Intelligence and Miscellaneous Articles. 463 



the friction against the barrel, taking the melting-point of lead as 

 335°, its specific heat as 0*031, and its latent heat of fusion as 5*37, 

 we find necessary 



For the heating 0*29 thermal unit. 



,, fusion 0*15 ,, 



For both together 0*44 „ 



From this calculation we see : — 



(1) That the mechanical theory of heat sufficiently accounts for 

 the operation. 



(2) Almost all the impetus of the motion of the body is trans- 

 formed into heat, — a result which was indeed to be expected, seeing 

 that the iron plate was very slightly deformed, and the projectile 

 rebounded but little. 



(3) By far the greater part of the heat was used in heating and 

 in melting the lead. This also is readily intelligible ; for the short 

 time within which the entire process was effected could give rise to 

 but little loss by conduction and radiation. — Poggendorff's Annalen, 

 No. 7, 1870. 



AN EXPERIMENT ON THE BOILING IN CONJUNCTION OF TWO 

 LIQUIDS WHICH DO NOT MIX. BY AUGUST KUNDT. 



Magnus *, and after him Regnaultf, have shown that the vapours 

 of liquids which do not mix obey Dalton's law of diffusion. The 

 common tension of the vapours of two non-miscible liquids (e. g. bi- 

 sulphide of carbon and water) in a state of saturation is equal to the 

 sum of the tensions which would correspond to the state of satura- 

 tion of the individual vapours for the temperature in question. Two 

 such liquids boil, therefore, when together, at a temperature which 

 is lower than the boiling-point of the most volatile. Magnus, how- 

 ever, in describing his experiments, remarks that the temperature of 

 the boiling liquid is somewhat higher than that of the most volatile 

 when the latter is underneath the less volatile one. 



Regnault remarks that in the boiling of two liquids which do not 

 mix it is very difficult to preserve constant temperatures in the vapour 

 and in the liquid ; the temperature varied materially with the heat- 

 ing and with the formation of bubbles. 



I have found that the anomaly observed by Magnus (that is, the 

 difference in temperature of the liquid and of the vapour) may be 

 completely avoided, and the experiment be so arranged that the 

 liquid during boiling retains exactly, and without variations, the 

 temperature which corresponds to Dalton's law. For this purpose 

 I do not heat the liquids, such as bisulphide of carbon and water, 

 together in a vessel by direct heat, but heat one by the vapour of 

 the other. Magnus once used this method to show that a concen- 

 trated saline solution can be heated by vapour from pure water to 

 the boiling-point of the solution in question % . 



The method is applicable both to miscible and to non-miscible 

 liquids. If into a vessel (and best of all a glass cylinder) which is 

 * Poggendorff's Annalen, vols, xxxviii. and xciii. 

 t Comptes Rendus,xo\. xxxix.; Relat. des Exper. vol. ii. 

 X Pogg. Ann. vol. lxi. p. 250. 



