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4.6 DETERMINATION OF BOILING TEMPERATURE​

      The boiling temperature is the corrected temperature at which the vapour pressure of a liquid is equal to 101.3 kPa (760 Torr). 

Apparatus

      The apparatus is that used for the “Determination of Boiling Range” (Appendix 4.5) with the exception that the thermometer is inserted in the neck of the flask so that the lower end of the mercury reservoir 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 = t₂ + k (101.3 – b),

where t₁ = the corrected temperature,

t₂ = the observed temperature,

 k = the correction factor taken from Table 1 under the “Determination of Boiling Range” (Appendix 4.5), and

 b = the barometric pressure, expressed in kilopascals, at the time of the determination.