Faraday to John Frederic Daniell   29 October 1824

Royal Institution | Oct. 29 1824.

Dear Sir

I received a note from you dated last Monday¹ wishing me to examine the gases next week and send you an account thinking however a few days would make no great difference and not being quite sure you did not want them for this week I examined them this morning[.]

On looking at the small glass with hydrogen I found that the gas had increased in volume and on examining found it to be nothing but common air the mercury however was dirty & covered with a film and the experiment had not been put by with the particular care the tubes had received[.]

On examining the tubes themselves I could not perceive any change in the volume or appearance[.] I found that both contained a minute portion of oxygen which could be rendered evident by a platinum ball or by nitrous gas but the quantity was very minute apparently equal in the two tubes and I should think not more than the hydrogen contained at first[.]

I believe you know the date when the experiment was put on.

The following is an exact copy of my note of the experiments you wish described.

1823 June 26th. Made a mixture of 1 vol oxygen & 2 vols hydrogen - filled five dry bottles over mercury with the mixture and also 4 bottles over water - left them in glasses inverted over mercury and water having previously placed 3 mercury and 2 water bottles in the windows so as to receive the sun’s rays and day light and put the 2 mercury and 2 water bottles bye in a dark place.

Sept 3rd The mercury in the dry bottles is light black at the surface with thick film - one has a little moisture within[.] Opened one of the water bottles - was no expansion or contraction of volume 43 vols of gas came 10 vols of oxygen to nitrous gas[.] In consequence of evaporation the bottles have been left dry round the stoppers on the outside.

1824 July Examined the bottles - the water bottle in sunlight contained a little hydrogen and rest common air - no alteration of volume. The mercury bottle in light contained common air only. The water bottles in dark place - water right on the outside - no change in volume of gas - it was the original mixture - The mercury bottles in dark place contained nothing but common air. Hence mercury cannot confine gases perfectly - hence also no combustion in the dark nor (most probably) in the light either²[.]

In addition to these notes I may observe that the bottles were selected for the accuracy with which they had been stoppered and held about 4 ounces each that the stoppers were not greased or rather having been greased were then well wiped.

I am Dear Sir | Your obliged & faithful Servant | M. Faraday

J.F. Daniell Esq | &c &c

Address: John Frederick Daniell | West Humble | Dorking