THE DUBLIN INTERNATIONAL EXHIBITION. 227 
Mr. Swan — not only accomplished, but worked out with such results that 
the most fastidious cannot cavil. This process is based upon the fact that 
gelatine, containing a small quantity of bichromate of potassium, is ren- 
dered insoluble when submitted to the chemical action of the sun's rays. 
All attempts in this direction had hitherto failed, as no half tones were 
produced. The specimens shown are beautiful in the extreme. The 
liability of photographs to fade has tended more than anything else to 
narrow photography as an industrial art. Messrs. Mawson and Swan 
also show collodion remarkable for extreme sensitiveness, and yet 
having been more than six months iodized. They also show collodion 
for glazing pictures, and also for fixing crayon drawings (a new idea). 
Also a new application of Mr. Wharton Simpson's {t collodio chloride 
of silver" for glass printing. Mr. Simpson's original preparation 
would not do for this purpose, and we believe the preparation shown 
contains nitric acid. 
Messrs. Dubosc and Co. (France, 6) exhibit some solid extracts evi- 
dently prepared with great care. They were found by the Reporter to 
be perfectly soluble, and to give transparent solutions. These extracts 
are made for dyeing purposes, and are said by the exhibitors to be used 
in preference to the woods by many of the Manchester houses. 
In Victoria there are exhibited some gums and essential oils, many 
of them new to British commerce. The peppermint oil, distilled from the 
plant grown in the colonies, is excellent. The oil of amygdalina odorata 
{Eucalyptus amygdalina), from its price, might be used in perfuming 
cheap soaps ; whilst the kino-like gums from Eucalyptus rostrata and 
E. Amygdaina, might be used for medical or tanning purposes. The 
essential oils have been examined, as regards their physical properties, 
by Dr. Gladstone, vide 'Journal of the Chemical Society', Vol. XVII, p. 1. 
In the Italian department we meet some things of great interest. 
The mannite, or sugar of mushrooms, exhibited by Prof, de Luca, 
University of Naples (Italy, 32), is procured from the olive tree ; also 
bicarbonate of potassium and sodium, exhibited by Giuseppe Ciaranfi 
(Italy, 28), and obtained by submitting crude soda and potash to the action 
of the carbonic anhydride evolved from the mineral springs of Cinciano. 
The carbonate of iron shown, as might be imagined, only contained 
about ten per cent, of that substance when examined by the Reporter ; 
but the other products are very good. The legitimate application of 
such carbonic anhydride streams would be to carbonate the liquors in 
making soda ash, and thus to prevent that source of trouble— the for- 
mation of sulphide of sodium by the presence of caustic soda. M. 
Scheurer Kestner expresses the formation of sulphide of sodium in the 
black ash residue by the following series of equations : 
(Ca 2 0)a + (Na 2 C0 3 )a=(Ca 2 C0 3 )a + (Na 3 0)a. 
(Na 2 0)a + (Ca 2 S)a =(Na 2 S)a + (Ca 2 0)b. 
(Ca,0)b + (Na 2 C0 3 )b=(Ca 2 C0 3 )b + (Na 2 0)b. 
(Na 2 0)b + (Ca 2 S)b =(Na 2 S)b + (Ca 2 0)c. 
VOL. VI. 
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