210 Sir Humphry Davy’s experiments on a solid 
its crystalline form. There is every reason to believe, that 
the proportions of its elements are definite. In one expe- 
riment I found, that a small quantity of the new compound 
in being converted into the rhomboidal crystals, gained rather 
less than half its original weight from the addition of the add, 
i. e. 2 grains became 2.8 grains. 
In experiments in which the products of the decomposition 
of the compounds from phosphoric and sulphuric acids were 
collected, the acids disengaged were found in their state of 
hydrates, from which it is probable, that the crystalline 
compounds are hydrates, and that the common acids carry 
their definite proportion of water into the combination. It is 
not indeed unlikely, that the presence of water is connected 
with the phenomenon of combination, and there is an instance 
of this kind which I long ago pointed out. Sulphurous acid 
gas, and nitrous acid gas, appear to have no action on each 
other, unless Water be present ; but with the vapour of water 
they form a solid crystalline hydrate. 
Reasoning from analogy, it is probable, that a compound 
of oxygene may be formed, containing less oxygene than the 
new compound. I have made many experiments with the 
hope of discovering a body of this kind ; but without any 
decided success. When the solution of the new compound 
is made to act on the double compound of iodine and the 
alkaline metals, iodine is produced, which during its sublima- 
tion, yields no gaseous product. Iodine heated in a solution 
of the new compound slightly colours it, but this appears to 
be merely in consequence of its combining with the water ; 
and the iodine rises in vapour with the water without decom- 
posing the compound. In some experiments on the action of 
