388 ENZYMES 



is filtered off and the filtrate evaporated on a water bath to the 

 consistency of a syrup. On the addition of alcohol, containing 

 one-tenth of its volume of ether, inosite is deposited in prismatic 

 crystals. 



Inosite has a sweet taste, is soluble in water but insoluble 

 in alcohol and ether. It crystallizes in prisms, and does not 

 give any reactions characteristic of true hexoses. For instance, 

 it is not fermentable, it does not reduce Fehling's solution, and 

 its solution does not give a brown coloration with potash. 



Identification. 



1. When moistened with a little dilute nitric acid, then 

 evaporated almost to dryness, and made alkaline with am- 

 monia, the addition of a few drops of chloride of calcium 

 produces a rose-red coloration. 



2. A solution of inosite evaporated to dryness with a few 

 drops of mercuric nitrate produces a yellow stain which on 

 heating turns red. 



3. Solutions of inosite are not optically active. 



With regard to its significance in the plant there is evidence 

 to show that inosite is a transitory substance and is used up in 

 the synthesis of other substances. 



According to Posternack * a large amount, 80-90 per cent, 

 of the phosphorus of certain seeds exists in the form of phytin ; 

 it occurs, for instance, in the globoid portion of aleurone grains, 

 and the seeds which contain it also possess an appropriate 

 enzyme phytase for its decomposition into phosphoric acid 

 and inosite.f 



With regard to the formation of phytin little is known ; 

 Posternack considers that it is formed by the combination of 

 formaldehyde, produced in the early stages of photosynthesis 

 with phosphoric acid. 



The tenability of this opinion is obviously bound up with 

 the formation of formaldehyde in green leaves (q.v.). 



Phytin appears to be an acid calcium and magnesium salt 



* Posternack : " Compt. rend.," 1903, 137, 202, 337, 439. 

 t Cf. Suzuki, Yoshimura and Takaishi : " Bull. Coll. Agric, Tokyo," 1907, 

 7, 503. See also Rose : " Biochem. Bull.," 1912, i, 428. 



