ON THE DETECTION OP ARSENIC. 
283 
low flocks; the addition of a few drops of hydrochloric acid 
produces this effect instantly and the precipitate formed enjoys 
the property of re-dissolving in liquid ammonia, and again to 
be separated by the acids. 
3d. Saturated by several drops of alcoholic potash, this so- 
lution produces with nitrate of silver a flocculent canary-yel- 
low precipitate, which becomes brown by the action of light, 
and a fine herb green precipitate (deuto-arsenite of copper) 
with the deuto-sulphate of copper. With the ammoniacal sul- 
phate of copper, this last effect is produced in a solution of ar- 
senious acid unsaturated by the potash. 
4th. By evaporating to dryness, the solution of arsenious 
acid, saturated by the potash, mixing the residue with a little 
charcoal, and calcining it by the flame of a spirit lamp, in a 
small tube drawn out slender at one end as represented in the 
plate fig. 1, you obtain at a small distance from the heated 
point a brilliant encrustation of metallic arsenic, which adheres 
to the sides of the tube, and gives to it the appearance of mir- 
rored glass. 
5th. A small quantity of powdered arsenious acid, intimately 
mixed with a little black flux (a mixture of carbonate of potash 
and finely divided charcoal, obtained by deflagrating in a cru- 
cible heated to redness, 2 parts of cream of tartar and 1 of ni- 
tre,) also furnishes a like result upon calcining this mixture in 
a glass tube drawn out to a point. 
6th. Again, the reduction of arsenious acid may be effected 
upon minimum quantities, according to Berzelius, by the fol- 
lowing process: Draw out by means of a spirit lamp, a com- 
mon tube so as to taper it down to the diameter of a strong 
knitting needle ; then close the narrow extremity several 
inches distant from the point whence drawn. Introduce a 
small grain of arsenious acid in the closed end, a, (see fig. 2,) 
and place over it as far as b, small particles of very dry charcoal; 
hold the tube horizontally in the flame of a spirit lamp, so as 
at first to heat only the charcoal, and when this is heated to red- 
ness, carry the flame to the extremity of the tube a, where 
the arsenious acid is contained. This, in volatilizing, is reduc- 
ed by the contact of the heated charcoal, and condenses at a 
