Faraday to Christopher Haedy¹   15 December 1831

Royal Institution | Dec. 15, 1831.

Dear Sir

Having received the pipes the sediment and the waters I have been engaged in examining them[.] The sediment is not altogether white lead but is a mixture of carbonate and sulphate of lead. It is of course due to the conversion of the lead by the water and air as if it had all been carbonate, but the mixed nature influences a little the reasoning upon the subject.

The copious incrustation of the pipe which I took away is also a mixed carbonate and sulphate of lead. I have no doubt the extreme action upon the pipe compared to the action upon the cistern in which it stood has been due to a slight difference in the quality of the two leads which has determined a voltaic action.

With regard to the water from over the deposit, when it had become quite clear by standing it then contained no lead & was perfectly wholesome[.] But if shaken up with the deposit & taken after wards whilst in a turbid state it contained lead in the diffused state and in that state would be unwholesome. It is therefore a matter of importance to know whether under the arrangement made of the cisterns any or how much of the water is used whilst it is in a turbid state from the agitation due to pumping it from the well into the cistern[.]

Respecting the water from the well, it is a very good water. It contains very little earthy salt but muriate of soda[,] sulphate of lime a little & a little carbonate probably of soda. I do not think any thing you can do to it will remedy the evil[.]

The person who brought me the articles told me a plumber had mentioned to him the application of tallow to the lead. It reminds me of other experiments & results relative to the penetration & preparation of metals by oils & fats. I have known the application of tallow & oil to brass & iron distinctly cause a degree of preservation and if the cisterns at the Market² were mine I should do as follows. I would wash clean & dry out the cistern – then mix one part of tallow with one part of bees wax – make it hot – then with one of those fire places at the end of a pole which fishermen use when they tar their boats I would dry & warm the lead (inside of course) & brush it over with the heated mixture and finally melt it by the heat of the fire again upon the lead[.] The object is not to put a thick coat upon the metal but to do every part when perfectly dry well over: The excess may run down and I do not believe that even wiping the lead with a dry cloth would injure but that a thin coat should be left every where[.]

I am Dear Sir | Yours very faithfully | M. Faraday - Haedy Esq | &c &c