<>\ THE DIFFUSION OF LIQUIDS. 11 



pnr j 



2 " (8) 



Hence it' S p be the corresponding area for the curve at t=o, we 

 have 



S B 



Sp by 



and therefore 



H-lt), 



.so that if it is only required to find h, it is sufficient to determine S ;) 

 and s„ in anv arbitrary unit. 



I used only Sj and Sj in my reductions for the reason already 

 given. The values of log ]0 (—^— J were tabulated against t, and the 



ratio'logjo ( — — ) /t was determined by the method of the least squares, 



and finally k was calculated by the equation 



ft = 2. SO 26^-log 10 (-AA ( , Q) 



§ 4. In my experiment, the diffusion vessel is made of brass 

 (though evidently glass is preferable). Its height is 48 mm., its 

 thickness 10 mm. and its breadth 56 mm. The spectrometer circle 

 reads to 10 "by verniers, and the readings of two distinct settings for 

 the diffusion curve seldom differed by more than 20". The angles 

 of the prism used are 



A = 45° 2' 25" 

 B= 44" 55' 35" 

 C- 90° 1' SO" 



The index of refraction N was measured by filling the vessel with 

 liquids of known indices, or when vacant, and the mean of several 

 experiments gave 



N =1.63175. 



