440 



BANANA GEL 



used when necessary to produce the required pH values. That 

 sodium chloride did not play a positive part in the gel formations was 

 evident from the fact that the banana extracts in many experiments 

 were prepared with sodium chloride solution. 



When gel formation occurred, the volume increases were 100 per 

 cent or less, when no gel formation occurred the volume increases 

 ranged from 100 to 400 per cent in 48 hours. In a number of experi- 

 ments, the pH of the outside liquid changed from 7.0 to 6.0 or even 

 less. Whenever this occurred, no gel was formed inside the bags. 



These results showed that for the formation of a gel from banana 

 extract by dialysis against tap water, the presence of a calcium salt 



Solutions. 



CaCOa 0.00020 to 0.00024 m^ 



CaCOs . 00020 to . 00024 m; phosphate buffer*, 



35 cc. : 2 liters 



CaCOs Saturated, excess solid 



CaCOs 0.00024 m 



Phosphate buffer,* 35 cc. : 2 liters , 



MgS04 0.00024 M 



MgS04 0.00024 M 



Ca(0H)2 Saturated, excess solid CaO 



and an alkalinity corresponding to pH 7.0 or more were the important 

 factors. 



In order to determine whether the collodion bag as such played a 

 part in the gel formation or whether possibly interfering substances 

 were removed by dialysis, the following experiments, in which a 

 number of different salts were added directly to banana extract at 

 different hydrogen ion concentrations, were carried out. 



///. Actions of Salts on Banana Extract at Definite Hydrogen Ion 



Concentrations. 



No satisfactory quantitative methods for the comparison of gels, 

 the readiness of their formation, and their chemical compositions, 



^ 20 to 24 parts per million. 



* Clark, W. M., The determination of hydrogen ions, Baltimore, 1920, 76. 



