6j2 poisons : THEIR effects and detection. [§§ 855 - 857 . 
from free oxalic acid) in dilute hydrochloric acid, and lastly, titrating by 
permanganate. The absence of free hydrochloric acid before precipitat¬ 
ing must be ensured. 
Electrolytic Estimation. — An adherent deposit of bismuth from 
the sulphate or nitrate, suitable for quantitative estimation, may be 
obtained by dissolving up to 0-6 grm. with 3-4 grins, of carbamide or 
formaldehyde or acetaldehyde in 5-6 c.c. nitric acid and diluting to 150 
c.c. with water ; the solution may be warmed to from 80°-90° ; the 
current density should be from 0-04-0-08 ampere, and the E.M.F. from 
1-5-1-9 volts. The precipitated metal is washed without stopping 
the current, and ultimately dried at 100° C. 1 
Karl Wumnenauer 2 uses 1-2 c.c. of glycerol, and lays stress on the 
importance of agitating the solution constantly (which is easiest effected 
by using a rotating cathode). He recommends a current of 0-1 ampere ; 
this, should indications of peroxide be detected, is reduced to 0-05 ampere. 
The temperature of the solution is to be raised to 50° and maintained at 
that temperature. 
4. SILVER. 
§ 855. Silver = 108; specific gravity, 10*5; fusing-point, 1023° 
(1873° F.).—Silver, as separated in analysis, is either a very white, 
glittering, metallic bead, or a dull grey powder. It does not lose weight 
on ignition, and is soluble in dilute nitric acid. 
' § 856. Chloride of Silver, AgCl = 143-5—specific gravity, 5-552 ; 
Ag, 75-27 per cent. ; Cl, 24-73 per cent.—is a dense, white, curdy 
precipitate when produced in the wet way. It is very insoluble in 
water, dilute nitric acid, and dilute sulphuric acid ; in many warm 
solutions (especially aqueous solutions of the chlorides generally, the 
alkaline and alkaline-earthy nitrates, and tartaric acid solutions) the 
silver is dissolved to an appreciable extent, but deposited again on 
diluting and cooling. The complete solvents of chloride of silver are— 
ammonia, cyanide of potassium, and hyposulphite of soda. Chloride 
of silver cannot be fused at a high heat without some slight loss by 
volatilisation ; on charcoal in the reducing flame, it fuses very easily to 
a globule. It can with soda be reduced to metal, and can also readily 
be reduced by ignition in a current of hydrogen, carbon oxide, or 
carburetted hydrogen gas. 
§ 857. Sulphide of Silver, Ag 2 S = 248—specific gravity, 7-2 ; Ag, 87-1 
per cent. ; S, 12-9 per cent.—when prepared in the wet way, is a black 
precipitate, insoluble in water, dilute acids, and alkaline sulphides. If 
ignited in hydrogen it may be reduced to the metallic state ; it is soluble 
in nitric acid, with separation of sulphur. 
1 Dmitry Balachowsky, Compt. Rend., cxxxi. 1900. 
2 Zeit. anorgan. Chemie, xxvii., 1901. 
