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Note on the Vaporization of Mercury. By John Davy, M.D., 

 F.R.S., &c. Communicated by the Author. 



That mercury, at the ordinary temperature of the atmo- 

 sphere, like water, is capable of existing in the state of va- 

 pour, is, I believe, now admitted. A fact has lately come 

 under my observation, which, as an additional proof of this 

 property of the metal, may, perhaps, be deserving of record. 



In a press, from which light was excluded, and within 

 which there was very little circulation of air, a pneumatic 

 mercurial trough was kept, holding about 30 lbs. of quick- 

 silver, and also a bottle of iodine, closed, but not carefully, 

 with a glass stopper. The trough stood on an under shelf, 

 the bottle on an upper one, one over the other, about two 

 feet apart. After about two months that they had remained 

 undisturbed, at a temperature ranging between 50° and 55°, 

 having occasion to use the iodine, my attention was arrested 

 by an efflorescence, as it were, of a brilliant red colour, con- 

 sisting of minute crystals deposited on the upper rim of the 

 neck of the bottle, not on its under, and on the stopple above, 

 most abundant on the rim close to the stopper, gradually 

 diminishing towards its top. 



The red crystalline matter examined, was found to be bin- 

 iodide of mercury ; and as such, it is, of course, a proof that 

 the metal, as before said, is capable of passing into the state 

 of vapour at a comparatively low temperature. I did not 

 attempt to determine the quantity of the iodide formed ; from 

 its appearance, it may be conjectured to have been at least 

 one-tenth of a grain. 



It may be well for those who work much with mercury 

 to keep in mind this property, and guard against it, by car- 

 rying on their processes in well ventilated rooms. 



The Oaks, Ambleside, 

 May 9. 1845. 



VOL. XXXIX. NO. LXXVII. — JULY 1845. 



