MEASUREMENT OF OSMOTIC PRESSURE $?$ 



column have been calculated on the assumption that the sugar 

 in the solution is present as C^E^On, 6ITO. 1 A remarkable 

 result is seen on studying the list of errors tabulated in 

 column 8 ; although the calculated and observed figures are 

 even now not in agreement, the error is quite steady through- 

 out at o'ig, o'2i, o*2i, o"20, C20, o'22 atmosphere; such a result 

 indicates that a formula has at last been arrived at which 

 expresses the properties of the solutions perfectly, with the 

 exception that some factor, the nature of which is still un- 

 disclosed, increases the observed values by one-fifth of an 

 atmosphere above those which have been calculated for the 

 hydrate CuHsbOii, 6H 2 0. 



In the above pages, the opinion has been asserted that 

 direct measurements of osmotic pressure are of such vital 

 importance that the enormous labour that has been expended 

 upon them has been both legitimate and fruitful. If the de- 

 tailed story of these arduous experiments serves to bring 

 home to readers some idea of the motives that inspired the 

 workers and of the difficulties that they had to overcome, the 

 purpose of the writer will have been fully carried out. 



1 The figures given by Findlay are for 5H 2 ; his corrections have been 

 increased in the ratio 6 : 5 to give the figures tabulated in column 7 of the table. 



