:} 



Blue with iodine. 



22 PRACTICAL PHYSIOLOGY. [lIL 



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

 the following is the reaction which takes place : — 



C,Hi A + 2CAIT,H3 = C,8H,,N,0, + 2H,0 + 2H. 



Phenyl-glucosazone. 



(k.) 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 '* SaHva ") : — 



Starch 



Soluble starch (amidulin or amylodextrin) 



V aneties \ Ej.ythrodextrin .... Iodine gives violet and red. 



Dextrin I ^chroodextrin No reaction with iodine. 



,, ,^ r Fehling's solution reduced. 



^al^ose i Barfoed's not. 



Dextrose Both are reduced. 



Estimation of Glucose (see " Urine "). 



10. VI. Maltose (Ci2H220ii)- — I^ forms a fine white warty 

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

 diastatic ferments on starch. See "SaUva," 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 " Sahvary digestion.") 



{c.) Boiled for ij hours with the phenyl-hydrazine test it yields 

 phenyl-maltosazone (C24H32N4O9). It crystalUses 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. 



(c.) 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. 



