Chemical Science. 379 



G. On the Preparation of Potassium and Sodium. — It is well 

 known to chemists, that the frequent failures in the preparation 

 of the alkaline metals arise from the high heat required in the 

 operation, which frequently fusing or cracking the lute on the 

 baiTel, exposes it to the air and fire, when it is soon burnt, and 

 the product either partly or entirely lost. The object of 

 M. Brunner, who is the author of the following experiments, 

 was to perform the operation at a comparatively low tempera- 

 ture, which he has been enabled to effect by the following 

 apparatus. 



The retort is a spheroidal iron bottle, about half an inch in 

 thickness, and capable of holding about a pint of water; a gun- 

 barrel bent into this form (P) screws into it at the shorter end. 

 When the retort is charged and luted, it is placed in a furnace, 

 so that the longer part of the bent gun-barrel may pass out at' 

 the bottom, or in front, in a direction nearly perpendicular, the 

 bent part itself remaining in the furnace ; and that it may be 

 protected from the fire, it is wound round with iron wire. The 

 receiver is a cylindrical copper vessel, with an opening at the 

 top to receive the end of the gun-barrel, and a tube passing 

 from the side to convey away the gas produced in the operation. 

 It is placed, when in use, in water or ice. 



The following is an instance of its use : the retort was cleaned, 

 dried, and heated, and then four ounces of fused caustic potash 

 introduced in small portions alternately with six ounces of 

 iron turnings broken in a mortar, mixed with one ounce of pul- 

 verized charcoal. The whole was stirred together, and covered 

 with two ounces of iron turnings. The retort being luted, the 

 barrel adapted, the whole placed in the furnace, and a glass 

 tube attached to the end of the barrel, that the progress of the 

 operation might be watched, the fire was lighted, and the heat 

 gradually raised: in ten minutes an inflammable gas came 

 over, which in ten minutes more burnt with a violet flame, pro- 

 ducing much fume; in ten minutes more the green vapours of 

 potassium appeared. The receiver containing naphtha was now 

 adapted, so that the end of the barrel should dip into the fluid ; 

 the liberation of gas was very rapid, and it frequently inflamed 

 spontaneously, burning with a white violet flame. In about 

 twenty-five minutes from the application of the receiver, the gas 

 diminished in quantity, and soon entirely ceased coming over; 

 the receiver was separated, and found to contain 150 grains of 

 potassium. 



Eight ounces of fused sub-carbonate of potash, 6 ounces of 

 iron filing, and 2 ounces of charcoal treated in the same way, 

 gave 140 grains of potassium. 



To ascertain the effect of the charcoal in these experiments, 

 3 ounces were mixed with 6 ounces of fused sub-carbonate of 



