14 



Conductivities and Viscosities in Pure and in Mixed Solvents. 



tube drawn out to a small diameter is then inserted through d and / 

 into b, and toluene allowed to run in until the reservoir is filled and 

 also the space in a above the mercury. The tube d is then sealed, 

 and by adding or withdrawing mercury from the capillary the contact 

 level may be adjusted for any desired temperature. 



By this method a toluene-mercury regulator is constructed with a 

 range of 50 or more, all adjustments being made through the capillary, 

 which should be of from 1.5 to 2 mm. bore, according to the capacity 

 of the toluene reservoir. 



All danger of the toluene creeping into the capillary is removed, since 

 the tubes e and/ terminate in the same liquid which is contained in them. 



This trap is compact, not easily broken, and is comparatively simple 

 to construct. In addition to this, it lies within the plane of the reser- 

 voir and contact tubes. 



FIG. :j. FIG. 4. 



A NEW FORM OF PYKNOMETER FOR LIQUIDS. 1 



The investigators, P. B. Davis and L. S. Pratt, have recently had occa- 

 sion to carry out a large number of density determinations w r ith various 

 liquids. For this purpose a modified form of the Sprengel pyknometer, 

 as described by Jones and Bingham 2 and Jones and Veazey, 3 was first 

 adopted, but was found to have the following disadvantages: 



1. In instruments of large capacity (10 to 20 c.c.) the long capillary 

 side-arm adds greatly to the weight and hence impairs the accuracy of 

 the pyknometer. 



'Devised with L.S.Pratt, 2 Amer.Chem..Tourn.,34, 48(1905). "Zeit-phys-Chem.^!, 641 (1908). 



