194 ») -.\.\ > Green Ore of Uranium. 
toe dissolves in the boiling water, forming a somewhat 
viseid liquid, which envelopes every particle of the precipi- 
tated calcareous salt (usually Selenite, sometimes Carbonate 
of Lime) renders them slippery, so to speak, and prevents 
their mutual contact: and cohesion. After a month’s ser- 
vice, the boileris emptied, and new potatoes added along 
with the charge of water. ; 
22. Flowers of the common Mallow (Malva Sylvestris) 
an excellent Testof Alkali —M. M. A. Payen and A, Cheva- 
lier state,that an alcoholic infusion of these flowers (previously 
dried by a steam heat out of contact of light) gives a sen- 
sible tinge of green on being mixed with water containing 
moon Part of potash, 1, part of Carbonate of Soda and 
3; of lime water. 
_ According to the same chemists, the colouring matter of 
the fruit of the Cerasus Mahaleb (wood of St. Lucie,) isan 
excellent test of acids, but inferior in delicacy to litmus. 
Infusions are more sensible to change of colour than colour- 
ed paper. Ae . 
23. Method of colouring Alum Crystals.—In making these 
crystals, the colouring should be added to the solution of 
alum in proportion to the shade whichit is desired to produce. 
Coke, with a piece of lead attached to it, in order to ma 
it sink in the solution, is the best substance for a nucleus; 
or if a smooth surface be used, it wiil be necessary to wind 
it round with cotton or worsted ; otherwise no crystals will 
adhere to it. 
Yellow.—Muriate of iron. 
Blue.—Solution of Indigo in sulphuric acid. 
Pale Blue.—Equal parts of alum and blue vitriol. 
Crimson.—Infusion of Madder and Cochineal. * 
Black,—Japan ink, thickened ED CAT oc a 
dpe eT) di of alum and blue vitriol with a few 
drops of muriate of iron. ; 3 2 
_ Milk pale crystal i alum held over a glass contain- 
ing ammonia, the vapour of which precipitates the alumina 
anit surface 
24. Green Ore of Ur anium.—R. Philli has ascertained 
that the green ore of Uranium Frou taiomele contains 
