STUDIES ON AGAR-AGAR IN JAPAN 219 



decrease of entropy by deformation. The agar molecule is considered 

 to be a galactan chain accompanied by sulphate radicals here and there. 

 A lattice-like configuration of these poly-electrolyte chains in water 

 might be the internal structure of the gel state. 



c) Viscosity of much diluted agar-hydrosol (18) :— The gel-forming 

 property of agar is so strong that even a 0.04% solution distinctly ex- 

 hibits elasticity as has been described in (a), and anomalous viscosity 

 is observed in these concentrations. Accordingly it is necessary to ex- 

 periment with much diluted (under 0.04%) systems in order to test the 

 purely viscous behaviour of the solution. 



Measurements were made by the ordinary methods using Ostwald's 

 visco-meter in the concentration range 0.01-0.04%, and |sp./c (specific 

 viscosity divided by concentration) were plotted against concentration. 



|sp./c decreases with the decrease of concentration, passes through 

 the minimum, and then increases again with further decreases of con- 

 centration, and if a strong electrolyte such as KCl is added to the solu- 

 tion, ^sp./c decreases eventually with the decrease of concentration. 

 This behaviour is the same as that of other poly-electrolyte solutions. 



Intrinsic viscosity defined as [|] = [|sp./c]c ^ o is concerned with 

 the extension of the molecule in the solution. And from the evaluation 

 of the intrinsic viscosity of agar-hydrosol, it is supposed that this poly- 

 electrolyte has a much stretched non-spherical configuration in water; 

 [^] of agar-hydrosol is much larger than that of the ordinary random- 

 coil non-polar polymers. 



IV. Organic-chemical Investigations on Agar-agar 



Araki has investigated the chemical constitution of agar-agar. He 

 isolated D, L-galactose and L-galactose (19) and reported on acetylated 

 agar, heterogeneous composition, and percentage compositions (20) of 

 agar-agar. L-galactose from methylated agar has been confirmed (21). 

 2,4,6-trymethyl-D-galactose, 2,4-dimethyl-3, 6-anhydromethyl-L-galacto- 

 side, 2-methyl-3, 6-anhydro-L-galactose dimethylacetal and pentamethyl- 

 D-galactosido-3, 6-anhydro-methyl-L-galactoside have been isolated from 

 methylated agar (22). 3,6-anhydro-galactose has been synthesized (23) 

 and 3,6-anhydro-L-galactose has also been isolated from agar-agar (24) 

 as its dimethylacetal by methanolysis of agar-agar and as its diethylmer- 

 captal by mercaptolysis, from which 3,6-anhydro-L-galactose has been 

 separated in free state. Again isolation and chemical constitution of 

 agarobiose and isoagarobiose have been studied (25). A new disaccha- 

 ride C12H20O10 has been obtained by hydrolysing agar-agar with IN 



