208 Sir Humphry Davy’s experiments on a solid 
appears to form combinations with all the fluid or solid acids 
to which I have been able to expose it, that it does not de- 
compose. When sulphuric acid is dropped into a concentrated 
solution of it in hot water, a solid substance is precipitated, 
which consists of the acid and the compound ; for on evapo- 
rating the solution by a gentle heat, nothing rises but water. 
On increasing the heat in an experiment of this kind, the solid 
substance formed, fused ; and on cooling the mixture, rhom- 
boidal crystals formed of a pale yellow colour, which were 
very fusible, and which did not change at the heat at which 
the compound of oxygene and iodine decomposes, but sub- 
limed unaltered. When urged by a much stronger heat, it 
partially sublimed, and partially decomposed, affording oxy- 
gene, iodine, and sulphuric acid. 
With hydro-phosphoric acid, the compound presents phe- 
nomena precisely similar, and they form together a solid, yel- 
low, crystalline combination. 
It dissolves in solution of hydro- phosphorous acid, but on 
heating the combination, iodine is immediately produced by a 
decomposition of part of the compound, and the remain- 
ing part unites to the phosphoric acid formed. 
When hydro-nitric acid is poured into a concentrated solu- 
tion of it, white crystals form in plates of a rhomboidal figure, 
and which when dried, partially decompose, and partially 
sublime at a much lower heat than the sulphuric or phos- 
phoric compounds, and afford hydro-nitric acid,^ oxygene, 
and iodine. 
It dissolves in solution of oxalic acid, but by a very gentle 
heat, the oxygene of the compound acts on the inflammable 
bases of the acids, and iodine and carbonic acid are disengaged 
in great quantities. 
