1891.] 



113 



[Warwick. 



(1), (3), (5) and (6) were very spongy. In (4), (10) and (11) no deposition 

 of metal took place, (12) was spongy and w r as covered with a white coat- 

 ing of zinc hydrate. At 80° no metal was deposited in the presence of 

 free acid provided the current was not too strong. The ratio of decrease 

 with rise of temperature was (20°-40°) 10 grams, (40°-60°) 9 grams, (60°- 

 80°) no deposit. The distance between the poles was 2.85 cm. Area of 

 electrodes (3.8 cm. X 3.16 cm.) X 2. Duration of experiment, one hour. 



III. Influence of Pole Separation upon the Precipitation of 



Zinc. 



Area of electrodes (3.8 cm. x 3.48 cm.) X 2. The deposit was firm and 

 compact. Compared with the results obtained with copper and cadmium, 

 the result in (4) is too low. 



Lead (Determined Electrolttically). 



On account of tendency of lead and manganese to separate in the form 

 of peroxide at the positive pole, it was deemed advisable to make a series of 

 experiments on the metals themselves before attempting to effect their 

 separation. The results were as follows : 



Time. 

 Hours. 



16 



48 

 3 



16 



Difference 

 from theory. 



50 c.c. of a lead formate solution were used in each of the above experi- 

 ments. In all of them, the lead was deposited in a spongy state at the 

 kathode with more or less peroxide on the positive pole. 



As the moist metal deposited on the kathode rapidly oxidizes, even 

 when adherent and compact, the results obtained are invariably too high 

 and in practice it is customary to estimate lead as peroxide on the anode 

 securing its deposition in that form by the addition of nitric acid to the 

 solution. The results obtained with free formic acid, as given above, 

 w T ere not such as to justify attempting its separation from either copper, 

 cadmium or zinc. 



