270 



BOTANICAL GAZETTE 



[OCTOBER 



It has long been known that carbohydrates form salts with 

 metals, and that they react with the chlorides, sulphates, and 

 other salts of the heavy metals, such as copper, lead, mercury, gold, 

 iron, silver, etc., to form the corresponding carbohydrate salt with 



TABLE III 



Swelling of dried gelatine plates 0.5 mm. in thickness 

 at i6-i7°C; swelling in water 600 per cent 



Normal concentration 



Water 



Propionic acid 



Alanin 



O 1 



IOO 

 IOO 





91 



83 



88 



O ,0^ 



256 



185 

 130 



83 



O.OI 



IOO 



0.002 



IOO 

 IOO 



86 



. 004 



75 



• 





McGee 



has determined the hydrogen ion concentration of a number of 

 heavy metal salts in 2 per cent aqueous solution, and also in mix- 



■ 



tures of 2 per cent of the salts plus 2 per cent d-glucose. A 2 per 

 cent solution of d-glucose in water showed Ph = 6.6. 



TABLE IV 



Hydrogen ion concentration expressed as Ph of 2 per cent solutions of 

 some heavy metal salts and of same mixed with 2 per cent d-glucose 



ZnCU 



6.3 



AgN0 3 



5-5 



HgCl, 



3-9 



CuSO, 



4-6 



ZnCl 2 



+ 

 glucose . . . 



54 



AgNO, 



+ 

 glucose . . . 



5-3 



HgCl, 



+ 

 glucose . . . 



3-8 



CuS0 4 



+ 



glucose . . . 



44 



It is apparent that in the addition of the glucose to the heavy 

 metal salts the acidity of the mixture is appreciably raised. 



The amino acids being amphoteric electrolytes, it is to be 

 expected that they would behave like acids toward bases, and 

 like bases toward acids. Furthermore, there are a number of 

 reactions of which the amino acids are capable which may be of 

 importance in interpreting their behavior toward agar. Thus 

 the simplest amino acid, glycocoll (NH 2 CH 2 COOH), can appar- 

 ently give rise to an internal salt, NH 3 CH 2 COO. Glycocoll in 

 solution would then exist in equilibrium as the un-ionized 



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