136 



THE CARBOHYDRATES. 



[CH. V. 



The heating apparatus. -Use the apparatus shewn in fig. 15. 

 In a 200 cc. Erlenmeyer flask of Resistance glass, and of about 6 cm. 

 basal diameter, place 60 cc. of distilled water. The flask is fitted 

 with a 2-hole rubber stopper carrying a thermometer so graduated 

 that the stem above 34 C. is visible above the upper edge of the 

 stopper. The lower end of the thermometer should be about 2 mm. 

 from the bottom of the flask. 



Fig. 15. Cole's apparatus for maintaining a standard heating power. 

 The manometer tube contains a dilute solution of eosin or other dye. It 

 also contains a globule of mercury which nearly fills the bottom of the tube. 

 This prevents the rapid oscillations of pressure due apparently to the explo- 

 sions of local gas engines. 



Turn on the tap B to its full extent and light the flame of 

 a Bunsen or Meker burner, which is placed under a piece of asbestos 

 gauze carried by an adjustable ring stand. The gauze should be 

 from 4 to 6 cm. above the top of the burner. Tighten the screw A 

 till the pressure is reduced about one-third. Allow the gauze to get 

 thoroughly heated and then place the flask in the centre of the 



