gas, and forms a solution of sulphuric 
acid. 
I have referred, in the Philosophical Transactions, to the 
combination of chlorine and sulphur. 1 have been able to form 
no compound of these bodies, which does not deposit sulphur 
by the action of water. When sulphur is saturated with chlo- 
rine, as in Dr. Thomson's sulphuretted liquor, it appears to 
contain, from my experiments, only 67 of chlorine to 30 of 
sulphur. 
4. Some general Observations. 
It is a fact worthy of notice, that phosphoric and sulphuric 
acids should contain the same quantity of oxygene to the same 
quantity of inflammable matter; and yet that the oxygene should 
be combined in them, with such different degrees of affinity. 
Phosphorous acid has a great tendency to unite with oxygene, 
and absorbs it even from water: and sulphureous acid can only 
retain it when water is present. 
The relation of water to the composition of many bodies has 
already occupied the attention of some distinguished chemists, 
and is well worthy of being further studied ; most of the sub- 
stances obtained by precipitation from aqueous solutions are, I 
find, compounds of water. 
Thus zircona, magnesia, silica, wh n precipitated anl dried at 
2 1 2 0 still contain definite proportions ot water. And many of the 
substances which have hetn considered as metallic oxides, that 
I have examined, obtained from solutions, agree in this respect; 
and their colours and other properties are materially influenced 
by this combined water. 
I shall give an instance. The substance which has been called 
the white oxide of manganese is a compound of water and the 
