WITH SOLUBLE LEAD SALTS. 



361 



POSTSCRIPT. 



Since this paper went to press, I have ascertained that the town water of 

 St Andrews, which is one of those which gives the reaction referred to with lead 

 salts, yields by evaporation, after having been boiled and filtered, ^ji^ of its 

 weight of carbonate of lime. Other waters may of course contain more. I also 

 observe, that Feesenius found, that when distilled water was boUed a long time 

 (probably, from the context, several hours) with freshly precipated carbonate of 

 lime, so as to form a saturated hot solution, and this solution was then kept for 

 four weeks at common temperatures, in contact with undissolved carbonate of 

 lime, under frequent agitation, it yielded by evaporation j^ggj of its weight of 

 carbonate of lime. — Liebig's Annalen, July 1846. In so far as regards spring 

 waters, it is unnecessary to say, that Nature does not take such pains to charge 

 them with lime. The method suggested above seems a more simple one, and may 

 often be as effectual, possibly even more so ; when the stiU more simple means 

 of free carbonic acid are not brought into play. From the experiments of Fee- 

 senius, it appears, that carbonate of lead is much less soluble in water than car- 

 bonate of lime, viz., in 50,551 parts, which is quite conformable to the results 

 above stated. 



VOL. XVI. PART lU. 



4 Y 



