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SELECTED ARTICLES. 
flocculent, and sometimes gelatinous form ; however, the 
precipitation is not complete, and by evaporation a small 
quantity of cetrarine can always be obtained. 
Dry cetrarine is, on the contrary, changed to a yellow and 
then to a brown color, by concentrated sulphuric acid. It 
then forms a brownish red, afterwards a vinous blood red 
solution entirely precipitable by water. The precipitate 
formed by this last mode, presents all the properties of ulmine. 
Concentrated nitric acid converts it into a yellowish brown 
resin and oxalic acid, giving off, at the same time, nitric oxide. 
Phosphoric acid changes it gradually, by the aid of heat, into 
ulmine. 
The action of hydrochloric acid on cetrarine is altogether 
interesting, changing it, especially if assisted by a gentle 
heat, into a blue colored matter, which dries in the light into 
a bright blue mass, but which in water or weak acids takes a 
less deep tint. This matter is but slightly soluble in water, 
alcohol, &c, and has, moreover, a bitter taste; the alkalies 
change it very promptly into ulmine. It dissolves in concen- 
centrated sulphuric acid, to which it communicates a deep 
blood red color; colorless concentrated nitric acid produces, 
with it, a solution of a beautiful color, which varies from a 
rose to a carmine red. It dissolves with a yellow color in 
nitric acid in excess, and if water has been added, at the be- 
ginning, to this solution, or rather to that by sulphuric acid, 
the coloring matter may be reproduced without alteration. 
This blue of cetrarine is not formed when dry hydrochloric 
acid gas is passed upon cetrarine, or when this latter is heated 
in an atmosphere of the gas. At common temperatures cetra- 
rine does not absorb the gas at all; and when heat is applied, 
absorbs it but imperfectly, becomes brown, and carbonises, giv- 
ing rise to hydrocarburet of chlorine, and the volatilization of 
an orange red liquid, and a semi-solid mass of a fine carmine red. 
Tannic and gallic acid cause no sensible change in solutions 
of cetrarine. 
Cetrarine unites in fixed proportions with the alkalies and 
alkaline earths, without destroying their reaction on vegetable 
