666 poisons : their effects and detection. | § 846 . 
Special Tests for Salts of Copper. — Hydrazine Sulphate. —A 3 per 
cent, solution of hydrazine sulphate added to-a solution of a copper 
salt, in presence of an excess of sodium hydroxide, precipitates the 
copper as metallic copper ; the metal may be filtered off, dried, ignited, 
and weighed as cupric oxide. 1 
Quinosol. —Quinosol, an antiseptic in commerce, is the potassium 
salt of 8-hydroquinoline-j8-sulphonic acid. A solution in water of 0-1 per 
cent, gives a yellow precipitate with copper salts in quite small quantities. 2 
Diphenyl-Carbazide Test. —A cold saturated solution of the carbazide 
in benzene, agitated with an aqueous solution of a copper salt, produces 
a violet compound which dissolves in the benzene. 3 Carbazide gives 
colours similarly with a number of metals, but the hue of the copper 
compound differs from all others. 
Formaldoxime. —Formaldoxime is made by adding hydroxylamine 
hydrochloride to formaldehyde in solution in the proportion 1 : 5. This 
solution is mixed with the solution to be tested for copper and a slight 
excess of potash solution ; should copper be present, a violet colour 
results. It is stated that one part per million of copper in aqueous 
solution may be detected by this reagent. 4 
The Bromine Test. —On evaporating a solution containing a copper 
salt to dryness, and then adding bromine water and again evaporating 
to dryness, a black residue of copper bromide is formed ; this will, 
according to Vitali, detect one part of copper sulphate in a million of 
water. 5 
Micro-Chemical Tests for Copper. —A dilute solution of a copper 
salt, to which ammonia has been added, gives a precipitate with 
potassic ferrocyanide of ammonium ferrocyanide of copper (Fe(CN) 6 Cu 2 , 
4NH 3 , H 2 0) in pale yellow, characteristic crystals ; the crystals, without 
changing their form, gradually lose ammonia, and then the colour 
becomes a red-brown or brick-red. 
A copper salt dissolved in a concentrated solution of potassium 
nitrite, to which acetic acid in excess has been added and then a small 
fragment of lead acetate, is converted into a triple nitrite of potassium, 
copper, and lead, 2N0 2 K, (N0 2 ) 2 Pb, (N0 2 ) 2 Cu 6H 2 0 ; this salt is in 
highly refractive.cubes, and is very characteristic. 
§ 846. Volumetric Processes for the Estimation of Copper. —A 
number of volumetric processes have been devised for the estimation of 
copper, but for the purposes of this work it is unnecessary to detail them. 
When copper is in too small a quantity to be weighed, it may then be 
estimated by a colorimetric process. 
1 Paul Jannasch and K. Biedermann, Ber., 1900. 
2 J. E. Saul and David Crawford, Analyst, 1918. 
3 Paul Cazeneuve, Compt. Rend., 1900. 
4 Dunstan and Rossi, Journ. Chem. Soc., T., 1898; A. Bach, Compt. Rend., 1899. 
f> 1). Vitali, Boll. Chim. Farm., xxxviii. 
