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(64857 Gh) 
XXIII.—On the Reaction of Natural Waters with Soluble Lead Salis. By Artuur 
ConnELL, Esq., F.R.S.E., Professor of Chemistry in the University of St Andrews. 
(Read 19th January 1846.) 
In a former communication to the Society, I noticed a reaction presented 
by all spring, well, and river waters which I had examined, that, even after 
being boiled, they yielded, with acetate of lead, a precipitate readily soluble, in 
whole or in great part, in acetic acid. This easy solubility in acetic acid shewed 
that the precipitate was neither a sulphate nor a phosphate, and the comparatively 
slight action of nitrate of silver proved that it was not a chloride. There seemed, 
therefore, to remain only the conclusion that it was either acarbonate, or was due to 
organic matter. The former alternative, of course, depended on whether the solu- 
tion in acetic acid was attended with effervescence or not; and as this seemed usually 
not to be the case, and as, on decomposing some of the precipitate by sulphuret- 
ted hydrogen, some organic matter in solution was obtained, the conclusion seemed 
to be, that the appearance was caused by organic matter, probably of the nature 
of the crenic and apocrenic acids of Berzetius. I have since, however, found that 
by very careful observation, effervescence may be noticed during the solution of 
the precipitate more frequently than I at first supposed. It is not so easy as 
might be imagined to determine this point. If acetic acid is added before the 
precipitate has subsided, no effervescence can be noticed, in almost any case, from 
the water dissolving the carbonic acid evolved and diffused through the whole 
liquid. And even when allowed to subside, and the greater part of the liquid is 
decanted, the addition of acetic acid not unfrequently causes solution without 
apparent effervescence. The cautious addition, however, of a heavier acid, such 
as the nitric or even the muriatic, after allowing the lead precipitate to collect at 
the bottom, and decanting the greater part of the liquid, seldom fails to shew the 
effervescence where a carbonate is really present. 
In so far, then, as the precipitate is dissolved by acids with effervescence, we 
may conclude that it has been caused by some carbonate remaining dissolved 
after boiling the water; and in so far as the solution may not exhibit efferves- 
cence, we may conclude that it is due to organic matter, provided silver salts do 
not indicate the presence of a sufficient quantity of chlorides, and provided acetic 
acid instantly causes solution in whole or great part. In some instances I have 
found that acetate of lead does not yield a precipitate, wnless the water has been 
previously boiled, a circumstance obviously due to excess of carbonic acid retain- 
ing the carbonate of lead in solution. In regard to chlorides, I have never met 
VOL. XVI. PART III. 4x 
