55 
cannot be completely exhausted, we will assume that each 
pound of zinc requires two pounds of sulphuric acid, in 
order to have the excess of acid which is requisite to main- 
tain a sufficiently powerful action ; adding the price of this to 
that of the zinc, we have about 8d. per pound, and the 
battery of 100 pairs as costing nearly 7d. per hour. 
If we take the modification known as Professor Daniel's 
battery, we have the intensity of 10 instead of 5.5 ; and 
5.5 X 100 = 10 X 55; and we therefore have to use 55 
pairs of elements instead of 100. Now the consumption of 
zinc in these will be 60 X 55 = 3,300, and should only 
cost about 3Jd. per hour for zinc and sulphuric acid to do 
the required work; but, in addition to these, we have sul- 
phate of copper consumed and metallic copper deposited. 
By my calculation, founded on the equivalent of copper 
and zinc, in 250 parts of sulphate of copper we have 16 
parts oxygen, 64 copper, 80 sulphuric acid, and 90 parts 
water. Now 64.6 parts of zinc are equivalent to 16 of 
oxygen. Therefore, as 64.6 is to 250 parts of sulphate 
of copper, so is 1 lb. of zinc to the required quantity of 
sulphate of copper, — 3.87 lbs. ; and taking 4d. as the price 
of sulphate of copper per lb., we must add to 8d., the cost 
of zinc and electrolite, 16d. (nearly) for sulphate of copper, 
making 2s. as the cost of electrolitizing the pound of zinc. 
The battery in question consumes 3,300 grains of zinc, and, 
therefore, costs about lid. per hour. The zinc will, how- 
ever, reduce the copper from its sulphate, producing a 
weight of copper nearly equivalent to that of the zinc, the 
value of which (if on a large scale) must be deducted. 
Taking the copper at lOd. per lb., we reduce the cost of 
working the battery to 6Jd. 
In calculating the expense of working a nitric acid bat- 
tery, I find that we cannot rely on the method of chemical 
equivalents; for when Grove's battery is worked in a close 
