1844.] of Bodies generally existing as Gases* 113 



The second column expresses the pressures given as the 

 fluid was raised from low to higher temperatures. The third 

 column shows the pressures given the next day with the same 

 tube after it had attained to and continued at the atmospheric 

 temperature for some hours. There is a difference of four or 

 five atmospheres between the two, showing that in the first 

 instance the previous low temperature had caused the solution 

 of a more volatile part in the less volatile and liquid portion, 

 and that the prolonged application of a higher temperature 

 during the night had gradually raised it again in vapour. This 

 result occurred again and again with the same specimen*. 



Cyanogen. This substance becomes a solid transparent 

 crystalline body, as Bunsen has already stated f, which raised 

 to the temperature of 30 Fahr. then liquefies. The solid 

 and liquid appear to be nearly of the same specific gravity, but 

 the solid is perhaps the denser of the two. 



The mixed solid and liquid substance yields a vapour of 

 rather less pressure than one atmosphere. In accordance 

 with this result, if the liquid be exposed to the air, it does not 

 freeze itself as carbonic acid does. 



The liquid tends to distil over and condense on the cap 

 cement and bitumen of the gauge, but only slightly. When 

 cyanogen is made from cyanide of mercury sealed up hermeti- 

 cally in a glass tube, the cyanogen distils back and condenses 

 in the paracyanic residue of the distillation ; but the pressure 

 of the vapour at common temperatures is still as great, or very 

 nearly so, as if -the cyanogen were in a clean separate liquid 

 state. 



A measured portion of liquid cyanogen was allowed to 

 escape and expand into gas. In this way one volume of liquid 

 at the temperature of 63 Fahr. gave 393*9 volumes of gas at 

 the same temperature and the barometric pressure of 3O2 

 inches. If 100 cubic inches of the gas be admitted to weigh 



* This substance is one of those which I liquefied in 1823 (see Philosophical 

 Transactions). Since writing the above, I perceive that M. Natterer has con- 

 densed it into the liquid state by the use of pumps only (see Comptes Rendus, 

 1844, Nov. 18, p. 1111), and obtained the liquid in considerable quantities. 

 The non-solidification of it by exposure to the air perfectly accords with my 

 own results. 



t Bibliotheque Universelle, 1839, xxiii, p. 184. 



I 



