BY JAMES M. PKTRIE. 855 



(b) Gallois' test gave positive results witli both substances. 

 When the crystals are treated with mercuric nitrate, a yellow 

 precipitate first forms, which, on evaporating to dryness, gives a 

 deep red colour; on cooling, this colour slowly disappears, to 

 return on being reheated. (Fres'. Zeitschrift fur anal. Cheniie, 

 iv., 1865, 264). 



These two charactei'istic reactions are due to the oxidation of 

 inositol to a (luinonoid substance known as rhodizonic acid, whose 

 salts with calcium, barium, and mercury, possess the bright 

 colours described. 



The reduced substance is thus proved to be one of the inositols, 

 and the original compound isolated from the plant-extract is its 

 methyl ester. 



(10) Optical propfrfifis. — A polarimetric determination of the 

 two substances was made with a Schmidt and Haensch polari- 

 meter reading to one-hundredth of a degree. 



Methyl inositol 0"5gm. was dissolved in 10 c.c. of distilled 

 water at 16°C., and a Ijevo rotation w^as recorded of - 4*01 in a 

 1 dcm. tube. 



The specific rotatory power [o]^- = - 80-2; [MJ^J- = - 155-0. 



The solution was boiled for two minutes, and after cooling to 

 16°C., was again read in the polarimeter. No change was ob- 

 served, such as is due to mutarotation among the hexoses. 



Inositol, the de-methylated compound, 0"0741gm. was dissolved 

 in 10 c.c. of water at 16°C., and showed a Ifevo rotation of 

 - 0'48° in a 1 dcm. tube. 



Specific rotatory power [a]^' = - 64-8; [MJ^J' = - 116'7. 



(11) Hydration. — The Isevo-inositol was obtained by crystallisa- 

 tion from cold aqueous alcohol, and contained no water of crys- 

 tallisation. When crystallised from water, it was also obtained 

 in anhydrous crystals. 



Now Maquenne and Tanret have described some important 

 differences with regard to the water of crystallisation in the 

 isomeric inositols."^ They found that — 



* Reeherches sur I'inosite, Maquenne — Annales de ehemie et de physique, 

 xii., 1887, 94; Comptes lendus, ex., 1890, 87. 



