342 PROFESSOR CONNELL ON THE REACTION OF NATURAL WATERS 
with any spring, 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, 7. e., well, spring, and river 
waters, 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 lime 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 
current 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 simiJar short time as in the original experiments, and filtered. 
It was then found to be affected only very feebly either by oxalate of ammonia 
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. I 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 affected by acetate of lead; and any feeble 
deposit formed was not soluble in acetic acid, being sulphate of lead due to the 
sulphatesw hich had been added. 
It thus seemed evident that by the aid of carbonic acid no sufficient quantity 
