CH. IV.] GLUTAMINIC ACID. 79 



B. Recrystallisation of the hydrochloride. 



(i.) Dissolve the crystals in about 100 cc. of water, boil with a 

 sufficiency of decolourising charcoal, and filter. 



(ii.) Saturate the cooled filtrate with dry hydrochloric acid gas, 

 and allow to stand in the ice chest over-night. 



(iii.) Add an equal volume of ice cold absolute alcohol and filter 

 through linen on a Buchner funnel. 



(iv.) Dry in a vacuum desiccator over potash and sulphuric acid, 



C. Preparation of glutaminic acid from the hydrochloride. 



(i.) Weigh the pure, dry, hydrochloride and dissolve it in a 

 minimal amount of water. Add 5-44 cc. of N.NaOH for 

 every gram, this being the amount required to remove 

 the HCl according to the following equation. 



HC1 



CH.(NH 2 ).COOH CH(NH 2 ).COOH 



+ NaOH = | + NaCl+H 2 O. 



CH 2 .CH 2 .COOH CH 2 .CH 2 COOH 



(ii.) Evaporate the solution in vacuo at 40 to 50 to reduce the 



volume to 60 to 100 cc. 





 (iii.) Transfer the warm solution to a beaker, and allow it to 



stand over-night in the ice chest. 



(iv.) Filter off the crystals on a Buchner, wash with a little cold 

 water, and dry. 



Yield : 18 to 20 grams. 



Properties of Glutaminic Acid. It crystallises from 

 water in rhombic tetrahedra, which on rapid heating 

 melt at 2 1 3. It dissolves in about 100 parts of cold water, 

 but is much less soluble in alcohol. Since it contains two 

 carboxyl and only one amino-group, its aqueous solutions 

 are markedly acid to litmus. The hydrochloride forms 



