GASTRIC ANALYSIS 173 



Permit the ether to separate, then allow all the fluid to run out of the separatory 

 funnel except the upper 5 c.c. of ether. To this ether extract add 20 c.c. distilled 

 water and 2 drops of a 10 per cent solution of ferric chloride and shake the mix- 

 ture gently. A slight green color is obtained in the presence of 0.05 per cent lac- 

 tic acid whereas o.i per cent lactic acid yields a very intense yellowish-green color. 



2. Ferric Chloride Test (Kelling). Fill a test-tube with water, add 1-2 

 drops of a 10 per cent solution of ferric chloride and mix thoroughly to form a 

 liquid which is very faintly colored. Divide the solution into two parts and keep 

 one part as a control. To the other part add a small amount of the strained 

 gastric contents and to the control tube add a similar volume of water. Lactic 

 acid is indicated by the immediate development of a distinct yellow color in the 

 tube containing the gastric contents. 



The color in this test is due to the formation of ferric lactate. 



3. Uffelmann's Reaction. To 5 c.c. of Uffelmann's reagent 1 in a test-tube 

 add an equal volume of strained gastric juice. A canary yellow or greenish- 

 yellow color develops if lactic acid be present to the extent of o.oi per cent or over. 



Other organic acid gives a similar reaction. Mineral acids such as 

 hydrochloric acid discharge the blue coloration leaving a colorless 

 solution. In other words, the color of the reagent is weakened in the 

 presence of an acid reaction. 



4. Hopkins' Thiophene Reaction. Place about 5 c.c. of concentrated sulphuric 

 acid in a test-tube and add i drop of a saturated solution of copper sulphate. 3 

 Introduce a few drops of the gastric contents, shake the tube well, and immerse it 

 in the boiling water of a beaker-water-bath for one or two minutes. Now remove 

 the tube, cool it under running water, add 2-3 drops of a dilute alcoholic solution 8 

 of thiophene, C4H 4 S, from a pipette, replace the tube in the beaker and carefully 

 observe any color change which may occur. Lactic acid is indicated by the ap- 

 pearance of a bright cherry-red color which forms rapidly. This color may be made 

 more or less permanent by cooling the tube as soon as the color is produced. Ex- 

 cess of thiophene produces a deep yellow or brown color with sulphuric acid. The 

 test is not wholly specific though the author claims it to be more so than Uffelmann's 

 reaction. 



(f) Detection of Occult Blood. 4 i. Ortho-tolidin Test (Ruttan and Hardisty). 5 

 To i c.c. of a 4 per cent glacial acetic acid solution of o-tolidin 6 in a test-tube add 

 i c.c. of the gastric juice under examination and i c.c. of 3 per cent hydrogen 

 peroxide. In the presence of blood a bluish color develops (sometimes rather 

 slowly) and persists for some time (several hours in some instances). 



1 Uffelmann's reagent is prepared by adding ferric chloride solution to a i per cent solu- 

 tion of carbolic acid until an amethyst-blue color is obtained, due in part to the formation of 

 a ferric salt of carbolic acid and in part to the reduction of some of the iron. 



2 This is added to catalyze the oxidation which follows. 



3 About 10-20 drops in 100 c.c. of 95 per cent alcohol. 



4 These tests may be made upon the strained stomach contents or upon the solid residue. 

 6 Ruttan and Hardisty: Canadian Medicine Ass'n Journal, Nov., 1912; also Biochem. 



Bull., 2, 225, 1913. 



NH 2 NH 2 



CH CH, 



