94 PROCEEDINGS OF THE AMERICAN ACADEMY 



moreover, satisfied that, had Thompson and Philips concentrated the 

 filtrates which they supposed to contain no lead, they would have de- 

 tected it without difficulty. A flask containing distilled water and lead 

 shavings was corked and placed aside for a few days. A deposit of 

 carbonate and hydrate of lead formed around and upon the lead shav- 

 ings. The contents of the flask were carefully poured upon a double 

 filter of Swedish paper, and the filtrate concentrated. It gave a distinct 

 precipitate with hydrosulphuric acid. 



" Tea and Coffee Grounds unite with Lead in Solution. — It has 

 been an occasion of surprise, that numerous families have for a long 

 period employed well-water that corroded leaden pipe so rapidly as to 

 require replacement in from six to eighteen months, and yet, so far as 

 they or their physicians know, have suffered no illness attributable to 

 the water. This fact suggested two considerations : — 1st. Are all 

 lead compounds equally poisonous ? 2d. If so, is the quantity which 

 finds its way into the organism sufficient to produce the maladies attrib- 

 uted to lead ? It may be assumed that water flowing directly through 

 a leaden pipe of an inch bore and not more than thirty feet in length 

 will ordinarily be identical in constitution with that in the source from 

 which it is drawn. That only which has been some time at rest would 

 be expected to contain lead. Accordingly, there is more care that the 

 water first drawn be thrown away. The first morning draught is 

 usually in the form of tea or coffee. The following experiments throw 

 light upon this point. To boiling water containing lead in solution tea 

 was added, in the quantity usually taken in the preparation of the bev- 

 erage (a gramme to 50cc.), the temperature maintained three minutes 

 just below the boiling point, and the decoction filtered off. The filtrate 

 was evaporated to dryness, ignited, redissolved, and the precipitate with 

 hydrosulphuric acid made and estimated as already described. 



" I. 50cc. of lead solution, containing one thousandth of its weight of 

 lead, with Igr. of black tea, lost ninety-nine hundredths of its lead. 

 Originally present, 0.05gr. of lead. 



After separation from the grounds, 0.0005 " 



" II. 55cc. of solution containing one tenth as much lead as the 

 above, with the above quantity of tea, lost more than eleven twelfths 

 of its lead. 



Originally present in solution, 0.005gr. of lead. 



After separation from the grounds, 0.0004 " 



" The experiments with coffee yielded the following results : — 



