74 



PROCEEDINGS OF THE AMERICAN ACADEMY 



" The effect of temperature was sought in a variety of ways.* The 

 following experiments are recorded. 



" Table XIV. — Experiments with Bars previously coated, ex- 

 posed to direct Sunlight from the 2lst to the 26th of June. — Bars 

 resting on the bottom of the tubes. 



" Tlie influence of extreme temperature and exposure to air and 

 moisture, under the most favorable circumstances, was ascertained by 

 transmitting steam mixed with air through a leaden pipe thirty-six feet 

 long, coiled like a still-worm, and placed in cold water to produce con- 

 densation. One hundred and ten cubic centimetres of the condensed 

 water, after acidulation with acetic acid, were treated with a stream of 

 hydrosulphuric acid. The precipitate was collected on a filter, pre- 

 viously dried at 100° C, and gave 0.0225gr. of sulphide of lead, equal 

 to 0.0196gr. of lead ; which is equivalent to 0.8095gr. of lead in a gal- 

 lon. Whatever influence might result from such changes, it must be 

 remembered that pipes under ground will preserve a tolerably even 

 temperature ; and be the effect of increased heat what it may, it has 

 been more energetic in Philadelphia than it ever can be in Boston. 



" The effect of increasing the percentage of common salt is exhibit- 

 ed in the following table. 



" Table XV. — Experiments with Cochituate Water and graduat- 

 ed Solutions of Common Salt. — Bars and volumes as in the foregoing 

 experiments. No concentration. Bars resting on the bottom of the 

 tubes. 



* Dr. Hayes has observed that elevation of temperature increases the quantity of 

 lead dissolved in a given time. — Re/port of the Consulting Physicians^ 1848, p. 24. 



