168 
IOWA ACADEMY OP SCIENCE 
We can now subtract the amount of sulphate combined with the iron and 
zinc from the total amount and the remainder will be the amount combined 
with hydrogen to form sulphuric acid. 
j = kl - m (4) 
given the amount of sulphuric acid; when k is the amount of available sul- 
phate, 1 the molecular weight of sulphuric acid, and m the molecular v/eight 
of sulphate. 
As v/e have the amount of sulphuric acid we can nov/ proceed to find the 
amount of nitric acid in the solution. As was said before this can be done 
by titration with a hydrate, but we must remember that the sulphuric acid 
will require some of the hydrate to neutralize it. I therefore subtracted the 
amount of potassium hydrate, as I used potassium hydrate for titration, re- 
quired to neutralize the sulphuric acid in the portion used. The remainder 
was the amount used in neutralizing the nitric acid. Methyl orange was used 
as an indicator as it changes color from the acid to neutral solution. The 
amount of nitric acid (N) is determined by the following formula: 
N = ACEd - Be (5) 
A is the molecular weight of nitric acid, B the molecular v/eight of potassium 
hydrate in one c. c., C the number of c. c. of potassium hydrate used against 
nitric acid, and d and e the same as in formula (1). 
We now have determined the amount of zinc sulphate or zinc, ferric sulphate 
or iron, sulphuric acid, and nitric acid in the depolarizer. The outer solution 
was much easier analyzed as it only contained sulphuric acid at first and later 
on zinc sulphate and sulphuric acid. I determined these the same way as I 
did in the depolarizer. 
In order to find the chemical action it was necessary to take out ten c. c. of 
both solutions every six hours and analyze it. This was done and the results 
are tabulated in data 3, 
A very essential thing to know about a cell is its action on open circuit. I 
let the cell stand for forty-eight hours on open circuit and the action was slight 
and much more in the zinc and sulphuric acid than on the nitric acid, there 
being 25.2 grams of zinc dissolved, 36 grams of sulphuric acid used and 1.4 
grams of nitric acid reduced. 
I took the E. M. P. of the cell by means of the Leeds Norturup potentia- 
meter, type K, and found it to be 1.8935. The next step was to find the internal 
resistance of the battery in order to know what external resistance would 
give a current of about nine amperes. The condenser method was used and 
the internal resistance B found by the formula: 
B = S(d'— d") - d" (6) 
Where S is the resistance in shunt, d" the throw on charge or discharge 
shunted, and d' the throw on charge or discharge. The throw is proportional 
to the voltage, and d' represents the E. M. P. and d" represents the P. D. with 
an external resistance S. Thus we see this method is only a simplified one of 
the regular fall of potential method, whose formula is: 
B = ( (E-V) -V) R or B equals (E-V) - C (7) 
I found the ohmic resistance to be .0710. I used the condenser method in finding 
the internal resistance on recovery and the fall of potential method when the 
battery was running on closed circuit. 
Having found the internal resistance (B) to be .0710, I used the formula: 
c = V (r b) 
