V] HYDROLYZING ENZYMES 59 



begin to do})Osit. Then pour into an equal volume of alcohol, and allow to statid for 

 one or two days. The crude precipitate of inulin is filtered off, dissolved in a small 

 amount of water, and reprecipitated with alcohol. It can be washed with alcohol 

 and ether and dried over sulphuric acid. 



The Artichoke (/ie^wm^i^ Its tuberosus) may also be used, about 12 tubers being- 

 necessary. 



Expt. 60. Tests for inulin. Make a solution of some of the inulin prepared in 

 Expt. 59 in hot water. It will readily dissolve giving a clear solution. With the 

 solution make the following tests : 



(«) Make a very dilute solution of iodine and add to it a dro[) or two of inulin 

 solution : the brown colour will be unaffected. 



(6) Boil some inulin solution with a little Fehling : no reduction takes place. 



If the inulin solution which is being used should reduce Fehling it indicates that 

 sugar is present as impurity. If this is the case, then a little of the solid iiuilin 

 should be washed free from sugar by means of alcohol before proceeding with the 

 following tests. 



(c) To a little inulin solution add some 1 "/„ alcoholic solution of a-naphthol and 

 a few drops of concentrated sulphuric acid and warm. A deep violet colour is 

 produced. This is due to the formation of furfural from the laevulose produced in 

 hydrolysis (see laevulose, p. 51). 



{d) To a little inulin solution add about an equal quantity of strong hydrochloric 

 acid and a few crystals of resorcin. A red coloration is formed. This reaction 

 (Seliwanoff's test) is also due to the presence of laevulose (see laevulose, p. 51). 



Expt. 61. Hydrolysis of inulin. Some inulin is dissolved in very dilute hydrochloric 

 acid (about 0-5 "/„) and heated on a water-bath for half an hour in a round-bottomed 

 flask provided with an air condenser (see p. 45). The solution is then neutralized 

 with sodium carbonate and concentrated on a water-bath. With the concentrated 

 solution make the following tests : 



(rt) Boil with a little Fehling : the solution is rapidly reduced. 



{h) Make the osazone test (see p. 49). Glucosazone crystals will be found to be 

 formed on microscopic examination. (Laevulose forms the same o.sazone as glucose.) 



(c) Make the tests (c) and {d) of the last experiment. A positive result will be 

 given in each case. 



M ANNANS. 



The mannans v^hich have already been mentioned (see p. 50) are 

 condensation products of the hexose, mannose. They occur most fre- 

 quently, either mixed, or in combination, with the condensation products 

 of other hexoses and pentoses (glucose, galactose, fructose and arabinose) 

 as galactomannans, glucomannans, fructomannans, mannocelluloses, etc. 

 Such mixtures or compounds of which mannans form a constituent are 

 widely distributed in the seeds of many plants, i.e. Palms (including the 

 Date-palm), Asparagus (Ruscus), Clover {Trifoliiun), Coffee Bean {Coffea 

 arabica), Onion (Allium Cepa) and of members of the Leguminosae, 



