Lead in English Chemical Preparations. ‘269 
was perceived, showing that the carbonate of lead was merely 
dispersed in the water and not dissolved. A similar effect 
was shown by oxide of lead treated with pure water, but no 
solution of it was perceptible if it was kept with the water, 
whether in an open or a closed vessel 3—a fact which is op- 
posed to the received opinions*. Well-water and mineral 
water corrode lead, forming a coating of oxide of lead on the 
metal without taking up a particle of the oxide; but mineral 
waters strongly impregnated with carbonic acid gas I found to 
‘contain faint traces of lead, when they had been for some time 
in contact with it. Mr. Walker according to his analysis found 
in the mineral water of Bath, lead originating from the pipes 
or pump used for the conveying of the water. (Quarterly 
Journal of Science, Literature, and Art, January to March, 
1829.) Might not the lead in these instances be dispersed 
mechanically in the water? The result of my experiments 
induces me to believe so. 
Volatile oil dissolves lead freely. Alcoboland gether, when 
pure, do not act on that metal. When an alkaline fluid contains 
a trace of lead, the best test to apply is the hydrosulphuret of 
ammonia, as this reagent will detect s00.000 gt: of crystallized 
acetate of lead; but this is almost the limit of its dilution, as 
the observation must be made by the light falling upon the 
surface of the liquid, which must have a diameter of not much 
less than one inch. In a neutral fluid, or in one which is only 
slightly acid, the presence of lead may be shown by the appli- 
cation of sulphuretied hydrogen gas; but it is advisable to avoid 
the use of nitric acid, as by a little surplus of it faint traces of 
lead will be easily overlooked. Acetic acid is preferable be- 
cause its surplus does not affect the delicacy of the hydrosulphu- 
retted gas. Very good tests also are soluble sulphates and chro- 
mates, particularly to decide on the nature of the metal, al- 
though not to such an extent as the tests before mentioned, 
Chromate of potash will indicate traces of lead, when sulphate 
of soda ceases to do so. Sulphate of lead will be partly dis- 
solved by concentrated nitric acid ; muriatic acid shows traces 
of lead; acetic acid only faintly shows them. Chromate of 
lead when treated with strong sulphuric acid will be changed 
into sulphate of lead, and the decanted acid will contain no 
lead. Nitric acid dissolves traces of lead from the chromate; 
muriatic acid changes the chromate of lead into chloride of 
lead and the chromic acid into oxide of chrome by develop- 
ing chlorine, particularly by the application of heat. Acetic 
* Handbuch der theoretischen Chemie von Leopold Gmelin, 1 Band, 2 Abth. 
P. 1073. [See on this subject Capt. Yorke’s paper in Lond. and Edinb. 
bil. Mag., vol. v. p. 81.—Kprr.] 
