Miscellany. 
173 
Guimet, though it is not so intense. Introduce into a stone ware retort, 
coated with clay, a mixture of one part of kaolin, one and a half parts of 
sulphur, and one and a half parts of dry and pure carbonate of soda ; then 
heat gradually, as long as any vapours are disengaged, let the retort cool, 
break it, and there will be found in the interior a spongy mass of a very 
fine green colour, but on attracting moisture from the air, it passes gra- 
dually^ a blue. Wash the mass ; the excess of sulphate dissolves, 
and there remains a very beautiful blue. Wash by decantation, dry and 
calcine again at a cherry red heat, to expel the excess of sulphur. 
Ann, des Mines & Jimer. Journ % Sci< & Arts* 
Reduction of chloride of Silver. — The best mode of reducing the chloride 
of silver, is that of Mohr, which consists in mixing the chloride with one 
third of its weight of rosin, and heating the mixture gradually in a cruci- 
ble, until the flame loses its blue colour : after which, a strong heat is 
applied to melt the reduced silver. — Erdmann, Jour, and Idem, 
Mode of preparing Smoltz in Sweden. — The cobalt ore is roasted until 
most of its arsenic is expelled, after which a sufficient quantity of con- 
centrated sulphuric acid is mixed with it to form a thick paste, which is 
exposed to a moderate heat at first, and afterwards heightened to a cherry 
red, for one hour. The sulphate thus obtained is reduced to a powder, 
and dissolved in water; and a solution of carbonate of potash added to 
it in a gradual manner, in order to separate the iron, and when it is per- 
ceived by the blue colour that the cobalt is thrown down, the supernatant 
liquid is decanted and filtered, and the cobalt precipitated by a solution 
of silicate of potash, which is prepared by heating in an earthen crucible, 
a mixture of ten per cent, of potassa, fifteen of well pulverized quartz, 
and one of charcoal, and treating the melted mass with boiling water. 
Diet. Tech. and Idem. 
Purification of Water. — In order to precipitate the earths mechanically 
suspended in water, it is recommended to employ the silicate of potassa, 
gelatinous silica or phosphoric acid. The last is an excellent reagent 
for throwing down the oxide of iron, without introducing any foreign 
principle in the water. 
Ann. des Mines and Idem. 
Balsam Copaiva. Mr. Webster says that at Para, the balsam copaiva 
is esteemed a capital vermifuge in large doses, and is sometimes used to 
mix paint with ; it gives work the appearance of being varnished. The 
seeds are large and black, and are kept in apothecaries' shops as' an as- 
tringent; they contain a quantity of oil, and some hydrocyanic acid. The 
tree is very large and lofty, and is used for timber. 
Voyage to South Atlantic, IL 
