1920] 



M AC DOUG A L & SPOEHR—AGAR 



271 



NH 2 CH 2 COOH together with its ions and with NH 3 CH 2 COO, as 

 well as a hydrated form OHNH 3 CH 2 COOH. The existence of 

 this latter compound has been used to explain why acids such as 

 glycocoll do not follow the simple Ostwald dilution law. The 

 recent observations of Birckner 3 on the interaction of ethyl 

 alcohol and certain amino acids may be interpreted in favor of the 

 theory of salt formation of the alcohol with the amino group. 

 Further insight as to whether the increased swelling of agar in 

 amino acids is due to simple salt formation or to the formation of a 

 compound related to the form OHNH 3 CH 2 COOH was sought 

 in a study of the behavior of agar toward ammonium hydroxide 

 and some related substances. 



auxo 



Swelling of agar in alkaline hydroxides and in ammonium salts 



A study of the behavior of agar in solutions of various alkaline 

 hydroxides revealed a number of facts worthy of notice. The 

 first experiments were conducted in the usual manner with 25 cc. 

 of the hydroxide solutions in the dishes containing the pieces of 

 agar. An examination of the 

 thus obtained showed a remarkable similarity, in that after about 

 24 hours there was a marked acceleration in the rate of swelling, 

 and the final results were very similar in all cases. In figs. 1 and 

 2 the curves of swelling are reproduced for potassium hydroxide 

 and ammonium hydroxide. The total swellings thus obtained in 

 the various solutions are given in table V. 



TABLE V 



ALKALINE 



HYDROXIDE SOLUTIONS AT IjfC.J TOTAL SWELLING OF 

 AGAR PLATES IN WATER 3950 PER CENT 



Normal concentrations 



O.OI . 

 O.OOI 



Water 



XH4OH 



LiOH 



NaOH 



IOO 

 100 



63 



77 



60 



77 



55 

 75 



KOH 



49 



81 



Titrations after 24 hours of the solutions in which the agar 

 had been swelling showed that the solutions had decreased 



3 Birckner, V., Jour. Biochem. 38:245-254. 1919. 



