xliv Historical Sketch of the Physical Sciences, 1818. 
vii. 314.) I have often practised this method since Gay-Lussac 
pointed it out and have found it to answer very well. 
4. Hydrosulphurous Acid.—I have given this name to a pecu- 
liar compound formed wherever three volumes of sulphuretted 
hydrogen gas, and two volumes of sulphurous acid gas, both 
dry, are mixed together over mercury ; these two gases condense 
each other when mixed in the above proportions. The com- 
pound formed is a solid substance, which has an orange yellow 
colour. Its taste is at first acid, but becomes at last hot, and 
continues in the mouth for some time. It gives a red colour to 
vegetable blues, provided the least moisture be applied at the 
same time. Itis decomposed by liquids, and does not combine 
with the salifiable bases while dry. It does not precipitate 
barytes water, except when boiled in it for some time. It re- 
quires a higher temperature for fusion than common sulphur ; 
but it is converted into that substance if it be kept in fusion for 
some time.—(See Annals of Philosophy, xii. 441.) 
5. Acids of Tungsten and Uranium.—Chevreul has shown 
that the peroxides of these two metals have the property of 
reddening litmus paper, and has therefore concluded that they 
ought to be ranked among the acids.—(See Annals of Philo- 
sophy, xii. 144.) I may remark that the acid nature of these 
bodies had been already demonstrated by much more decisive 
qualities than the reddening of litmus paper. Tungstic acid 
combines with the acidifiable bases, and forms neutral salts, 
some of which are crystallizable. The peroxide of uranium 
unites with potash, and neutralizes it. It has been found native 
united to lime, and in all probability has the property of neu- 
tralizing all the salifiable bases and of forming salts with them. 
Uranium then agrees with manganese in being capable of form- 
ing an alkaline body with one proportion of oxygen, and an acid 
body with another proportion; for nothing can be more com- 
pletely entitled to the appellation of a salt than the compounds 
which the protoxide of uranium forms with sulphuric and nitric 
acids. 
6. Sulpho-chyazic Acid.—Two valuable experimental papers 
have appeared upon this interesting acid, one by Theodore von 
Grotthuss, the other by Vogel. A translation of both has ap- 
peared in the Annals of Philosophy, xii. 39, 89,101. I have 
verified M. Vogel’s formula for preparing this acid. It is merely 
an improvement of the method invented by Theodore von Grot- 
thuss. In my trials 1 found it to answer extremely well. Being 
a much shorter and easier method than that contrived by Por- 
rett ; it will no doubt be employed by chemists to enable them 
to procure this curious, though hitherto much-neglected acid. 
The modified process of Grotthuss is as follows : 
Mix together equal quantities of prussiate of potash and flowers 
of sulphur; put the mixture into a matrass, expose it to a heat 
sufficient to fuse it, and keep it in a state of fusion for an hour 
9 . 
