458 Mr. T. H . Henry on a New Compound of Gold and Mercury. 



which he explains thus : — " As the luminous effects are undoubt- 

 edly owing to a vibratory movement executed by the molecules 

 of the platinum, it seems from the foregoing considerations to 

 follow, that the frequency of those vibrations increases with the 

 temperature." 



Sir David Brewster has observed, that in the spectra produced 

 by the electric light the chemical rays are more numerous than 

 in those produced by the lime light. 



The problem then to be solved is, — whether the chemical rays 

 be produced directly by the oscillations of the electrical aether in 

 the platinum wire, or indirectly by the heat produced. 



This question might be resolved by observing the effect pro- 

 duced by voltaic piles of different intensities, the heat remaining 

 constant ; and if so, it would afford a strong argument in favour, 

 not only of an oscillatory movement in the electrical aether in 

 combination with the particles of bodies, but also of the existence 

 of such an aether through space. 



I have the honour to be, Gentlemen, 



Your obedient Servant, 



George James Knox. 



2 Fiochley New Road, St. John's Wood, 

 May 3, 1855. 



LXV. On a New Compound of Gold and Mercury. 

 By T. H. Henry, Esq., F.R.S.* 



WHEN gold is treated with mercury in large excess, a defi- 

 nite compound is formed which remains dissolved in the 

 mercury, from which, however, it often separates in a crystalline 

 form, and from which it may be almost entirely separated by 

 mechanical means, such as pressure through chamois-leather. 

 This solid amalgam crystallizes in four-sided prisms, and con- 

 tains six parts of gold to one of mercury, and fuses on elevating 

 the temperature (Gmelin, vol. iii.). The mercury, however, 

 which has passed through the chamois-leather always contains 

 gold, in proportion varying from a minute trace to 10 grs. in 

 the pound. In the metallurgical pi-ocesses for extracting gold, 

 it becomes important to estimate the amount of gold remaining 

 in the fluid part of the mercury, and it was during some experi- 

 ments made with the view of ascertaining the best method of 

 doing so that this new amalgam was discovered. 



This substance is best obtained by dissolving gold in mercury 

 in the proportion of 1 part of gold to 1000 of mercury, about 

 7 grs. to the lb. avoirdupois, squeezing the solution through 



* Communicated by the Author. 



