Relations oj Liquids and their Saturated Vapours. 93 



tziL = Po[7 _ i( , ] + g] 

 v x —v 



= the same at t ^l° ; hence we obtain 7 = 186°*4, and P = 3-485 



(* =14°-51, / 1 = 26°-41, t> = 1-02326, Vl = 1-04386). 



The previous values by M. Drion's observations were 7 = 187° 

 and P =3-545. 



The next line (D C) on chart Q was drawn through the a points 

 of M. Pierre's hydrobromic ether by means of a thin flexible 

 steel straight edge. To judge the value of such a set of points, 

 a light pencil-line is drawn in the general trend, and then the 

 middle points are examined to see if there are any parallel to 

 this line ; if so, the straight edge (set on its edge) is brought to 

 them and bent up a little on each side so as to pass over or 

 through the extreme points if possible. The result, it will be 

 observed, is favourable; the points C and D are selected for 

 computation, from which is obtained 7=253° and P =2*97; 

 the greatest discrepancy is at 28°, where the divergence is o, 18. 



In this way the points for hydriodic ether were also treated, 

 and E, F selected, from which 7 = 312° and P =2'75. The 

 greatest divergence is at 58°, where it amounts to about 0, 2. 



A similar projection was made with the short series of obser- 

 vations on sulphuric ether* : the points ranged well ; the two 

 selected were 23°-36, -03657; 38°-14, -06216, which givey =211°, 

 P = 3*21. Others give 7 various up to 250°. 



§ 33. The series on chloroform f was graphically examined, 

 and the three highest were found very exactly in a line, giving 

 7 = 334°, P = 2-52; but the lower observations gave points 

 which were quite out of range, and showed that the law of con- 

 tinuity was not maintained ; the divergence amounts to nearly 1°. 



The series on chloride of silicium and chloride of phosphorus 

 are also wanting in regularity. 



§ 34. The series on the bichloride of carbon are good ; they 

 give 7 = 318°, P = 2'73. The bromide of hydrocarbon is No. 5 

 of Plate IV. On extending the general line it cuts the axis at 

 7 = 440°. If the two lower points are preferred, the line passes 

 through the upper point and cuts the axis at 423°. 



Turpentine is No. 7 of Plate IV. ; the line cuts the axis 

 at 461°. 



The vapour-lines of all these liquids have been fixed by Reg- 

 naulf s observations, which are projected on Plate I., and they 

 all trend to one point at the absolute zero of temperature, called 

 the ether nodal point, shown in Plate III. 



* Ann. de Chim. et de Phys. vol. xv. p. 361. 

 t Ibid. vol. xxiii. p. 208. 



