74 



PROCEEDINGS OF THE AMERICAN ACADEMY 



The 



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

 following experiments are recorded. 



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

 posed to direct Sunlight from the 21s/ to the 26th of June. — Bars 



resting on the bottom of the tubes. 



"The 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. — Rtjwrt of the Consulting Physicians, 1848, p. 24. 



