Evaporation in Burettes 161 



For any given series of readings the burettes were filled and the 

 solutions allowed to attain the temperature of the room. In order to 

 have the surfaces of the solutions in the several burettes all the same 

 distance from the top at the beginning, a siphon extending down 10 cm. 

 from the rim was used to remove any solution or liquid above this point. 

 After a few minutes the first reading was made. The others were taken 

 on the morning's of succeeding days, before the small laboratory was 

 opened and the temperature had an opportunity to change much. The 

 sets were only partially protected from currents of air. 



This method of procedure does not furnish data on the actual rate 

 of evaporation for any definite conditions, as no attempt was made to 

 hold any of the variable factors constant during the determinations ; 

 but it does furnish one with an approximate idea of the error involved 

 as a result of evaporation of standard solutions under the usual con- 

 ditions prevailing in the laboratory. 



The following tables include the data obtained for solutions of 

 sodium chloride of various concentrations, water, benzene and toluene. 

 The total loss in milliliters is given for the various intervals of time. 



