The Relation between Weight and Volume 67 



or 50 g. of water. In using these, the weighing of the 

 distilled water may be dispensed with, provided that 

 the flasks are carefully made. These vessels are called 

 " density flasks " or " pyknometers " (Gr. pyknos, 

 dense) and two common forms are shown in Fig. 24. 



Q 



Fig. 24. 



Of these A represents the better form but its use 

 demands more careful manipulation. If such a flask 

 is available, the student should perform 



EXPERIMENT 21. Weigh the flask empty, after first 

 making sure that it is quite clean and dry, both within 

 and without. . Completely fill it with the liquid to be 

 dealt with. Holding the flask with a clean duster, 

 push the perforated stopper home. Remove the excess 

 of liquid from the outside of the flask with the duster, 

 care being taken to leave the hole in the stopper quite 

 full of liquid and to avoid touching the flask directly 

 with the warm hand. Weigh the flask and its contents. 

 Subtracting the weight of the empty flask from the 

 weight of flask and liquid gives the weight of liquid 



52 



