88 PROCEEDINGS OF THE CANADIAN INSTITUTE. 



As it is desirable that the boiling points of the mixtures should be varied at 

 pleasure, a subsidiary piece of apparatus has been constructed by means of which 

 the pressure in the boiling vessel may be maintained constant at any desired point 

 from 20 — 1200 mm. This pressure-regulator consists of two five-gallon jars, of which 

 the first is attached directly; to an air pump, and the second to a U-tube manometer 

 and to the boiling apparatus (between condenser and fifth opening) ; communication 

 between the jars is afforded through a tap, which is usually closed, but may be 

 opened by an electrical device set in motion whenever the mercury of the mano- 

 meter (in the open limb) rises high enough to form contact with an adjustable 

 platinum wire. 



