Sixth Letter on Voltaic Combinations

J. F. Daniell
1842 Philosophical Transactions of the Royal Society of London  
My d e a r F a r a d a y , I MUST beg permission to address you once more upon the subject of Voltaic Com binations. To this I am prompted by several considerations. In the first place, the beautiful law of Ohm, and the simple expression which he has given of the electromotive force and resistances of a voltaic circuit, enable me to review with advantage, and to correct, many of the conclusions which I had derived from former experiments; and have suggested additional experiments, the results
more » ... ents, the results of which will tend, I trust, to remove some obscurities and ambiguities which were left in my former communications. 2nd. By following out these principles I shall be enabled to offer some practical remarks upon the different forms of voltaic batteries which have been brought for-* ward to assist the speculations of the active inquirers, who, in the present day, are so eagerly engaged in applying the voltaic forces to the service of the arts. 3rd. I wish most particularly to explain more fully the principles of the cylindri cal arrangements of the battery which I have introduced, and which appear to me to have been greatly misunderstood. I am desirous, however, that you should understand that I do not present the fol lowing observations for the purpose of testing the law in question, or of determining constants connected with the formula, for that could only be satisfactorily effected by experiments of a much more delicate and accurate nature than those to which I shall have to refer; but with a view to show how generally the law applies, even to the practi cal results of operations carried on upon, what might be called, a manufacturing scale, in which disturbing influences are numerous, and in a great measure uncontrolable. Professor Ohm has adopted (I believe that you will concur with me in thinking, m d c c c x l ii. t 138 PROFESSOR DANIELL ON VOLTAIC COMBINATIONS. unfortunately) the contact theory of the electromotive force ; and although his fo r mula is easily adapted to either of the two rival views, it is perhaps necessary, in selecting the chemical theory, that I should define the exact meaning which I attach to his symbols, and explain the expansions which I think it necessary to introduce. The formula, you will remember, is where E represents the electromotive force (so called) in the c e ll: R the resistances in the c e ll: r the amount of exterior resistances: A the effective force, measured by the work performed. Now according to the chemical view, E must be the balance of several active forces in the cell. 1st. The superior affinity of the generating plate for the , of the electrolyte, which we will designate by B. 2nd. The inferior affinity of the conducting plate for the spme which we will call b. 3rd. The affinity of the cation, disengaged from the electrolyte and accumulated upon the conducting plate for the anion, this we will call : these two last tend to produce polarization, as it is not very appropriately called, and a current in the op posite direction to B ; therefore
doi:10.1098/rstl.1842.0009 fatcat:gvqhk535pbe6jeaafcehmgiulu