148 Mr. Carl Barns mi the Pressure-Variations of 



Accordingly I was not surprised to find that the tempera- 

 tures obtained in the static method by Regnault, Hagen, 

 Hertz, Ramsay and Young*, are as a rule decidedly below the 

 corresponding boiling-points of the present dynamic method. 

 It is only by taking great pains in the adjustment of burner 

 and apparatus, that my temperatures began to coincide with 

 those of Regnault. But this nice adjustment introduces 

 arbitrary conditions; hence the low-pressure boiling-points 

 of mercury are to be rejected. At high pressures the un- 

 satisfactory circumstances mentioned fall away, and the rate 

 at which boiling-point changes with pressure is very much 

 reduced. Fig. 3, § 15,. will show the difficulties which I 

 strove to overcome ; but as my data, even in the final work, 

 are not of exceptional accuracy, I will omit them here. 



7. The behaviour of sulphur is peculiar. On removing 

 pressure to about 1 centim., the substance passes into the 

 treacle state, and the full ebullition observed under atmo- 

 spheric and other pressures changes into sticky frothing. 

 Exact temperature data cannot therefore here be expected. 

 The following Table is an example of the earlier results 

 obtained, P being the pressure in centimetres of mercury, 

 and T the corresponding boiling-point in degrees Centigrade. 



Table I.— 



Boiling 



-points of Sulphur. 



p. 



T. 



P. 



T. 



°C. 



P. 



T. 



centim. 



°C. 



ceatim. 



centim. 



°C. 







218 



4-8 



2$8 



21-2 



374 







205 



7-0 



316 



39-S 



410 



24 



263 



112 



337 



76-0 



448 



The next Table contains results of a later date, in which 

 much care w<as taken to guard against the difficulties men- 

 tioned. D 20 , the twist in degrees of arc, has been added to 

 show the sensitiveness of the torsion-galvanometer. 



* Ramsay and Young, Journ. Chem. Soc. xlix. p. 37, 1887; Landolt 

 and Boernstein's Tables, p. 58 (Berlin, Julius Springer, 1883). T may 

 ad\ert in passing to the discussion between Ramsay and Young and 

 Kahlbaum. The former, corroborating Regnault's law, maintain that 

 vapour-tensions, whether obtained by the static or the dynamic mode of 

 measurement, are identical. Kahlbaum claims to have found a differ- 

 ence, and he is sustained by 0. Schumann (Chem. Ber. xviii. p. 2085, 

 1885). Both authors make use of Landolt's vapour-tensions. 



