52 SOME EECENT RESEARCHES IN PLANT PHYSIOLOGY 



The determination of the percentage of water in a tissue 

 may accordingly be carried out by placing it in a weighed 

 flask, and distilling with alcohol and benzene. In such 

 cases' it is advisable to protect the end of the stillhead 

 from being splashed by the alcohol containing extracted 

 matter. When the flask has been distilled as nearly to 

 dryness as possible, it is disconnected and the remainder of 

 the liquid distilled away without a condenser, the entrance 

 of moisture being prevented by a drying tube attached to 

 the cork. The difference between the original and final 

 weights is the weight of water and other volatile sub- 

 stances, if any, lost during the treatment. 



This method appears to offer possibilities for determining 

 water of crystallization in many cases, and may be of use in 

 deciding whether it is present as " water of crystalliza- 

 tion " or as " water of constitution." 



NOTE. It has been found that since errors are largely 

 magnified in the equations for three unknown quantities 

 given on p. 49, the best results appear to be obtained by 

 choosing the conditions so that glucose is almost entirely 

 removed as well as maltose. The residual reducing-power 

 of the glucose compensates for the slight loss of fructose 

 when the two are present in anything roughly approaching 

 equal amounts. A small correction can be introduced for 

 the residual glucose. 



