IN THE PUREST WATERS FROM TERRESTRIAL SOURCES. 419 



less than that afforded by acetate of lead. Silver salts produce merely a decided 

 opalescence, not a trace of any dense precipitate. 



To a large stoppered bottle containing several quarts of this water, acetate of 

 lead was added as long as a precipitate was produced. The stopper was then re- 

 placed, and the bottle left twenty-four hours undisturbed, when the precipitate was 

 found to have entirely subsided to the bottom. The clear liquid was then cautiously 

 decanted by a glass syphon, 2 or 3 ounces of liquid only being left. A current of 

 sulphuretted hydrogen was then conducted through a long tube into this liquid, 

 and the precipitate well stirred up. The liquid was then filtered and heated, to 

 drive off the excess of sulphuretted hydrogen. A colourless solution was thus 

 obtained, which reddened litmus powerfully, and of course [contained sulphuric 

 acid, proceeding from the decomposition of the sulphate of lead precipitated from 

 the water, after a certain interval. When a portion of it was evaporated to dry- 

 ness in vacuo over sulphuric acid, the residual matter was deliquescent, from the 

 presence of sulphuric acid. This residue, when redissolved, left some flocky 

 matter, and when ignited a little oxide of iron remained. That the liquid ob- 

 tained, however, also contained some organic matter, was evident from the fol- 

 lowing circumstances. Saturated with potash, and evaporated in vacuo, it yielded 

 a white crystalline mass, mixed with darker matter ; and when this saline sub- 

 stance was heated to redness in a tube retort, it yielded vapour having a strong 

 empyreumatic smell, and left a black coaly mass ; and turmeric paper was occa- 

 sionally made brown by its vapour, although this reaction could not always be 

 distinctly observed, perhaps from the small quantity of matter heated. The acid 

 liquid itself scarcely affected solution of acetate of copper ; but when the acetate 

 was made neutral by ammonia, or when the potash salt was used, although there 

 was no immediate change, a greyish- white precipitate formed in a day or two. 

 With persulphate of iron, made as neutral as possible by ammonia, the potash 

 salt gave no precipitate at first ; but a little was formed after a day or two. 

 Nitrate of silver was scarcely affected by the liquid. Both the neutral and the 

 basic acetate of lead were abundantly precipitated by it, and the precipitate shewed 

 no trace of effervescence when acted on in mass by acids. The liquid evidently 

 contained the same matter which originally affected the lead salt in the water em- 

 ployed ; for when the potash salt was diluted with five bulks of distilled water, 

 and acetate of lead added, a cloud was produced as in the original water, dissolved 

 by acetic acid ; soon after which, a precipitation of sulphate of lead commenced. 



It appears to me that the legitimate conclusion from all these experiments is, 

 that the original action on the lead salt was due to organic matter in the water 

 employed. The precise nature of that organic matter they are hardly sufficient 

 to determine, although it would rather appear to be an azotised substance, ana- 

 logous, perhaps, to the crenic acid ; and the flocky matter which I always observed 

 to separate when the solutions were evaporated and redissolved, was in all like- 



