Viscosities of C cesium Salts. 15 



2. The fragility of the older form makes rapid handling practically 

 impossible. 



3. The instrument is difficult to dry and polish before weighing. 

 To remove these defects the form shown in fig. 4 was devised, and 



has been found to be more convenient and accurate than the old form. 

 In the figure the symbols have the following significance : 

 (a) A reservoir of thin-walled glass tubing which may be of any 



desired capacity, those in use in this laboratory holding, respectively, 



about 6, 10, and 20 c.c. 



(&) Tapering tube of thin glass reaching almost to the bottom of (a), 



and having a bore at the open end equal to or slightly greater than that 



of the capillary (0.5 to 0.75 mm.). This tube is of use in drying and 



filling the instrument. 



(c) Outlet tube sealed on to the end of 6. This is drawn out slightly 

 at the end and is bent at an angle of 60 close to the reservoir. 



(d) Slight enlargement in c which holds in position the wire used 

 to suspend the pyknometer on the balance. 



(e) Expansion bulb of sufficient size to accommodate the increased 

 volume of any liquid when warmed 10. If the instruments are used 

 only at 25 this bulb need be only very small. 



(/) Fine line etched around the capillary at the lower limit of the 

 taper in the bulb e. 



In adjusting the instrument when filled, a rubber tube is attached 

 to the horizontal capillary above e, and the liquid blown out gently 

 until the level in e just reaches the mark /. The excess of liquid 

 is then removed from the end of c with filter paper. On removing 

 the pressure, the level of the liquid in c falls until it comes to rest 

 near the bend in the capillary, thereby lessening the danger from evap- 

 oration or accidental spilling after adjustment. 



The advantages of this form of pyknometer can readily be seen, e. g., 

 the projecting arms are both short and hence not easily broken. Also, 

 the net weight has been materially lessened, since the amount of neces- 

 sary capillary has been reduced to a minimum. The instrument is 

 also much easier to clean and dry before weighing than the older form. 



This pyknometer may be provided with ground-on caps when used 

 with alcohol or other volatile liquids, to prevent possible evaporation. 



