THE DENSITY OF LIQUIDS 433 



air. The filling apparatus consists of a glass bulb to which 

 are connected three tubes : one of these passes from the 

 bottom down through a rubber stopper to the pyknometer ; 

 the other two project from the top of the bulb, one vertically, 

 to which is attached a two-way tap so that connection can be 

 made to the pump or to a tube for admitting dry air, the other 

 projecting horizontally and then bending downwards to the 

 round-bottomed flask containing the liquid. Filling is carried 

 out by first exhausting and then tilting the apparatus so that 

 the liquid runs towards the pyknometer ; on admitting dry 

 air some liquid is forced into the pyknometer and by repeating 

 the process it can be completely filled. A small air-bubble is 

 introduced with the aid of a drawn-out tube, the pyknometer 

 is emptied, and is then attached in an inverted position, to 

 the filling apparatus. By repeating the exhaustion and filling 

 with dry air, the liquid can be returned to the flask without 

 coming into contact with moist air. The repeated admission 

 of dry air and its subsequent exhaustion is a rapid and efficient 

 method of drying the apparatus. The adjustment in the 

 thermostat is made by removing with filter paper the excess 

 of liquid in the cup, and then the liquid in the capillary down 

 to the mark by means of a rolled-up piece of filter paper, or a 

 finely drawn-out tube in which the liquid rises by capillarity. 

 A lens can be used to view the position of the meniscus. Air 

 is blown into the cup to remove vapour and the stopper is 

 put in place. 



A combined specific gravity bottle and dilatometer has 

 been described by Browne (6) for determining the small 

 changes of volume which occur when sugar solutions undergo 

 inversion or when sugar solutions are mixed. The apparatus 

 consists of a narrow tubular body holding 30 ccs. connected 

 at the bottom with a capped graduated capillary tube and 

 contracting at the top to a small opening. The latter is 

 slightly funnel-shaped and is ground on its inner surface so as 

 to receive a thermometer which is also ground so as to fit tightly 

 on insertion. The displacement of the thermometer is about 

 7 ccs., and this leaves a capacity of 23 ccs. for the instrument 

 when stoppered. 



The scale upon which the changes of volume are measured 

 is graduated so that one division equals 0*001 cc. and by means 

 of a magnifying-glass reading can be made to 0*0001 cc. The 



