V] HYDROLYZING ENZYMES 51 



Laevulose reduces Fehling's and other copper solutions. It yields 

 the same osazone as glucose with phenylhydrazine hydrochloride and 

 sodium acetate. It also forms an osazone with methylphenylhydrazine 

 (m.p. 158° C), a reaction which constitutes a distinction from glucose 

 since the latter gives no osazone with this substance, 



Expt. 44. Tesits for laevulose. The following tests should be performed with a 

 0-2 "/o solution of laevulose in the same way as for glucose (see p. 48). 



(a) Moore^s test. A positive result is obtained. 



(6) Trommefs test. A positive result is obtained. 



(f) Fehling's test. Eeduction takes i)lace. 



{d) OsQ,zone test. Note that the crystals are identical with those formed from 

 glucose. 



(e) a-Naphthol test (see p. 44). A strong reaction is given. 



(/) Seliwanoff's test. To 5 c.c. of Seliwanoffs solution (prepared \>y dissolving 

 0'05 gm. of resorcinol in 100 c.c. of 1 in 2 hydrochloric acid) add a few drops of 

 laevulose solution and boil. A red coloration and a red precipitate are formed. Add 

 a little alcohol and the precipitate forms a red solution. 



DlSACCHARIDES. 



These sugars are formed from the monosaccharides by condensation 

 with elimination of water. By boiling with dilute acids, or by the 

 action of certain enz-ymes, they are hydrolyzed into monosaccharides. 

 The two most important disaccharides found in plants are maltose and 

 cane-sugar. 



Maltose. Maltose or malt-sugar, though it probably occurs in smaller 

 quantities than glucose and laevulose, is widely distributed in plant 

 tissues. It is formed in the hydrolysis of starch, and its relationships in 

 the plant to starch and to other sugars will be considered later. It is a 

 white crystalline substance soluble in water and alcohol. In constitution 

 it is a glucose-a-glucoside : 



C,iHiiO.^— O— C— H 

 I 



It reduces Fehling's solution ; but less readily than glucose. With 

 phenylhydrazine hydrochloride and sodium acetate it forms an osazone 



4—2 



