112 MALTOSE. 



maltose is boiled with Fehling's fluid 1 the amount of cuprous oxide 

 which separates out is only about two-thirds of that which would be 

 reduced by an equal weight of dextrose, or in other words 66 parts of 

 dextrose reduce as much as 100 parts of maltose. Bearing in mind 

 that maltose may be readily converted into dextrose by boiling with 

 dilute acids with a corresponding change of its optical and reducing 

 powers, while dextrose is of course unaltered by this operation, it is 

 easy to base upon the above facts a method of identifying the two 

 sugars. As a further difference between the two it may be stated that 

 Barfoed's reagent 2 is not reduced by maltose, whereas it is by dextrose 3 . 

 In this respect maltose resembles lactose (milk-sugar) which also does 

 not reduce this reagent. 



Phenyl-maltosazone. C 24 H 32 N 4 O 9 . 



This compound of maltose is obtained by the action of phenyl- 

 hydrazin upon it in presence of acetic acid in the way already described 

 (p. 104) for the preparation of the analogous compound with dextrose. 

 It crystallises readily in minute yellow needles and is characterised by 

 being (unlike phenyl-glucosazone) soluble in about 75 parts of boiling 

 water, and still more soluble in hot alcohol. Its melting point 206 is 

 practically the same as that of phenyl-glucosazone. 



The researches of Brown and Heron (see above, p. 58) showed 

 that whereas pancreatic juice rapidly converts starch-paste into maltose 

 and a little dextrose, an extract of the mucous membrane of the small 

 intestine or the tissue itself, while acting but feebly on starch-paste 

 rapidly converts maltose into dextrose. They hence surmised that 

 maltose would be found to be a non-assimilable sugar, requiring like 

 cane-sugar to be converted into the simpler dextrose before absorption. 

 More recent experiments have confirmed this view 4 , for it has been 

 found that if maltose be injected into the blood-vessels it is largely 

 excreted in an unaltered form in the urine 5 . The converting action of 

 extracts of the intestinal mucous membrane is strikingly less than that 

 of the tissue itself; from this it may perhaps be inferred that the change 

 into dextrose takes place rather during than previous to absorption. 

 This fact corresponds closely to the well-known views as to the changes 



1 Solution of hydrated cupric oxide in caustic soda in presence of the double 

 tartrate of sodium and potassium (Kochelle salt). See Soxhlet, loc. cit. 



2 Dissolve 1 part of cupric acetate in 15 parts of water : to 200 c.c. of this solution 

 add 5 c.c. of acetic acid containing 38 p.c. of glacial acid. Jn. f. pr. Chem. (2), 

 Bd. vi. (1872), S. 334. 



3 Musculus u. von Mering, loc. cit. 



4 But cf. previously Bimmermann, Pfliiger's Arch. Bd. xx. (1879), S. 201. 



5 Philips, Diss. Amsterdam, 1881. See Abst. in Maly's Bericht. 1881, p. 60. 

 See also Bourquelot, Compt. Rend. T. xcvu. (1883), pp. 1000, 1322; T. xcvni. p. 

 1604. Jaurn. de VAnat. et de la Physiol. T. xxn. (1886), p. 161. 



