378 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



paper. DeMetz,27 ji^ quoting Amagat, however, gives 0.05.379 as Ama- 

 gat's value at 0°. The source from which this knowledge was obtained 

 is not clear. Amagat's results, obtained with seven different piezom- 

 eters, vary among themselves by 2 per cent. De Metz gives O.O5374 

 at 0° and a pressure range not over 50 kgm., as the mean of results 



.00020 



.00015 



.00010 



-^00005 





 '00005 

 .00010 

 00015 

 DOOlO 

 O00Z5 

 .00030 



3 4-56 



fci 



I 2 3 4- 5 6 7 6 9 10 11 12 



PRESSURE, KGM/CM'XIO:' 



Figure 8. The deviation curve for the change of volume at 22°. Tliis 13 

 to be used with the formula on page 376. 



with four piezometers differing among themselves by 5 per cent. De 

 Metz also gives the temperature coefficient of compressibility. This is 

 higher than the value found above, but is such as to bring de Metz's 

 value at 22° up to 0.06394, almost identical with the present deter- 

 mination at that temperature. Lately Richards ^8 has determined the 

 compressibility to 500 kgm. He gives O.O537I for the pressure range 

 0-500, at a temperature not specified, probably room temperature. 

 Previous work by Richards, however, had given a value for the tem- 

 perature coefficient of the mercury the same as that of the glass piezom- 

 eter. This temperature coefficient is very much smaller than found 

 above, producing a change from O.O537IO at 0° to 0.053724 at 20°. 



27 Do Aletz, loc. cit. 



"* Richards, loc. cit. 



