Appendix V D. Determination of Boiling Point

(Ph. Eur. method 2.2.12)

The boiling point is the corrected temperature at which the vapour pressure of a liquid is equal to 101.3 kPa.

Apparatus The apparatus is that used for distillation range (2.2.11) with the exception that the thermometer is inserted in the neck of the flask so that the lower end of the bulb is level with the lower end of the neck of the distillation flask and that the flask is placed on a plate of isolating material pierced by a hole 35 mm in diameter.

Method Place in the flask (A) 20 mL of the liquid to be examined and a few pieces of porous material. Heat the flask so that boiling is rapidly achieved and record the temperature at which liquid runs from the side-arm into the condenser.

Correct the observed temperature for barometric pressure by means of the formula:

t1
 = 
the corrected temperature,
t2
 = 
the observed temperature at barometric pressure b,
k
 = 
the correction factor as shown in Table 2.2.11.-1 under Distillation Range,
b
 = 
the barometric pressure, in kilopascals, at the time of the determination.