Faraday to John Wilson Croker   9 June 1825

Royal Institution | June 9th. 1825

Sir

I have the honor of replying to your note and sending herewith the results of my examination of the samples of water &c¹. It is difficult to understand the case without having seen the state of the vessels and things about them but it seems to me that the observations and suggestions of Mr. Robertson² are of great importance and and apply directly to at least one of the causes of the impurity of the water[.]

It is not probable, hardly possible, that the water as it comes from the Well can contain any thing contributing in the slightest degree to the effect observed and indeed the presence of so much sulphuretted hydrogen gas and hydro sulphuretted oxide of Iron sufficiently proves that the impurity must be from some other source[.] The facility with which it could gain admission through the loose lids bathed as they are in water is very great and I cannot but think that some animal matter has found entrance in that way and caused much of the mischief[.]

The quantity of the sulphur present is very striking it may either have been introduced through the lids in connection with animal matter or it may have been derived from the joints of the tanks[.] Workmen are sometimes in the habit of using a cement for iron composed of Iron filings & sulphur which though it will when well made resist after a while the action of pure water might be affected by the results of putresence and in that way furnish sulphur[.]

With regard to the water in the casks I cannot understand why it should contain the hydrosulphuretted oxide of Iron unless it has been transferred into them from the tanks after putresence and the consequent action has been continued for some time and in that case the badness of the water in them should not be referred to circumstances connected with them alone[.] It is remarkable that the waters in the casks should contain free sulphuretted hydrogen whilst that in the tanks does not[.] Such water as is in the casks if transferred to tanks would gradually lose the free sulphuretted hydrogen and portions of the black deposit would be formed[.] Either therefore the casks and tanks have been filled with water in the first case putrescent & containing sulphuretted hydrogen or (as is suggested by the iron in the casks) the water in the tanks has become putred [sic] from the introduction of animal matter probably or vegetable matter sulphuretted hydrogen has been formed a portion of the water has in that state been put into the casks and remained comparatively unchanged whilst that remaining in the iron tanks has had its sulphuretted hydrogen combined with oxide of Iron as before stated[.] It is however impossible to give any thing like a strong opinion on the point without having examined the tanks casks water &c[.]

It is mentioned that oil was found floating on the surface of the water in some of the tanks a further proof that animal matter had in some way gained admittance[.]

I have the honor to be | Sir, | Your very obedient Humble Servant | M. Faraday

John Wilson Croker Esq | &c &c &c

Royal Institution | June. 9th. 1825.

Report on certain samples of water from tanks and casks on board His Majesty’s Ship Gloucester

No. 1 (Leager)

This water was dark in colour fetid and contained a black sediment. The water separated from the sediment was found to hold in solution small portions of muriate of soda very little of any sulphate and no earthy salts and therefore with regard to these substances which it would obtain from the earth was originally a very pure water. But it contained also a substance which when separated was similar to putrescent animal matter in its nature[.] It likewise held sulphuretted hydrogen in solution[.]

The black insoluble substance was a mixture of vegetable matter apparently and a hydrosulphuret of oxide or iron i.e a compound of sulphuretted hydrogen and oxide of Iron. It was not in large quantity[.]

No. 3. (Leager)

This water resembled No. 1 but was more fetid & contained more sulphuretted hydrogen[.] The salts were nearly in the same proportion and the putrescent substance also existed in it[.]

The sediment was similar in its nature to the last but contained much more destructible matter putrescent and resembling an animal substance[.]

No. 4 (Tank)

Water clearer than the former having no visible colour when freed from the sediment mixed with it but this sediment was very large in quantity[.] The odour of the water was slightly putrid but not of sulphuretted hydrogen nor did it contain any of that substance in a free state[.] Besides the salts before mentioned which the water contained in solution as good well water it also held iron in solution either by carbonic acid which was present or by carbonate of soda which had dissolved a portion of the hydrosulphuretted oxide of Iron (the black deposit). It contained a minute portion only of destructible or putrescent matter. It also contained carbonate of soda a constant accompaniment to the good water of the deep wells in and about London[.]

The sediment was almost entirely hydrosulphuret of oxide of Iron but contained a little decomposable matter[.]

No. 5 (Tank)

Water clear but containing very much black deposit in its nature precisely like the last. The odour of the water was bad and fetid but not like that of animal matter nor was any free sulphuretted hydrogen present. It was slightly chalybeate containing Iron in solution and probably as before the hydrosulphuret dissolved in Carbonate of Soda for the latter salt was present. But little matter capable of putrescence was present in the water and that appeared to be decidedly of a vegetable nature[.]

No.8. (Tank)

This water generally resembled the former tank waters except that it contained far more iron in solution and less as a deposit. The odour was bad but not animal in its nature nor was there any free sulphuretted hydrogen present. The water contained the usual salts in solution but with them so much iron as to make it excessively chalybeate all of which was held in solution as a hydrosulphuret by the carbonate of soda present.

The deposit was of a similar kind to the former containing with hydrosulphuret of oxide of Iron a little decayed vegetable matter.

The tough fetid membranaceous substance contained in the last bottle contains but little destructive matter though what there is is of a very putrescent kind[.] It is principally composed in mass of water and per oxide of Iron held together by a tissue composed of the matter already mentioned[.] When the iron was removed from a portion of it by an acid which was done without destroying the texture or form of the substance it became quite white and when dried resembled horn in its general appearance and in its products when burnt[.] It is a result of putrefactive processes but it is impossible when so far advanced to distinguish whether of animal or vegetable substances.

M. Faraday