1891.] 



109 



[Warwick. 



I. Influence of Dilution upon the Precipitation of Copper. 



Copper present 



iu grams. 



(1) .0717 



(2) .0358 



(3) .0170 



(4) .0089 



(5) .0044 



(6) .0022 



(7) .0011 



Copper 



found. 



.0199 

 .0111 

 .0057 

 .0028 

 .0014 

 .0006 

 .0002 



Free acid. 



3 drops 

 3 << 



3 << 



c.c. H 2 0. 



100 



e.c. H< > gas Time in 

 perniiuute. hours. 



1.75 1 



The distance between the poles was 2.5 cm. The area of the electrodes 

 was (3.8 cm. X 3.17 cm.) x 2. The deposition was performed in beakers, 

 having a capacity of 400 c.c, a height of 10 cm. and 7.6 cm. in diameter. 

 The deposit was bright and adherent and, although the amount of free 

 acid present was very small, the metal was not spongy. The results 

 obtained were in close accord with those assigned by theory, according to 

 the law that the amount of metal deposited in a given time is proportional 

 to the strength of solution. 



II. The Influence of Temperature upon the Precipitation of 



Copper. 



Free acid. 



c.c. HoO. 

 150 c.c. 



Time in 



hours. 



Temperature in 

 degrees Cent. 



20° 

 40° 

 60° 

 80° 



The area of the electrodes was (3.5 cm. x 3.8 cm.) x 2. Distance be- 

 tween poles 2.8 cm. The current gave 1.25 c.c. HO gas per minute. (1) 

 was slightly spongy and had a slight deposit of basic green salt at the top. 

 (3) was somewhat dark and slightly spongy at the top but adherent. The 

 amount of metal deposited increased with rise of temperature, as follows : 

 .0027 grams (200-40°), .0034 grams (40°-60°), .0039 grams (60°-80°). 

 The ratio of increase also rose with the temperature, being greatest be- 

 tween 60° and 80°. In the above series the determinations were made in 

 neutral solutions ; in the following, 15 c.c. of formic acid was added. 



