BARIUM, STRONTIUM, AND CALCIUM. 33 



a complete decomposition was extremely difficult, since nearly a red heat was 

 required, and that at a red heat the bases of the earths acted upon the glass, 

 and became oxygenated. When the tube was large in proportion to the quan- 

 tity of amalgam, the vapour of naphtha furnished oxygen sufficient to destroy 

 a part of the bases ; and when a small tube was employed, it was difficult to 

 heat the part used as a retort sufficiently to drive the whole of the mercury from 

 the base without raising too highly the temperature of the part serving for a 

 receiver so as to burst the tube." " When the quantity of amalgam was about 

 fifty or sixty grains, I found that the tube could not be conveniently less than 

 one-sixth of an inch in diameter, and of the capacity of about half a cubic inch. 

 In consequence of these difficulties, in a multitude of trials I had few success- 

 ful results; and in no case could I be absolutely certain that there was not a 

 minute portion of mercury still in combination with the metals of the earths."* 



The observations are more than confirmed by my experience, which leads 

 me to the conviction that the removal of the mercury is not to be accomplished 

 thoroughly in glass vessels, and, of course, that Davy was perfectly correct in 

 supposing that the products which he described as barium and strontium were 

 alloys with mercury. I am also under the impression that the metals above 

 mentioned decompose naphtha, when heated with its vapour, and enter into 

 combination with its constituents. Had the barium which Davy obtained 

 been free from mercury, it would not have been fusible below a red heat, as 

 alleged by him. Agreeably to my experience, that metal requires no less than 

 a good red heat for its fusion. 



In a subsequent paragraph he adds : " The metal from lime I have never 

 been able to examine exposed to air or under naphtha. In the case in which 

 I was enabled to distil the mercury from it to the greatest extent, the tube 

 unfortunately broke while warm, and at the same moment when the air entered 

 the metal, v/hich had the colour of silver, took fire and burnt, with an intense 

 white light, into quicklime."* 



Had the failure of Sir Humphrey, in his effi^rts to isolate calcium, been due 

 only to the accidental fracture of a glass tube, it would be inexplicable that a 

 chemist so indefatigable should not have successfully reiterated the experi- 



* See Transactions of the Koyal Society, part II. Nicholson's Journal, vol. xxi., for 1808; or, 

 Tilloch's Philosophical Magazine, vol. xxxiii. 

 VII. — I 



