Faraday to John Fox Burgoyne   7 October 1859¹

Royal Institution, 7th Oct., 1859.

My dear Sir John,

I consider your request relating to the leaded water an honour, and in replying may add an observation or two to the original matter². The case at first was simply that of certain waters, which, having been collected from rain by roofs, gutters, pipes, or cisterns of lead, were contaminated more or less with the metal. All water so obtained has not been found thus affected, and there is much difference and uncertainty about the mutual action of lead and water in different cases. When rain water falls upon surfaces of lead it is apt to act on them, and the water thus contaminated, by standing exposed to air, generally clears itself from the dissolved lead, the metal separating as a carbonated precipitate, and falling to the bottom. But when the sea-spray has access to the leaded surfaces, the action of the rain water is such that the dissolved lead does not separate in this way, or if it does, only after a much longer time. It is such water as this that I recommend to be treated with carbonate of lime. Enough whitening or levigated chalk is to be mixed with the fluid to make it of the consistency of good milk (though more will do no harm), and the whole is either to be filtered or to stand until clear. I have never yet found any sample of water poisoned as above that was not freed from the lead by this process; and from the actions that occur in the laboratory I have no doubt that if two or three pounds of such powdered chalk were put into a cistern, and stirred up occasionally after rain, it would keep the water free from lead.

Now my consideration was entirely confined to cases of the above kind, and to the service of the Trinity House. I might say much more to you about the modes of testing for lead in water, so as to discover its presence, and, within certain limits, its proportion, and also about the clearance of lead from all domestic waters by filtration or otherwise, but I have always found that chemical practice was required to make such knowledge available, and that for that reason it was nearly useless in the hands of the public. When, too, a particular case becomes mixed up with the numerous cases that may be associated with it, I think it often disappears from view, and the whole are after a time forgotten. Hence I prefer adhering to the case of adulteration arising from the joint action of salt water, or sea spray, and lead; and I have the full confidence that if it arise at any of your military posts at home or abroad, no difficulty will be found in the effective application of the remedy.

I am, | My dear Sir John, | Your very faithful servant, | M. Faraday

To Sir J.F. Burgoyne | &c., &c., &c.