Faraday to Benjamin Abbott   1, 2 and 4 September 1812

Sept. 1st. 1812.

Dear Obliging Abbott,

I acknowledge the receipt of you last letter dated Aug 28th and intend to preserve it sacredly not only as a part of our correspondence but as a proof of your kindness & industry. I am sorry & beg pardon of you for reproaching you not knowing your situation and promise not to offend so again - I condole with you most sincerely on account of your indisposition - I am surprised and that not agreeably at its remaining on you so long - Your situation (for the view of which I thank you) is certainly not the most agreeable it is almost pitiable but I conceive it will not last long and then all will be right again nevertheless in order to support you by giving you a little relaxation and bringing to your mind other objects I will again take up the subject of Chlorine & back the opinion I conceive to be correct and have affirmed by experiments & reasonings in the best manner I can.

In my last if I remember rightly I gave as proofs that Chlorine gas contained no Oxygen experiments in the following import - That the Carbonaceous part of a taper would not burn in it - That ignited Carbon or Charcoal would not burn in it - That when Chlorine and Hydrogen were united no results containing Oxygen appeared - That when Steam & Chlorine were made to act on each other all the Oxygen obtained came from the water and as a proof that Muriatic Acid is a compound I noticed an experiment in which it is decomposed by Potassium the chlorine being taken from it by the metal & I slightly adverted to the peculiar combinations of other metals & Chlorine.

It was necessary dear Abbott that I should thus recapitulate what I had before said on this subject for so many things have since engaged my attention and draw it off from that point that it was essential to re-collect my thoughts again to avoid saying largely now what I had said before. Sept. 2. - (Last night dear A<_> I saw you and heard some of your objections but shall not answer them untill I have them in writing thus then I proceed).

At this time my arguments in favour of the simplicity of Chlorine will be drawn from the nature of the results when it pure is made the supporter of combustion and when it is combined with other bodies - I have already observed one of these combinations i.e. when Hydrogen was united to it - Hydrogen when united to Chlorine forms a pure unmixed uniform binary compound Muriatic Acid and no water is produced in weight too the weight of the Acid is exactly equal to the weight of its ingredients or rather components used[.] With Oxygen the other supporter of combustion it forms water a body very different to Muriatic Acid and different also are the combinations of the other inflammables with the two supporters.

Look into your Lavoisier into your Nicholson¹ into your Fourcroy² and what other Chemical books you have at the article Oxy-Muriatic Acid they will tell you that its Oxygen is held by an affinity so weak that the combustibles burn in it very easily and compounds of the Oxygen and inflamables are obtained as well as Muriatic Acid³ - You will think me bold dear A if I deny all these authorities but Davy has done so & I will do it too on the strength of his experiments[.] One has copied the errors of another & all are wrong.

As a proof of their want of experiments on this point and their abundance of assertions I will again tell you that Carbon has not yet been made to combine with Chlorine or if you please Oxygen of Oxy-Muriatic Acid it has not even apparently been made to do so that I know of and yet they affirm that all the combustibles burn in it and produce the same results as in oxygen gas[.] They were not acquainted with the peculiar fact of its non-combination but took it for granted that as it combined with Oxygen it would also burn in Chlorine - but these are a kind of negative facts tho very important ones let us now turn to the other combustibles[.]

Phosphorus I believe generally burns spontaneously in this gas with a pale flame and a solid compound is formed but not Phosphoric Acid tho that is solid too but a body very different from it[.] One essential character of PA is its great degree of fixedness it will not sublime or rise in vapour at an heat less than white ignition but this compound my good Sir is volatizable at an heat below 212° (I myself saw it rapidly rise from the heat of a small spirit lamp) and this is a very distinguishing difference let me tell you⁴[.]

The substance the Chloride of Phosphorus as we will call it combines with Ammonia⁵ - here I fancy I hear you crying out “an Acid an Acid it combines with an Alkali”!!! but softly my good Sir we have no Acid as yet - tho it does combine with Ammonia no Phosphat is formed but a dry powder[.] This powder is very different to the combination of PA & Ammonia and possesses different properties & characters[.] It is exceedingly fixed in the fire it will not rise at a white heat whereas the Phosphat of Ammonia is decomposed at an heat far below that point consequently it must be a different substance & Chlorine must be a simple body[.]

There is another compound of Phosphorous and Chlorine besides the foregoing which will afford some very strong proofs that Chlorine is a simple substance or rather that it is not & does not contain Oxygen[.] This compound is not in a solid form like the former but is a dense liquid it is obtained by distilling the Corrosive Sublimates of Mercury & Phosphorus together now what according to Lavoisier’s Theory would you suppose this liquid to be? Phosphoric Acid? or perhaps a mixture of Phosphoric & Muriatic Acids but no my good Sir either supposition would be wrong or any other that supposes an acid or Oxygen present[.] The liquid is no acid but a compound of Phosphorus & Chlorine it does not possess Acid properties[.] If a portion of it is dropped on to litmus paper or any other test paper for Acids it will cause no changes of colour except round the edges of the drops and that circumstance I will otherwise explain⁶[.]

Another proof that the Phosphorous exists in this compound uncombined with Oxygen is the following pour some of it on a surface as paper a film of Phosphorous will quickly form and if it is brought towards the fire it will inflame and burn it then combining with Oxygen a sufficient proof that it was not combined with it before⁷[.] What then was it combined with? Chlorine a substance containing no Oxygen but a simple supporter of Combustion.

This liquid compound is decomposed by & decomposes water⁸ & then Sir Abbott we have Acids in plenty If a portion of it is poured into a small quantity of water de- and re-combinations take place and a mixture of Phosphoric and Muriatic Acids are formed[.] During this or those actions no gas is evolved except it may be Muriatic Acid gas but no Oxygen or Hydrogen from the water is given out[.] They are both taken up in the re-compositions They are both necessary to form the Acids[.] The Oxygen of the Water unites to the Phosphorous and produces Phosphoric Acid[.] The Hydrogen unites to the Chlorine & forms Muriatic Acid and thus all the constituent parts are employed[.] The Hydrogen & Oxygen evolved from a certain portion of water is exactly sufficient to saturate both parts of a proper quantity of the compound of Phosphorus & Chlorine.

If now you apply it to the Litmus paper the effect of an acid immediately takes place because acids are present and yet it is diluted with thrice its quantity of water before when strong and concentrated it produced no effect on the test now by the addition of water it does a proof that there was no acid in it in the first case tho there was in the latter and a proof also that it was by the decomposition of the water the Acids were formed

I will now explain the reason of the change of colour observed when the compound was dropped on to Litmus paper it took place round the edges[.] The compound having so strong an affinity for water attracts it in a very effectual manner from the Atmosphere and forming such strong acids by its decomposition it immediately decomposed it and then the results acted on the paper now it is evident that this action of the compound would take place at the surface of the drop and as the only part where the surface touched the paper was round the edges it was there only that a change of colour could take place[.]

If you (as I suppose you do [)] still oppose this theory of Davy’s consider this experiment with care and account for it otherwise if you can[.] Remember that this compound of Chlorine & Phosphorus possesses not Acid properties[.] That the phosphorus in it will unite to Oxygen and therefore is not previously so that when poured into water it is not a dilution but an action a strong action that takes place and great heat is evolved[.] That both the Oxygen & the Hydrogen of the water is employed and - That then Acids are present[.] The Phosphoric Acid is readily accounted for it is produced by the union of the Phosphorus & the Oxygen but the Muriatic Acid how is that produced nothing but Chlorine & Hydrogen at present remaining nothing but these form that Acid, and nothing else is necessary.

There is a compound of Sulphur & Chlorine similar to the above described one of Phosphorus & Chlorine it is a red liquid & is obtained by heating sublimed Sulphur in Chlorine gas[.] This liquid like the former possess no Acid properties tho with water it forms two strong Acids Sulphuric & Muriatic[.] This decomposition of water by the compound is exactly similar in its action with the before mentioned one tho not in all its circumstances⁹[.] The Hydrogen liberated unites to the Chlorine & the result is muriatic Acid[.] The Oxygen unites to the Sulphur & forms sulphuric Acid but it so happens that the quantity of Sulphur in the compound is greater than can be saturated by the liberated Oxygen[.] If we conceive a certain portion of the compound to be decomposed and also as much water as will afford Hydrogen sufficient to combine with all the Chlorine of the compound then the Sulphur separated from that quantity is far too much for the Oxygen liberated from the decomposed water consequently Sulphur is separated & remains pure[.]

I have thus dear Abbott detailed the principle facts that I am acquainted with respecting the reciprocal action of the inflamables and Chlorine[.] They all of them afford convincing proof that Chlorine is as yet an undecomposed body & Sulphur & Phosphorus combine with it in the first in one proportion & the second in two[.] These three compounds are new & singular ones and exhibit very curious Phenomena[.] They are not neither do they contain any acid - Carbon will will not or at least has not yet been made to combine with Chlorine a striking proof that it contains no oxygen - Hydrogen unites to it and is the only one of the combustibles that forms with it an Acid namely the Muriatic Acid - In my next I will continue the subject but positively will first hear from you so that I may know my opponent & his objections.

Adieu, dear Ab<<bott>> | M. Faraday

Sept 4. Friday evening received of Mr. B. Abbott the sum of 24 lines contained in a letter dated Sept 3, 1812[.] Is any [word illegible] by me MF. | MF congratulates Mr. A on his acquisition of Accum ¹⁰ and thinks he has made a good bargain he will enquire about the Phosphorus shortly & thanks Mr. A<_> for his promise of a letter & experiments and expects them impatiently and to conclude he will be exceedingly obliged to him for Admission to Mr. J. Tatum’s lecture on the Alkalies he of course even hopes of seeing Mr. Abbott that evening and till then remains Mr. A

Obedient Humble Servant | M. Faraday | Ha. Ha. Ha. Hah!!!¹¹

Address: Mr. B. Abbott | Long Lane | Bermondsey