22 PRACTICAL PHYSIOLOGY. [ill. 



formed is but slightly soluble in water. According to E. Fischer, 

 the following is the reaction which takes place : 



C 6 H 1 ,0 6 + 2 C 6 H 6 N 2 H 8 = C 18 H 22 N 4 4 + 2 H 2 + 2 H. 



Phenyl-glucosazone. 



(&.) Molisch's Test. (i.) To the solution add a drop or two of a 15- 20 per 

 cent, alcoholic solution of a-naphthol, and 1-2 vols. of concentrated sulphuric 

 acid. The colour which first appears is violet ; water causes a bluish- violet 

 deposit, (ii.) If, instead of the naphthol, an alcoholic solution of thymol be 

 used, a red colour is obtained. Seegen, however, points out that this re- 

 action can be obtained with other substances, e.g., albumin, which, however, 

 is denied by Molisch. It is not a reliable test. 



9. Conversion of Starch into Glucose. Boil starch solution 

 with a few drops of 20 per cent, sulphuric acid, until the fluid 

 becomes clear. After neutralising with sodium carbonate, test tho 

 fluid for glucose by the tests (6.) or (c.). 



A large number of intermediate products, however, are formed. 

 They are as follows (see also " Saliva ") : 



Soluble starch (amidulin or amylodextrin) ' .' } Blue with iodine ' 

 111 P ies } Erythrodextrin .... Iodine gives violet and red. 



Dextrin 1 Achroodextrin ..... No reaction with iodine. 



,_ ,, f Fehling's solution reduced. 



Maltose ........ ( Barfoed's not. 



Dextrose ........ Both are reduced. 



Estimation of Glucose (see " Urine "). 



10. VI. Maltose (C 12 H 2 . 2 O n ). It forms a fine white warty 

 mass of needles, and is the chief sugar formed by the action of 

 diastatic ferments on starch. See "Saliva," and "Pancreatic 

 Juice." 



(a.} Mix i gram of ground malt with ten times its volume of 

 water, and keep it at 60 C. for half an hour. Boil and filter ; the 

 filtrate contains maltose and dextrin. 



(h.) Test for a reducing sugar with Fehling's solution or other 

 suitable test. (See also " Salivary digestion.") 



(c.} Boiled for i J hours with the phenyl-hydrazine test it yields 

 phenyl-maltosazone (C 24 H 32 N 4 9 ). It crystallises in yellow 

 needles (fig. 8). 



(d.) It is soluble in water and alcohol. Examine its crystals 

 (fig. 7). Its specific rotatory power is + 150, i.e., it is greater 

 than that of dextrose, but its reducing power (on Fehling's solution) 

 is only two- thirds of that of dextrose. 



(&.} With Barfoed's reagent, i.e., when boiled with half its volume of copper 

 acetate, acidulated with acetic acid = no reduction. In this respect, and in 

 some others, it differs from dextrose. 



