HANDBOOK FOR BIO-CHEMICAL LABORATORY. 75 



Jakscli, Knapp, Lowentlial, Moore, Moliscli, Mulder, Nylan- 

 der, Penzoldt, Pavy, Roberts, Rubner, Soldani, Schiff, Tram- 

 mer, Wenders. 



GMELIN'S Test (Bile Pigments). If nitric acid containing 

 some nitrous acid is carefully poured beneath a solution con- 

 taining bile pigments, a series of colored layers are obtained at 

 the juncture of the two liquids in the following order from 

 above downwards : green, blue, violet, red, and reddish yel- 

 low. The green ring must never be absent, and also the 

 reddish violet must be present at the same time, otherwise 

 the reaction may be confused with that for lutein, which gives 

 a blue or greenish ring. The nitric acid must not contain too 

 much nitrous acid, for then the reaction takes place too 

 rapidly and does not become typical. Alcohol must not be 

 present, because it gives a play of colors with the acid. 



GRIESS'S Reagent (Nitrous Acid). A solution of metadiam- 

 ido-benzol (melting at 63 C.) gives an intense yellow colora- 

 tion with dilute solutions containing nitrous acid which have 

 been acidified with a few drops sulphuric acid. 



GRIGG'S Test (Proteids). A solution of meta-phosphoric 

 acid gives a precipitate with all proteids with the exception 

 of the peptones. 



GUANIN. See Capranica. 



Test (Acetone). Add an alcoholic solution of 

 iodine to the liquid to be tested and then ammonia. On 

 standing a precipitate of iodoform and a black precipitate 

 of iodide of nitrogen is formed, but this latter gradually dis- 

 appears on standing, leaving the iodoform visible. 



GUNZBURG'S Eeagent (Hydrochloric Acid). Dissolve 2 

 grms. phloroglucin and 1 grm. vanillin in 100 c.c. alcohol. 

 In testing for the presence of free HC1 add an equal amount of 



