IQ20] 



MacDOUGAL & SPOEHR—AGAR 



2 73 



considerably in strength in this time, probably due to absorption of 

 C0 2 from the air, and, in the case of the ammonium hydroxide, to 

 volatilization. Experiments were then made in which the solutions 

 were removed from the agar and replaced by fresh solutions every 

 12 or 24 hours. The results thus obtained differ radically from the 

 previous ones, as to form of the record made by the swelling agar, 

 as well as to the total amount of swelling attained in each case. 

 Figs. 3 and 4 give the auxograph record of the swelling agar in solu- 

 tions renewed every 1 2 hours. The relatively sudden increase in rate 

 of swelling after 24 hours, which was so striking in the experiments 

 in which the solutions were not renewed, is entirely absent. This 

 accelerated swelling undoubtedly represents the rate of swelling in a 

 solution which is but slightly alkaline and approaches that obtained 

 in water. Furthermore, the total swelling of agar in KOH, NaOH. 

 and LiOH is decidedly lower in the solutions which had been 

 renewed. Especially noteworthy, however, is the fact that ammo- 

 nium hydroxide in 0.001 normal concentration produces a swelling 

 considerably in excess of water when the solution is renewed. This 

 observation has been verified repeatedly. 



NIL OH 



LiOH 



considerable, particularly in the more dilute solutions. 



TABLE VI 

 Swelling of dried agar plates at i5°C. in alkaline hydroxide solutions, 



RENEWED EVERY 12 HOURS; TOTAL SWELLING OF DRIED AGAR 



PLATE IN WATER 3950 PER CENT 







Normal concentration 



Water 



NH4OH 



Ethyl 

 amine 



LiOH 



NaOH 



KOH 



O.OI 



IOO 2< 



31 



88 



24 



40 



21 



35 



21 



O.OOI 



IOO 



"5 



29 





^^^^ ^^^ ^^^^ 



w 



Owing to the fact that in solutions of ammonium hydroxide 

 and ethyl amine there exist equilibria respectively between dis- 

 solved NH 3 and the hydroxide, and between dissolved C*H 5 XHa 

 and its hydroxide, the condition in solutions of these substances, 

 particularly in the more concentrated solutions, offers a rather 

 complicated situation not dissimilar from that obtaining in solutions 



