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 Front Page arrow Titles (by Subject) arrow CCXXIX: CONGELATION OF QUICKSILVER—COLD PRODUCED BY EVAPORATION 1 - The Works of Benjamin Franklin, Vol. III Letters and Misc. Writings 1753-1763

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CCXXIX: CONGELATION OF QUICKSILVER—COLD PRODUCED BY EVAPORATION 1 - Benjamin Franklin, The Works of Benjamin Franklin, Vol. III Letters and Misc. Writings 1753-1763 [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. III (Letters and Misc. Writings 1753-1763).

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CCXXIX

CONGELATION OF QUICKSILVER—COLD PRODUCED BY EVAPORATION1

Perth Amboy, 26 February, 1763.

The most remarkable discovery that has been made within these three years is, that quicksilver is in reality a melted metal, with this character only, that of all others it requires the least heat to melt it. The Academy of Sciences at Petersburg have found that by dipping a mercurial thermometer into repeated cooling mixtures, and so taking from the mercury the heat that was in it, they have brought it down some hundred degrees (the exact number I cannot remember) below the freezing point, when the mercury became solid and would sink no longer, and then the glass being broke it came out in the form of a silver bullet adhering to a wire, which was the slender part that had been in the tube. Upon trial it was found malleable, and was hammered out to the bigness of a half-crown, but soon after, on receiving a small degree of warmth, it returned gradually to its fluid state again. This experiment was repeated by several members of that Academy two winters successively, and an authentic account of it transmitted to our Royal Society.

I suppose you have seen in the second volume of the new Philosophical Essays of the Edinburgh Society an account of some experiments to produce cold by evaporation, made by Dr. Cullen, who mentions the like having been before made at Petersburg. I think it is but lately that our European philosophers have known or acknowledged any thing of such a power in nature. But I find it has been long known in the east. Bernier, in the account of his travels in India, written above a hundred years since, mentions the custom of travellers carrying their water in flasks covered with wet wrappers, and hung to the pommels of their saddles, so as that the wind might act upon them, and so cool the water. I have also seen a kind of jar for cooling water, made of potter’s earth glazed, and so porous that the water gradually oozed through to the surface, supplying water just sufficient for a constant evaporation. I tried it, and found the water within much cooler in a few hours. This jar was brought from Egypt.

[1 ]This is a fragment of a letter in the handwriting of Franklin, but it is not known to whom it was written.