On the Vapour of Mercury at common Temperatures. 57 



the liberation of carbon, as the perchloride does with the libera- 

 tion of chlorine, but we have not yet been able to ascertain that 

 point. We have only to offer as an apology for this and other 

 imperfections in the present paper, the smallness of the quan- 

 tity of this substance that we possessed. 



On the Vapour of Mercury at common Temperatures*. 



IT has long been admitted, that in the upper part of the baro- 

 meter and thermometer an atmosphere of mercury exists, even 

 at common temperatures, but having a very small degree of 

 tension. The following experiment renders it easy to show 

 this atmosphere even when the air has not, as in the instruments 

 above mentioned, been removed. A small portion of mercury 

 was put through a funnel into a clean dry bottle, capable of 

 holding about six ounces, and formed a stratum at the bottom 

 not one-eighth of an inch in thickness : particular care was taken 

 that none of the mercury should adhere to the upper part of 

 the inside of the bottle. A small piece of leaf-gold was then 

 attached to the under part of the stopper of the bottle, so 

 that when the stopper was put into its place, the leaf-gold was 

 enclosed in the bottle. It was then set aside in a safe place, 

 which happened to be both dark and cool, and left for between 

 six weeks and two months. At the end of that time it was ex- 

 amined, and the leaf-gold was found whitened by a quantity of 

 mercury, though every part of the bottle and mercury remained 

 apparently just as before. 



This experiment has been repeated several times, and always 

 with success. The utmost care was taken that mercury should 

 not get to the gold, except by passing through the atmosphere 

 of the bottle. I think therefore it proves, that at common 

 temperatures, and even when the air is present, mercury is 

 always surrounded by an atmosphere of the same substance. 



Experiments on the Alloys of Steel, made with a View to its 



Improvement. By STODART and FARADAY f 

 IN proposing a series of experiments on the alloys of iron and 

 steel with various other metals, the object in view was twofold: 



* Quarterly Journal of Science, x. 354. f Ibid. ix. 319. 



