Letter from Michael Faraday to Frederick Pollock

Royal Institution
Albemarle Street
Friday March 19th [1824]

My dear Sir

I am afraid I shall give you but a bad account
of the gases for I have but a few moments to spare. I think
I sent you a copy of the paper at least I hope so for I have
none left. However you will have it in your Transactions.

Nine gases gave way before the attempts I made to in-
duce them these are - Sulphurous acid - Sulphuretted hy-
drogen - Carbonic acid - Euchlorine – Nitrous oxide - Cyanogen –
Ammonia - Muriatic acid – Chlorine

S.G. [Specific Gravity]
Sulphurous acid – 1.42 [S.G.] - 2 atmospheres at 45 [degrees] F
Sulphur[etted] hydrogen – 0.9 [S.G.] – 17 [atmospheres] - at 50 [degrees]
Carbonic acid - - [S.G.] - 36 [atmospheres] - at 32 [degrees]
Euchlorine - - [S.G.] - - [atmospheres] - -
Nitrous oxide - - [S.G.] - 50 [atmospheres] – at 45 [degrees]
Cyanogen – 0.9 [S.G.] – 3.6 [atmospheres] – at 45 [degrees]
Ammonia – 0.76 [S.G.] – 6.5 [atmospheres] – at 50 [degrees]
Muriatic acid - - [S.G.] – 40 [atmospheres] – at 50 [degrees]
Chlorine – 1.33 [S.G.] – 4 [atmospheres] – at 60 [degrees]

Your question with regard to carbonic acid is answered
above. Of course the pressure of all these bodies increases
with any increases of temperature and in consequence of
the expansive power of some of them I have had several
explosions and some wounds.

I perceive you wish to know the greatest pressure
I have used. The nitrous oxide as you will perceive
acquires a pressure of 50 atmospheres at 45 [degrees] and during
the process by which it is liberated which consists in heating
a closed tube containing nitrate of ammonia up to 300 [degrees] –
350 [degrees] F. The pressure within [?] have been less I think
at times than 100 atmospheres probably much more.

I fancy I perceive a hint in your note at a vapour
or gas engine – but of this we will say nothing. If such a
thing is made (and there is no want of power) you shall know
of it immediately: be assured that all proper attention is
given to this point but as it is wiser to not to talk
of expected results, than to talk of fact we will in this
not initiate our friend of Fleet Street.

I was assured the other day at the House of Commons
(on a Committee) by Your Brother – Not long since
I was called upon for an opinion in a Committee on the
comparative advantages of oil and coal gas. Mr David Pollock
strongly examined me against coal gas. A day or two after
a bill of a member bound for another place was before a committee
and he had to be just as anxious for oil gas as he had
before been for coal gas – I know that this is nothing to
you but it is very amusing to me.

Ever Been [?] for

Yours Very Truly

M Faraday

Fred[erick] Pollock Esq