432 Chronicles of Science. | July, 
at present in the condition of undeveloped schemes. Beyond those, 
there is an entire absence of any real improvement in any branch 
of metallurgy to be noticed. 
M. L. Cailletez has an interesting memoir on the “ Dissociation 
des gaz dans les foyers métallurgiques,” in which he confirms the 
results obtained by M. H. St. Claire-Deville by experiments on a 
laboratory scale.* 
IX. PHYSICS. 
Liaut.—F ather Secchi has sent to the Academy of Sciences an 
account of the spectra of some stars, as recently seen by him in a 
new spectrometer by Merz, with a prism by Hofmann, of Paris. A 
drawing of the spectrum of « Orionis accompanied the communica- 
tion. The spectrum of Sirius is described by the learned author as 
resembling that of sulphur. 
A suggestion, which is likely to be of considerable value to 
photographers, has been made by Dr. Angus Smith, F.R.S. The 
cause of the destruction of photographs, apparently by the action of 
time only, is generally considered to be due im reality to the 
presence of a minute quantity of hyposulphite of soda remaiming in 
the paper. Hitherto almost the only plan of getting rid of this 
agent has been long and continuous washing in cold or hot water. 
Dr. Angus Smith has suggested oxidizing the hyposulphite of soda 
into sulphate of soda (which is likely to be harmless), by means of 
dilute peroxide of hydrogen. Peroxide of hydrogen has been little 
known to chemists, and even now it is seldom obtained in its pure 
state. It is, however, to be had in a solution, and in a state 
sufficiently strong for many important purposes in analysis. Oxides, 
such as in the case of manganese, which will not fall till more highly 
oxidized, are with advantage treated by it. The lower oxide may 
remain unobserved in a solution, and in a state of minuteness 
sufficient to keep it in suspension; but at the moment of contact 
with the peroxide of hydrogen it blackens and falls. 
When the peroxide is poured into a solution of hyposulphite of 
soda, the change is not observed, as there is no coloured oxide to be 
formed ; but when a salt of barium is afterwards added, it is found 
that sulphuric acid has taken the place of hyposulphurous. The 
strength of the solution does not require to be great. That which 
is sold contains about nine volumes of available oxygen. If diluted 
a thousand times, a solution is obtained capable of oxidizing hypo- 
sulphites. It appears that all the hyposulphurous acid is instantly 
converted. 
Peroxide of hydrogen is in reality an oxide of water ; when the 
* © Les Mondes,’ April 19, 1866. 
