1870.] Physics. 137 



attention of chemists, and various means have been proposed for its 

 prevention. Dr. Hugo Miiller, F.K.S., has described a ready means 

 for overcoming this annoyance. In cases where the introduction of 

 any foreign matter into the liquid about to be distilled is undesir- 

 able, he indroduces through the cork in the tubulus of the retort a 

 glass tube, which is drawn out to a long capillary tube, and pressed 

 tightly to the bottom of the retort. The upper end of the glass 

 tube is connected by means of an india-rubber tube, with a generator 

 of carbonic acid or hydrogen, or a gas-holder containing air ; and 

 whilst the distillation is going on, one of these gases is passed in a 

 slow but continuous current through the liquid. Under these 

 conditions all bumping is avoided, and the distillation proceeds with 

 the utmost facility. For ordinary purposes, however, it is still 

 more convenient to introduce into the liquid about to be distilled a 

 small fragment of sodium amalgam, or, in cases where the liquid is 

 acid, a small piece of sodium- tin. Methylic alcohol is well known 

 to be one of the most difficult liquids to distil, yet on the intro- 

 duction of a minute piece of sodium amalgam or sodium tin it can 

 be distilled without the slightest inconvenience. The action of 

 sodium amalgam and sodium- tin is due to a minute but continuous 

 disengagement of hydrogen taking place during the process of 

 distillation. 



Dr. Hofmann has described an ingenious experiment to show 

 that a body really increases in weight during combustion. A small 

 horse-shoe magnet is hung up at the beam of a balance, sufficiently 

 sensitive to turn with centigrammes ; the poles of the magnet are 

 immersed for a moment in levigated iron, when a beard of small 

 particles of iron adheres to the poles ; by means of proper weights 

 placed on the scale-pan at the other end of the beam the equilibrium 

 is restored. This having been done, the finely-divided iron is 

 kindled by approaching to it the flame of a Bunsen gas-burner, and 

 continues to burn. While burning, it will be seen that the arm of 

 the balance on which the magnet is suspended considerably deviates 

 from the horizontal position, thus indicating an increase of weight 

 on the side where the experiment is going on. This experiment 

 succeeds best with a magnet of moderate dimensions. The horse- 

 shoe magnet applied in this instance weighed without its armature 

 210 grms., and can bear a load of 12 • 5 grms. of iron. When this 

 is altogether converted in magnetic oxide by combustion the increase 

 in weight will be about 4 * 7 grms. 



Dr. Seelhorst has repeated Barrett's well-known experiments of 

 holding in the flame of burning hydrogen gas very well-cleaned 

 glass rods, metals recently cleaned by filing them just previous to 

 the holding in the flame, and has observed the same blue coloura- 

 tion as Mr. Barrett did. But the author is not inclined to ascribe 



