THE FIXATION OF MERCURY 93 



attempts to grasp it ; it rolled about like a solid sphere, but 

 offered no resistance to the touch, and when pressed it split 

 up into innumerable smaller globules so that the problem 

 of " fixing " it must have had a strange fascination for the 

 thoughtful alchemist, especially when he found that, on 

 subjection to a comparatively moderate degree of heat, this 

 heavy metal disappeared in vapor and left not a trace behind. 



I have often wondered what the old alchemists would 

 have said if they had seen fluid mercury immersed in a 

 clear liquid and brought out in the form of a lump of solid, 

 bright metal. For, although this is not in any sense a so- 

 lution of the problem, yet it is a most curious sight and one 

 which was rarely seen before the discovery of the liquefac- 

 tion of the gases. To Geber, Basil Valentine, Van Helmont, 

 Helvetius, and men of their day, living in their climate, this 

 startling phenomenon would have seemed nothing short of 

 a miracle. 



In modern times the solidification of mercury had been 

 frequently witnessed by these who dwelt in northern cli- 

 mates and by the skilful use of certain freezing mixtures 

 made up of ordinary salts, it is not difficult to exhibit this 

 metal in the solid state at any time. But it was not until the 

 discovery of the liquefaction of carbonic acid, nitrous oxide, 

 and other gases by Faraday, about 1823, that the freezing 

 of mercury became a common lecture-room experiment. 



In the year 1862 the writer delivered a course of lectures 

 on chemistry, in the city of Rochester, N. Y., and during 

 the progress of these lectures he reduced carbonic acid first 

 to the liquid, and then to the solid state, in the form of a 

 white snow. The temperature of this snow was about 

 80 Cent. ( 1 76 Fahr.) and when it was mixed with 

 ether and laid on a quantity of mercury, the latter was 



