68 



PROCEEDINGS OF THE AMERICAN ACADEMY 



ments. The bars were covered, in test-tubes of a given diameter, with 

 fifteen cubic centimetres. 



" After exposure out of direct sunlight, except where otherwise 

 stated, a length of time indicated in the column of days at the left, a 

 suite of similar tubes was filled to the requisite depth with correspond- 

 ing waters, and the bars transferred with the least delay. 



"The waters were then acidulated with acetic acid, received each a 

 drop of acetate of potassa, — ■ which Fresenius has observed decomposes 

 all lead salts not decomposed by hydrosulphuric acid, — and exposed 

 to a stream of washed hydrosulphuric acid till the liquid became clear, 

 if it had been at first discolored by the precipitate of lead. If concen- 

 tration occurred, it is so stated. The quantities were estimated by a 

 method to be described farther on. 



"Table I. 



" Table II. — Experiments with Lead to ascertain the Action of 

 Water on Successive Days. — One bar resting on the bottom of each 

 test tube. Waters replaced at the date of each result. 



