THURAS: DENSITY MEASUREMENTS 



611 



The only constant error is that due to a permanent change 

 in the volume of the bobbin. To reduce this error the bobbins 

 were constructed with great care. They are made of normal 

 Jena glass No. 16 111 and were carefully annealed about eight 

 months ago. There has not been sufficient time to determine 

 their change in volume due to aging, but it is believed that they 

 have now attained a volume that is constant enough not to affect 

 appreciably the measurements of density. T. W. Richards has 



J2Q. 



J1QCL. 



CALIBRATION CURVES 



m 



18 



20 



Equilibrium temperature in degrees ceirtifrode 

 22 24 2C 28 30 32 34 Si 38 40 



42 



Fig. 2. Relation between equilibrium temperature and density and salinity. 



examined carefully the effect of aging, using various kinds of 

 glass, and finds that after three or four months the change in 

 volume of the glass is exceedingly small. 



To determine the error due to sudden heating and cooling, 

 the bobbin and liquid were placed in a sealed glass tube and the 

 following results were obtained, using a Beckman thermometer to 

 measure temperatures: 



Equil. temp. 



From room temperature 20 . 74 



After being in a bath of 56°C. for 10 minutes 20.75 



After being in an ice bath for 10 minutes 20.755 



After being in a bath of 80° for 20 minutes 20.75 



