60 CARBOHYDRATES [ch. 



left which should be extracted with a little hot alcohol and then reserved for the next 

 experiment To show the presence of maltose, the combined alcoholic extracts are 

 evaporated to dryness on a water-bath, the residue taken up in a little water and the 

 osazone test made (see p. 50) with the solution. Crystals of maltosazone will separate 

 out. 



(6) By diastase from germinating Barley (Hordeum vulgare). Weigh out about 

 25 gms. of barley grains and allow them to germinate by soaking and spreading on 

 damp blotting-paper for 5-7 days. Pound the grains well in a mortar, add 100 c.c. of 

 water, allow to stand for 2-3 hrs. and filter. Precipitate the filtrate with alcohol and 

 allow to stand for 24 hrs. Filter off the precipitate, take up in water and add it to 

 the barley starch "solution," together with a few drops of chloroform. Proceed as 

 with {a) only the time for hydrolysis may be much shorter, i.e. 6-12 hrs. 



Expt. 58. Tests for dextrin. Make a solution of the dextrin prepared in the last 

 experiment (or use commercial dextrin) and note that it is very soluble in water. With 

 the solution make the following tests : 



{a) Add a little iodine solution. If erythrodextrin is present, a reddish-brown 

 colour is produced. Heat the solution and the colour will disappear. Cool again and 

 the colour will reappear. If only achroodextrin is present, no colour will be given 

 with iodine. 



(6) Add an equal volume of strong alcohol. The dextrin is precipitated. 



(c) Add an equal volume of saturated ammonium sulphate solution, i.e. half 

 saturation with ammonium sulphate. The dextrin is not precipitated. 



id) Add some basic lead acetate solution : the dextrin is not precipitated. 



Inulin. 



Inulin. This substance occurs as a soluble " reserve material " in the 

 cell-sap of the underground stems, roots and also leaves of a number of 

 plants, especially members of the Compositae, e.g. Dahlia {Dahlia varia- 

 hilis), Jerusalem Artichoke (Helianthus tuber osus), Chicory (Cichorium 

 Intyhus) and the Dandelion {Taraxacum officinale). It is said to occur 

 also in the Campanulaceae, Lobeliaceae, Goodeniaceae, Violaceae and 

 many Monocotyledons {Hyadnthus, Iris, Muscari and Scilla). 



Inulin is a condensation product of laevulose to which it bears much 

 the same relation as starch to glucose. It is a white substance, soluble 

 in water and insoluble in alcohol. It crystallizes out in the cells, in which 

 it occurs, in characteristic sphaero-crystals on addition of alcohol to the 

 tissues. It is hydrolyzed by mineral acids to laevulose : also by the 

 enzyme inulase which occurs in the plant. 



£Jxpt. 59. Extraction of inulin. Cut off the tubers from two Dahlia (Dahlia 

 variabilis) plants, wash well, and put them through a mincing machine. Carefully 

 collect the liquid and the crushed tuber, and boil well with sufficient water to cover 

 the crushed material. Add also some precipitated calcium carbonate to neutralize 

 any free acids present. Then filter through fine muslin, and to the filtrate, which 

 should again be made quite hot, add lead acetate solution until a precipitate 



