The rush of water necessarily produced by an intermittent flow must also detach portions of carbonate of lead from the sides of the pipe, even in those cases where the water has no very decided action on lead, and it is therefore far from improbable that in this manner the poison of lead is occasionally conveyed into our kitchens, and becomes mixed with our food.
According to your desire, I have examined the action of the waters from the above-mentioned sources on clean lead, and have arrived at the following conclusions:—the water from Haslemere has a slow though decided action upon the metal, no effect taking place until the lead had been partially immersed for four or five days. After that time, a small deposit of carbonate of lead was perceptible at the bottom of the vessel, although none could be detected in solution. The absence of carbonic acid in the water from Haslemere, Boorley, and Barford, would in all probability prevent their acting upon lead, were atmospheric air at the same time excluded. A piece of lead that had been kept for a week in a closed bottle filled with water from Haslemere did not exhibit the least trace of carbonate of lead, nor could the presence of lead be detected in the water.
It is scarcely necessary to add, that the water as drawn from the pipes of the New River and East London Companies does not exhibit the least solvent action upon lead; when, however, purified by boiling, and placed in contact with lead, crystals of carbonate of lead were observable after the lapse of three days in the water of the New River Company, while, owing to its greater hardness, the water of the East London Company did not exhibit any traces of carbonate of lead until the expiration of more than a week, and even then only in a slight degree. The same waters purified by the patented process of Clark did not exhibit so decided an action upon lead as when purified by boiling; but after evaporating to dryness the water in which lead had been immersed for three weeks, and dissolving the residue in dilute nitric acid, the presence of a minute quantity of lead was rendered evident.
It therefore appears that if leaden pipes, and especially if leaden cisterns, are to be employed in the distribution and storage of water, on the system of interrupted supply, it will be a necessary safeguard, that the water thus conveyed and stored should not be of less hardness than from six to seven degrees, compared with distilled water as unity; and conversely, it also follows, that if the inhabitants of the metropolis are to gain the advantage of using a still purer and softer water, it will be requisite to do away with the existing leaden pipes and cisterns, and to substitute for them some material which shall not communicate any poisonous or noxious ingredient to the water. As matters now stand, we escape daily poisoning by the use of water loaded with earthy salts, and are thus compelled to drink an impure water on account of the impurity of our vessels. Would it not be better, and is it impossible, to drink the pure element from a pure cup?
I remain, dear sir, with much respect,
Yours obediently,
Thomas Taylor.
To John Simon, Esq., F.R.S.,
Officer of Health to the City of London.
THIRD ANNUAL REPORT.
November 25th, 1851.
Gentlemen,