REPORT ON CHEMISTRY. 
461 
through a solution containing free nitric acid, as well as through 
solutions of some nitrates, ammonia and sulphuric acid are 
formed. If the solution be hot and acid, this proceeds with 
considerable rapidity, as may be seen by adding nitrate of 
barytes to the solution when sulphate forms. The presence of 
the ammonia is beautifully shown by adding protosulphate of 
iron, and evaporating when the beautiful pinkish-coloured 
octohaedrons of sulphate of iron and ammonia are deposited * * * § . 
This observation may be found of use in some cases of analysis 
where the presence of ammonia may retain more or less of a 
metallic oxide in solution (as oxide of copper), which it may be 
desirable to precipitate. 
Hyposulphurous acid. —M. H. Rose f has published a new 
analysis of hyposulphurous acid, in which he confirms the pre¬ 
vious deductions of Gay-Lussac. When solutions of the hypo¬ 
sulphites are poured into the solutions of certain metallic salts, 
as those of silver and mercury, half the sulphur in the hyposul¬ 
phurous acid forms a metallic sulphuret, and is precipitated : 
the other half is changed into sulphuric acid, and remains in 
solution. He found the acid contained in the hyposulphite of 
barytes to consist of 
Two atoms sulphur = 4 \^ 
Two atoms oxygen = 2J ’ 
When the one atom of sulphur falls, the other unites with 
both the atoms of oxygen in the acid and with the atom given 
off by the metallic oxide precipitated in the state of sulphuret; 
with these three atoms it forms one atom of sulphuric acid. The 
hyposulphurous acid agrees, therefore, with the supposed sub- 
sulphurous acid of Dr. Thomson J in containing equal atoms 
of the two constituents; but it differs from it in the remarkable 
circumstance of having an atomic weight twice as great. Dr. 
Thomson states the composition of hyposulphurous acid to be 
two atoms sulphur + one atom oxygen. 
Sulphurous acid gas. —Knezaurek § has given a very useful 
and cheap method of preparing sulphurous acid gas. He in¬ 
troduces powdered charcoal into a retort and pours over it con¬ 
centrated sulphuric acid, until on shaking it the mass appears 
moist. On heating, a constant stream of a mixture of two 
volumes of sulphurous acid and one of carbonic acid gases is 
given off, which continues till the mass becomes dry. This 
* Brewster’s Journal , N.S. vi. p. 65. 
f Poggendorf’s Annalen , tom. xxi. p. 436. 
X Chemistry of Inorganic Bodies , vol. i. p. 266. 
§ Baumgartner’s Zeitschrift, ix. 
