342 PROFESSOR CONNELL ON THE REACTION OF NATURAL WATERS 



witli any sprinsr, well, or river water, not coming under the denomination of a 

 mineral water, which contained so much of any chloride as to be indicated by a 

 lead salt. The chloride of lead is too soluble to become visible, unless where the 

 contamination is considerable. The portion of the precipitate not soluble in acetic 

 acid is usually due to the presence of some sulphate. 



Taking the fact as I have now ascertained it to be, that natural waters which 

 have passed through the strata or soils of the earth, i e., well, spring, and river 

 M-aters, very commonly or invariably yield, even after boiling, and filtering, if ne- 

 cessary, a greater or less amount of precipitate with acetate of lead, readily dis- 

 solved, in whole or in part, by acetic acid with effervescence ; in other words, 

 that such natural waters contain frequently or invariably, even after boiling, one 

 or more dissolved carbonates, the question arises. What is the nature of such car- 

 bonate .'' As these waters, when they have been much concentrated after being 

 boiled and filtered, and have then been made up to their former bulk by distilled 

 water, are found to have lost their power of shewing the same phenomena as be- 

 fore with lead salts, and to have deposited carbonate of lime during concentration, 

 the effect must have been due to this carbonate of lime whilst held in solution. The 

 farther question, therefore, arises, how this carbonate of Ume came to be dissolved ? 



I tried to ascertain whether water would dissolve carbonate of lime in its 

 nascent state as precipitated by boiling a solution in excess of carbonic acid. A 

 cmTcnt of carbonic acid was passed through lime water prepared with distilled 

 water, until the precipitate at first formed was redissolved. The solution was 

 then boiled for a similar short time as in the original experiments, and filtered. 

 It was then found to be affected only very feebly either by oxalate of ammonia 

 'S. or by acetate of lead ; the action being not at all equal to that produced on boiled 



natural waters by these reagents. The carbonate of lime in the act of precipita- 

 tion by boiling, had evidently not been dissolved except in very insignificant 

 quantity by the water. 1 then, before boiling the solution, exposed it for a day to 

 the air in an evaporating basin, after keeping it for some days in a close vessel ; 

 but did not find that the quantity of carbonate retained after ebullition, short 

 subsidence, and filtration, was increased. 



As it was possible that some of those saline matters contained in natural 

 waters might promote the solubility of carbonate of lime, minute quantities of 

 solutions of muriate of lime, sulphate of lime, muriate of magnesia, and chloride 

 of potassium were added to lime water prepared with distilled water. A current 

 of carbonic acid was then conducted through the liquid so as to redissolve the 

 precipitate which it at first caused. The liquid, after ebullition, short subsidence, 

 and filtration, was found scarcely to be aff'ected Ijy acetate of lead ; and any feeble 

 deposit formed was not soluble in acetic acid, being sulphate of lead due to the 

 sulphateswhich had been added. 



It thus seemed evident that by the aid of carbonic acid no sufficient quantity 



