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CCCCXLIV: FROM JOSEPH PRIESTLEY TO B. FRANKLIN - Benjamin Franklin, The Works of Benjamin Franklin, Vol. V Letters and Misc. Writings 1768-1772 [1904]

Edition used:

The Works of Benjamin Franklin, including the Private as well as the Official and Scientific Correspondence, together with the Unmutilated and Correct Version of the Autobiography, compiled and edited by John Bigelow (New York: G.P. Putnam’s Sons, 1904). The Federal Edition in 12 volumes. Vol. V (Letters and Misc. Writings 1768-1772).

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CCCCXLIV

FROM JOSEPH PRIESTLEY TO B. FRANKLIN

Leeds, 1 July, 1772.

Dear Sir:—

I presume that by this time you are arrived in London, and I am willing to take the first opportunity of informing you that I have never been so busy, or so successful in making experiments, as since I had the pleasure of seeing you at Leeds.

I have fully satisfied myself that air, rendered in the highest degree noxious by breathing, is restored by sprigs of mint growing in it. You will probably remember the flourishing state in which you saw one of my plants. I put a mouse in the air in which it was growing on the Saturday after you went away, which was seven days after it was put in, and it continued in it five minutes without showing any sign of uneasiness, and was taken out quite strong and vigorous, when a mouse died after being not two seconds in a part of the same original quantity of air, which had stood in the same exposure without a plant in it. The same mouse, also, that lived so well in the restored air, was barely recoverable after being not more than one second in the other. I have also had another instance of a mouse living fourteen minutes without being at all hurt in little more than two ounce measures of another quantity of noxious air, in which a plant had grown.

I have completely ascertained the restoration of air, in which tallow or wax candles, spirit of wine, or brimstone-matches, have burned out by the same means.

The nitrous air, which I showed you, I found to be an admirable test of air that is fit for breathing. It makes this air red and turbid, but no other that I have tried. I took air, in which a mouse had putrified, which was in the highest degree noxious and fetid, and also a quantity of fixed air. The nitrous air, admitted to each of these kinds of air separately, made no sensible alteration in them; but, when they were mixed (which I discovered to make a wholesome air), the nitrous air made the mixture turbid and diminished the bulk of it, as in common air, though not in the same degree. A mouse put into this mixture lived five minutes without uneasiness, when, if it had been put into either of them separately a few minutes before, it would have died in a few seconds.

Air that has passed through hot charcoal has many, perhaps all the properties of air that has been diminished by other processes. It extinguishes flame, kills animals, and is not diminished or made turbid by a mixture of nitrous air.

But the observation, that pleases me more than any I ever made, is the diminution of air by the crystallization (I believe) of quicksilver and the nitrous acid. This effect both precedes and follows the generation of nitrous air from the same mixture. This I suspect to be the case with other crystallizations.

I have observed many other things, which I have not room to mention at present.

I am, with great respect, dear Sir,
Yours sincerely,

Joseph Priestley.