120 
MR. DANIELL ON VOLTAIC COMBINATIONS. 
purpose, 4^ measures of oil of vitriol to 100 measures of water, sp. gr. 1056*2, and 
found the mean quantity of gas evolved in the voltameter increased to 3*8 cubic 
inches per five minutes. I then removed the meter, and connected the circuit, leaving 
the battery in action for four hours. Upon replacing the meter it was ascertained to 
be still working at the same rate. The addition of nitric acid to the solution of the 
sulphate again reduced the rate to 2*1 cubic inches. 
I now made trial of an addition of nitric acid to the interior liquid of the cell, 
adding an equal volume to that of the sulphuric acid, and restoring the solution of 
the neutral sulphate to the exterior division. At the first impression, an increased 
effect seemed to be produced, and the action for the first quarter of an hour was as 
high as 4*2 cubic inches per five minutes ; but it ultimately settled down, and remained 
at the former amount without the nitric acid, of 3*8 cubic inches. 
Here I may remark, that at the first immersion of the rods the effect of the battery 
is always a little higher than it afterwards settles at : and this I found to depend upon 
the evolution of a small quantity of hydrogen from a residue of local action upon the 
zinc, which adhered to its surface, and slightly impeded the action of the acid. These 
bubbles scarcely ever rose to the surface, and after the first quarter of an hour the 
battery took up a steady rate of action. By gently agitating the rods in the acid, the 
action Avould momentarily return to its original amount, but always settled down to 
the lower rate. 
How very small this local action is will be seen from the details of the following 
series of experiments, which I shall give at length. Upon this occasion I weighed 
the ten zinc rods, which were the same which I had us;ed from the first, and were re- 
duced to nearly half their original circumference, that I might judge how nearly the 
zinc oxidated would be equivalent to the volume of gases evolved : their weight was 
2^ lbs. and 13 grains (15,763 grains). I trebled the strength of the acid, adding 6f 
measures of oil of vitriol to 100 measures of water, sp.gr. 1079*4. I sometimes made 
use of a large voltameter, the plates of which were 3 inches by 1 inch, and which, 
having a bent tube, admitted of my receiving the gases into a large graduated jar, 
and sometimes of the same small meter which I had hitherto employed. The results 
are contained in the following Table. 
