1818.] on Sulphuretted Hydrogen Gas. 443 



pletely condensed ; and lose their gaseous state entirely, when we 

 mix three volumes of sulphuretted hydrogen gas with two 

 volumes of sulphurous acid gas. Two volumes of the former, 

 when mixed with one of the latter gas, did not undergo complete 

 condensation. The substance formed was quite dry ; and I could 

 not separate any moisture from it by the application of heat, or 

 by any other method which I could think of. Hence we have 

 no experimental proof of the formation of water ; nor is theory 

 more favourable to the notion. Let us substitute, as before, atom 

 for volume, that we may judge of the elements which have acted 

 on each other. 



Atoms. Atoms. 



3 atoms of sulph. hydrogen contain. . . 3 sulphur + 3 hydrogen 

 2 atoms sulphurous acid contain 2 sulphur + 4 oxygen 



So that there are present three atoms of hydrogen and four atoms 

 of oxygen. Were these bodies to unite and form water, it is 

 obvious that there would remain one atom of oxygen gas uncom- 

 bined, which would amount in bulk to the fourth part of the 

 sulphurous acid gas, or half a volume. In my experiment I 

 mixed over mercury 12 cubic inches of sulphuretted hydrogen 

 with eight cubic inches of oxygen gas. If Thenard's statement 

 were accurate, namely, that water is formed during the action 

 of these two gases on each other, the residual oxygen gas would 

 have amounted to two cubic inches ; whei'eas there was no 

 residue, except an insignificant bubble of common air not larger 

 than a pea. 



I think after the preceding detail there cannot be a doubt 

 that the hypothesis of Thenard, that, when these two gases are 

 mixed, they are converted into water and sulphur, is inaccurate. 

 In reality, the two gases unite together and form a compound, 

 which has hitherto been mistaken for sulphur, though it 

 possesses properties somewhat different from that combustible 

 substance. 



Its colour is orange-yellow, without any mixture of the green- 

 ish tinge which distinguishes sulphur. It is not tasteless, like 

 sulphur, but gives a sensibly acid impression to the tongue : this 

 impression becomes at last hot, or peppery, and continues in 

 the mouth for a considerable time. When the dry compound is 

 applied to paper stained blue with litmus, it does not produce 

 any sensible change on it ; but if we moisten the paper ever so 

 little, it is immediately rendered red by it. Hence I conceive 

 that this compound possesses acid properties. But it is an acid 

 that cannot be applied to any useful purpose in chemistry, as it is 

 decomposed by all liquid bodies that I have tried ; namely, 

 water, alcohol, nitric acid, sulphuric acid ; and as it does not 

 sensibly unite with the salifiable bases when presented in a dry 

 state. The acid which gives the red tinge to vegetable blues is 

 neither the sulphuric nor sulphurous ; for when the compound is 



