AN ELECTRIC BATTERY FOR THE LABORATORY, ETC. 147 

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Neutral potassium oxalate 4oo gms. dissolved in a litre of 
boiling water, to which, when all is dissolved, is added 155 gms. 
of proto-sulphate of iron. The mixture is then to be set aside and 
preserved for use. 
When the solution is used, add to each 20 c.c. three or four 
drops of the following solution. 
One gramme of hypo-sulphite of soda in 200 gms. of water. 

AN EBELECTRIG BATTERY FOR 
THE LABORATORY AND DWELLING-HOUSE. 
By EmiLte REYNIER. 
T will, perhaps, be remembered by some that two years ago we 
proposed a zinc couple, soda-copper, sulphate of copper. This 
battery was as powerful as those in which nitric acid was used, and 
was free from emanations, while it required the manipulation of no 
acid at all. To make it suitable for domestic use it behoved us 
to reduce its cost, and we thought to arrive at this result by the 
electrolytic regeneration of the residues, but the great improve- 
ments made by M. C. Faure in the Planté accumulator came 
almost immediately to shew that the solution of the problem lies 
-in secondary batteries, the charge of the accumulators requiring no 
previous manipulation of the residues. 
The question of primary batteries remains none the less inter- 
esting on this account, as regards the convenient and independent 
production of the current ; moreover, accumulators, while supplant- 
ing primary batteries in their application to the distribution of 
energy, brought them as compensation a new element of success : 
the possibility of the production of the electricity beyond the hours 
during which it is required, in such a manner that it may be stored 
up and amplify the intensity of the electric energy during the 
discharge. 
A battery of small power can thus, by working without inter- 
ruption for twenty-four hours, generate the supply necessary for a 
more powerful but less prolonged discharge. 
Hence we see that certain voltaic contrivances, which have been 
set aside as not possessing sufficient energy, may be taken into use 
again, and in the first rank are the zinc couple, sulphate of zinc— 
copper, and sulphate of copper, which is very constant, quite in- 
odorous, and relatively economical. ; 
This cell, generally known under the name of the Daniell (though 
the principle of it was owing to Becquerel), had before received 
