Chemical Science. 445 
Hydrogen Gas in Sulphureous Mineral Waters, by M. Desfosses, 
of Besangon.—After pointing out the uncertainty and difficulty 
of the ordinary methods, he recommends the use of bin- 
acetate of copper, from which sulphuretted hydrogen throws 
down a sulphuret of copper, whose weight will indicate the 
quantity of sulphur; and, consequently, the quantity of sul- 
phuretted hydrogen may be thence inferred. He gives some 
experimental proofs of the accuracy of this plan of analysis, 
and applies it to the examination of the sulphureous waters of 
Guillon, near Baume-les-Dames, in the department of the 
Doubs. He adds to the water in question a solution of bin- 
acetate of copper, till the mixture loses its sulphureous odour. 
He then collects and dries the precipitate. These waters con- 
tain, in 6 kilogrammes, 
MCHBAIL ota ae. Sh yall ey Sup eORts 
Carbonate of lime . . . 0.700 
Carbonate of magnesia . 0.227 
Insoluble residuum . . 0.020 
2.467 
Gaseous products. 
Free sulphuretted hydrogen . . 65centim.cub, 
Carbonic acid. . . « . . . 100 
AZO C6 nti bts aos (die Sa eh Aa 
Jour. de Phar., Oct. 1822. 
25. Flowers of the Common Mallow, (Malva Silvestris; an 
excellent Test of Alkali. MM. A. Payen and A. Chevalier 
state, that an alcoholic infusion of these flowers (previously 
dried by a steam heat out of contact of light) gives a sensible 
tinge of green on being mixed with pure water containing 
zodone part of potash, 4455 part carbonate of soda, and A. of 
lime-water. 
According to the same chemists, the colouring matter of the 
fruit of the cerasus mahaleb (wood of St. Lucie) is an excellent 
test of acids, but inferior in delicacy to litmus. Infusions are 
more sensible to change of colour than coloured paper. 
26. Method of Colouring Alum Crystals.—In making these 
erystals the colouring should be added to the solution of alum 
in proportion to the shade which it is desired to produce. 
Coke, with a piece of lead attached to it, in order to make it 
sink in the solution, is the best substance for a nucleus; or, if a 
smooth surface be used, it will be necessary to wind it round 
with cotton or worsted, otherwise no crystals will adhere to it, 
Yellow.—Mutiate of iron. 
Blue.—Solution of indigo in sulphuric acid. 
Pale Blue.—Equal parts of alum and blue vitriol. 
