. Essentials of laboratory diagnosis; designed for students and practitioners. d with the saliva. The physiologic presence of lactic acid during the first stageof gastric digestion may be due either to its formation withinthe stomach, or from its having been introduced with the food,as in baked bread. Ufflemans Test for Lactic Acid.—The addition of afew drops of filtered gastric contents to ITfnemans reagent (seeAppendix) in a test-tube will, in the presence of lactic the amethyst-blue to a canary-yellow. This test is posi-tive in the presence of 1 part of lactic acid in 20,000. So
. Essentials of laboratory diagnosis; designed for students and practitioners. d with the saliva. The physiologic presence of lactic acid during the first stageof gastric digestion may be due either to its formation withinthe stomach, or from its having been introduced with the food,as in baked bread. Ufflemans Test for Lactic Acid.—The addition of afew drops of filtered gastric contents to ITfnemans reagent (seeAppendix) in a test-tube will, in the presence of lactic the amethyst-blue to a canary-yellow. This test is posi-tive in the presence of 1 part of lactic acid in 20,000. Sources of Error.—Lactates cause the same reaction. Thisis, however, immaterial, since we desire to recognize lactic acid, DETERMINATION OF ORGANIC ACIDS. 183 whether free or combined. The reaction also takes place withalcohol, sugar, and certain salts, particularly the phosphates, butrarely in their usual concentration after the test-breakfast. Stkausss Method for Lactic Acid.—This method is, per-haps, the very best clinical method at our disposal, as it shows -rar. Fig. 36.—Strausss Separatory Funnel. lactic acid when present in pathologic amounts. It does not,however, give a quantitative result, nor does this seem necessaryin the ordinary clinical work. Into a special separatory funnel(see Fig. 36) are introduced 5 cubic centimeters of the gastricjuice. The funnel is then filled to the 25 cubic centimetermark with alcohol-free ether and well shaken. The ethereallayer will take up the lactic acid from the gastric contents. Afterthe fluids have settled, the gastric juice and ether are allowed to 184 DETERMINATION OF FUNCTIONS OF STOMACH. run out to the mark 5 by opening the stop-cock, after which dis-tilled water is added to make up the 25 cubic centimeter drops of 10 per cent, ferric chlorid solution are then addedwith a medicine dropper and the mixture well shaken. Thewater will now extract the lactic acid from the ether. Theaqueous layer is colored an i
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