Faraday to George Biddell Airy   31 October 1846

R Institution | 31 Octr. 1846

My dear Airy

To answer your question¹ exactly would require some experiment and a good deal of time i.e months: for the final relation of zinc & lead in ordinary water when both are jointly & voltaically subject to its action could only be ascertained after such long trial & when the metals with their investing coats had acquired a steady state.

I have however no confidence in the statement made for the following reasons. The abundant deposition on the zinc plate may be oxide of zinc instead of oxide of lead in which case the party who mistakes one for the other cannot be a very good adviser in the important affair which he enters into. Or if it be a deposition of lead salts, then it would seem to indicate that the zinc or Neg. & the lead Pos. which is just the reverse state to that which he thinks he produces - and finally the salts of lead cannot be deposited upon the zinc without the metal having first been dissolved in the water and such a continual deposition would prove therefore that the zinc had not prevented the presence of lead in the water and would suggest that perhaps it had increased it.

Ever Yours | M. Faraday

G.B. Airy Esq

Do not bring me into controversy. I have enough to do without it.