158 Intelligence and Miscellaneous Articles. 



did not appear to rise beyond O m, 036 to m -03S at 69° F., and only 

 to m 020 to m 022 at 53°6 F., as appeared from the iodides of 

 mercury which were deposited upon the walls of the tube. In the 

 vaults of the observatory, it is true, the red iodide formed a very thin 

 ring, and this ring was only at a distance of a few millimetres from 

 the mercury ; this, which could not be foreseen from the previous 

 results, must be attributed to the moisture, the iodine tubes having 

 been fixed against the wall. In fifteen days, at a temperature of 

 72 0- 5 F. in the meridian chamber of the observatory, an amalgam of 

 silver gave rise to a much larger ring with vapour of iodine. This 

 ring was formed of very distinct crystals of determinable form ; it 

 was at m '015 from the amalgam. In most of the experiments with 

 iodine, the ring formed consisted of several iodides of the metal, but 

 the red crystallized iodide formed the greater portion, or existed alone 

 when the vapour of iodine being in slight excess, the experiment 

 was stopped at the proper time. By means of a tube of 1 metre in 

 length placed vertically in a larger tube resting upon mercury, John 

 Davy's experiment was verified, proving that iodine, placed at a 

 distance from mercury at the ordinary temperature, absorbs the 

 vapour of the latter. This agrees with the result furnished by vesi- 

 cular sulphur, and shows well that if the mercurial atmosphere ap- 

 pears to be limited when the iodine is in the state of vapour, this 

 arises solely from the circumstance, that the vapour of iodide of mer- 

 cury, and even that of iodine, have a considerable density compared 

 with the air. Hence it results that the vapour of mercury is repelled 

 to a certain limit which varies with the temperature, whilst the rings 

 formed by the iodides of mercury are at a tolerably constant height 

 at the same temperature. The vapour of bromine at ordinary tem- 

 peratures has the same action as that of iodine, as also the vapour of 

 turpentine and gaseous chlorine at 167° F. &c. 



Conclusions. 



1. Vapour of mercury appears to be subjects!, like other vapours, 

 to the law of mixture of gases and vapours, at all temperatures between 

 a few degrees below 32° F. and 86° F. ; and all the experiments 

 performed with sulphur in various states concur to show that the 

 limit set to the vaporization of mercury in consequence of the exclu- 

 sive employment of gold as a reagent, is exceeded beyond anything 

 that could have, been foreseen from Faraday's experiments, as it has 

 been ascertained that the vapour of mercury can rise to a height of 

 l m -76 at a constant temperature of 52 0, 7 F. 



2. If vapour of iodine, under certain circumstances, gives a result 

 which at first sight appears to indicate that vapour of mercury forms 

 a limited atmosphere, this appears to depend entirely upon the con- 

 siderable density, compared with the air, of the vapour of iodine and 

 of that of the iodide or iodides formed, and upon the slight volatility 

 of the latter. The same conclusion applies to vapour of bromine 

 and gaseous chlorine. 



3. On the other hand, the volatility of the product formed by the 

 combination of vapour of mercury with sulphur, and the very small 

 quantity of vapour of comparatively small density furnished by 8ul- 



