244 



Mr. F. D. Brown on the Physical [May 31, 



The following Table gives the volume o£ Fraction III. at every ten 

 degrees from 0° to 100° ; these numbers are measured direct from the 

 curve, and represent the experiments quite as well as if calculated by 

 means of an equation of the formula 



V=l + a * + /3* 2 + y* 3 . 



Tempera- 

 ture. 



Volume as 

 measured from 

 curves. 



Yolume 

 given by 

 Pierre. 



Tempera- 

 ture. 



Volume as ' 

 measured from 

 curves. 



Volume 

 given by 

 Pierre. 



O 







1-00000 



1-000 



o 



60 



1-06852 



1-069 



10 



1-01052 



1-010 



70 



1-08128 



1-082 



20 



1-02142 



1-021 



80 



1-09446 



1-096 



30 



1-03274 



1-0324 



90 



1-10802 



1-1105 



40 



1-04436 



1-044 



100 



1-12200 



1-125 



50 



1-05600 



1-056 



104-5 





1-132 



The difference between the numbers at the higher temperatures is 

 doubtless partly due to the fact that Pierre measured the density at only 

 four temperatures, viz. 0°, 9°*1, 52°-6, and 75°-3, and then calculated 

 the above series of numbers by means of a formula of interpolation ; it 

 will be observed that a small error in the determination of the density at 

 75°*3 would be sufficient to cause the discrepancy referred to. 



The vapour-tension of the normal iodide was determined by boiling in 

 the apparatus described above ; here, again, Fractions I. and III. only 

 were employed. The following Table gives the results obtained : the 

 observations marked thus * were made with platinum foil in the boiling 

 liquid ; with the others this was not the case. 



Fraction I. 



Fraction II. 



No. of 



Boiling- 



Pressure in 



No. of 



Boiling- 



Pressure in 



Obs. 



point. 



millims. 



Obs. 



point. 



millims. 



3 



52-66 



138-9 



2 



53-06 



138-6 



2 



59-86 



184-7 



1 



53-17 



139-8* 



1 



62-95 



208-0 



1 



53-26 



139-6 



1 



72-12 



289-9 



1 



56-17 



157-9* 



1 



83-32 



424-9 



3 



61-80 



195-9 



1 



93-85 



591-9 



1 



62-70 



203-0* 



1 



101-14 



735-0 



1 



70-45 



269-6 



1 



102-00 



753-4 



1 



79-11 



365-3 









1 



84-15 



431-3* 









1 



90-05 



520-0 









1 



96-81 



640-4 









1 



100-21 



707-1 









1 



100-45 



712-7* 









1 



101-37 



732-1 



