of Phosphorus and Sulphur , &c. 413 
at mean temperature and pressure, and 100 cubical inches of 
sulphuretted hydrogene 36.5 grains, and the last result agrees 
very nearly with one given by MM. Gay Lussac and The- 
nard, and one gained by my brother Mr. John Davy. 
If 34, the weight of 100 cubical inches of oxygene gas, be 
subtracted from 68, it will appear that sulphureous acid con- 
sists of equal weights of sulphur and oxygene, an estimation 
which agrees very nearly with one given by M. Berzelius; 
and if 2.27, the weight of 100 cubical inches of hydrogene be 
subtracted from 36.5, the remainder 34.23 will be the quan- 
tity of sulphur in the gas ; and the number representing sul- 
phur may be stated as 30 ; and sulphureous acid as composed 
of one proportion of sulphur 30, and two of oxygene 30; and 
sulphuretted hydrogene as composed of one proportion of sul- 
phur, and two of hydrogene. 
From the experiments of MM. Gay Lussac, it appears that 
sulphuric acid decomposed by heat affords one volume of oxy- 
gene to two of sulphureous acid: from this it would appear to be 
composed of one proportion of sulphur to three of oxygene. I 
have endeavoured, in several trials by common heat and by 
electricity, to combine sulphureous acid gas with oxygene, so as 
to form a sulphuric acid free from water, but without success; and 
it is probable, that three proportions of oxygene cannot be com- 
bined with one proportion of sulphur, except by the intermedium 
of water. Mr. Dalton has supposed, that there is a solid sul- 
phuric acid formed by the action of sulphureous acid gas upon 
nitrous acid gas. But I find, that when dried sulphureous 
acid gas and nitrous acid gas are mixed together, there is no 
action ; but by introducing the vapour of water, they form 
together a solid crystalline hydrat ; which when thrown into 
MDCCCXII. - 3 H 
