ON THE EXTRICATION OF THE ALKALIFIABLE METALS, 37 



In this lies the great difficulty of obtaining any available quantity of the 

 radicals of the alkaline earths by electrolization ; especially in the case of cal- 

 cium. It is easy, by a series of only fifty pairs, to produce an amalgam with 

 that metal, which, when exposed to the air, will become covered with a pul- 

 verulent mixture of lime and mercury; but, in such case, the quantity of cal- 

 cium taken up by the mercury, when estimated by the resulting oxide, will be 

 found almost too small to be appreciated by weighing. To increase the quan- 

 tity of calcium to an available extent I have found extremely difficult, since, 

 as the process proceeds, the chemical affinity becomes more active while the 

 electrolyzing power becomes more feeble. 



That a change should be effected in mercury, giving to it the characteristics 

 of an amalgam, by the addition of a six hundredth part of its weight, cannot be 

 deemed difficult to believe, when it is recollected that Davy found that when, by 

 amalgamation with ammonium, a globule of mercury had expanded to five times 

 its previous bulk, it had gained, in weight, only one twelve thousandth part. * 



As the affinity between the chlorine and the radicals of the alkaline earths 

 increases in strength with the temperature, and as heat is evolved in propor- 

 tion to the energy of the voltaic action, the disposition of the elements sepa- 

 rated by electrolyzation to reunite is, in this way, promoted. Hence the 

 necessity of refrigeration. 



The best index of the success of this process is the evolution of chlorine; 

 since in proportion to the quantity of this principle extricated at the anode, 

 must be the quantity of calcium separated at the cathode. During my opera- 

 tions, chlorine was evolved so copiously as to tinge the cavity of the innermost 

 bell with its well known hue. Hence, when the evolution of chlorine ceases 

 to be very perceptible, the amalgam should be extricated from the apparatus, 

 and separated by a funnel and the finger from the solution of chloride, and 

 immediately subjected to distillation. 



It has been mentioned, that in the electrolytic process above described I 

 resorted to the alternate action of two deflagrators. This was effected by 

 making the negative poles of both communicate with the mercury in capsule 

 D, while the positive poles communicated with some mercury in capsule L. 

 For a description of the deflagrators employed, I refer to the American Philo- 



* See Tilloch's Magazine, vol. xxxiii. p. 213. 

 VII. K 



