Chemical Science. 165 
tity of plaster of Paris, moistening and moulding the whole into 
bricks, which may be burnt like bricks of clay.—Ann. de Chim. 
xxiv. 271. 
14. Preparation of Saturated Hydro-sulphuret of Potash or 
Soda.—The following is M. Berthier’s process: mix ten sulphate of 
potash, ten sulphate of baryta, and five powdered charcoal, or 
eight dry sulphate of soda, ten sulphate of baryta and five pow= 
dered charcoal, and heat them to whiteness in a crucible. Double 
sulphurets are obtained, which are greyish, half-fused, and easily 
separated from the crucible; they contain each an atom of the 
composing sulphurets. Pulverize and introduce them gradually 
into a flask three-fourths filled with warm water, close it and fre- 
quently agitate it; when saturated, the water will contain an atom 
of the sub-hydrosulphuret of alkali and an atom of sub-hydro- 
sulphuret of baryta. Diluted sulphuric acid is then carefully 
added to the solution in the flask, by small portions at a time, agi- 
tating éach time and preserving the flask well closed. In this 
way the baryta is precipitated, and its sulphureted hydrogen goes 
to the alkali; when all the earth has fallen, the fluid is left to be- 
come clear, is decanted and tested by solution of salts of lime or 
magnesia. If a precipitate occurs, a fresh portion of hydrosul- 
phuret of baryta must be added to the liquor and precipitated by 
sulpburic acid. With a little care, a neutral hydrosulphuret of the 
alkali is obtained, which contains neither baryta or sulphuric acid, 
but of the two it is better to have the acid in excess.—Ann. de 
Chim. xxiv. 279. 
15. Preparation of Kermes Mineral.—According to M, Fabroni, a 
much finer kermes mineral is obtained by using tartar in place of the 
alkali employed in the usual process. Three or four parts of tartar 
should be mixed with one part of powdered sulphuret of antimony, 
and heated red in a crucible until the cessation of fumes indicates 
that the tartar is all decomposed ; the mass is then to be dissolved 
in hot water, filtered and left to cool, when abundance of fine 
kermes will be deposited, of a very deep colour. ‘The abundance 
of kermes thus obtained does not at all interfere with the quantity 
and beauty of the golden sulphuret, afterwards obtained by the ad- 
dition of acid to the mother liquor.—Ann. de Chim. xxv. 7. 
16. Action of Sulphur on Iron.—Col. A. Evans has remarked, 
that although sulphur has so strong an action on heated wrought 
iron as immediately to form holes in it, yet it does not at all affect 
grey castiron, A plate of wrought iron, 63 of an inch in thick- 
ness, heated to whiteness, and held against a roll of sulphur ~§; of 
an inch in diameter, was in fourteen seconds pierced through with 
perfectly cylindrical hole. Another bar about two inches in 
