Chemical Sctence. 167 
19. Prussian Blue.—Mr. Badnall, of Leek, has taken out a pa- 
tent for improvements in dyeing with Prussian blue. The improve- 
ment consists in preparing the Prussian blue, by mixing it in fine pow- 
‘der with strong muriatic acid, and stirring it until the whole becomes 
a smooth homogeneous mass of a semi-gelatinous consistence. We 
notice it here merely to remark on the circumstance that an agent 
in which Prussian blue is insoluble, should be found useful in ena-' 
bling it to combine with silk, cotton, wool, §c. The pure ferro- 
prussiate of iron is soluble in water, but the addition of a small 
portion of muriatic acid immediately precipitates it; wash away 
the acid by pure water, and the pigment becomes soluble again ; 
re-acidify, and it re-precipitates. 
20. Crystallization of the Sub-carbonate of Potash.—ll Dot..M. Fa- 
broni describes the following process for the crystallization of this 
salt, Make a solution of pearlash in water, and evaporate it until of 
specific gravity 1.57.. Allow it to cool, when all extraneous salts will 
be deposited; separate the fluid and again concentrate it until of spe- 
cific grav. above 1.6. The fluid will now be of a light green colour, 
and strong alkaline odour; place it in deep vessels, as glass jars for 
instance, and the sub-carbonate will soon crystallize in long rhom- 
boidal white lamine, situated vertically and parallel to each other; 
one extremity will touch the bottom of the vessel, and the other be 
attached to a saline crust on the surface of the liquid. When cold, 
the mother liquor will be found of specific grav. 1.6, but if further 
concentrated and again cooled, more crystals will be obtained ; and 
this may be continued until the whole has been crystallized.—Gior. 
di Fisica, vi. 451. 
21. Composition of Ancient Ruby Glass.—Mr. Cooper, on ana- 
lyzing a portion of this glass, sent to him by Mr.C. Muss, found 
it to contain silex, oxides of copper, iron, and silver, and lime. He 
considers the oxides of copper and silver as the colouring matter, 
but from the coloured portion being a film not more than 3},5 of an 
inch in thickness, upon the surface of the glass, it was impossible 
to ascertain their proportions. Iron existed abundantly in the un- 
coloured portion of the glass. Mr. Cooper thinks the alkali used 
as a flux for the siliceous matter is soda.—Ann. Phil. N.5. vii. 106. 
22. Detection of Arsenic in cases of Poisoning.—Mr. Phillips, in 
a very excellent practical paper on the methods of employing the 
various tests proposed for the detecting the presence of arsenic, 
has very much facilitated their use in certain cases, by pointing out 
that where the arsenic is mingled with a complicated mixture of 
animal and other substances, as when its presence is to be ascer- 
tained in fluids from the stomach, animal charcoal may be very 
advantageously employed as a preparatory agent. Some coloured 
