APPENDIX 393 



Filter the gastric contents and test first for free HC1. The most reliable and 

 sensitive test is that of Gunsberg. The reagent, which should be freshly prepared, 

 consists of phloroglucin 3 grams, vanillin i gram, and absolute alcohol 30 c.c. By 

 mixing 2 drops of gastric juice and an equal quantity of Gunsberg reagent in a small 

 porcelain dish and carefully heating above a flame we obtain a carmine red color 

 if free HC1 be present. A water bath is preferable. 



For lactic acid a modification of Strauss' method is quite satisfactory. Shake, 

 in a test-tube, 5 c.c. of gastric contents with 20 c.c. of ether, allow to settle and 

 pour off 5 c.c. of the supernatant ether into another test-tube. To this ether add 

 20 c.c. of water and 2 drops of a i to 9 solution of ferric chloride and shake well. 

 The presence of i% of lactic acid will give an intense greenish color. 



Having determined the presence or absence of free hydrochloric or lactic acid, 

 we should make a quantitative test of the various factors producing the acidity of 

 gastric juice (a modified Topfer test). These are: i. Free HC1. 2. Combined HC1. 

 3. Acid salts, and 4. Total acidity. 



To 10 c.c. of filtered gastric contents, in a beaker, add 3 drops of dimethyl- 

 amido-azo-benzol solution (a 1/2% solution in 95% alcohol). In the presence of 

 free HC1 the fluid becomes a rich carmine pink. 



After reading the burette run in N/io NaOH solution until the pink color is 

 discharged and a light yellow color is obtained. This reading multiplied by 10 

 gives the amount of free HC1 in degrees, a degree corresponding to i c.c. N/io 

 NaOH. Next add 6 drops of a 1/2% alcoholic solution of phenolphthalein to the 

 light yellow fluid in the beaker. Again titrating the same preparations we add 

 N/io NaOH until a faint but distinct pink color is produced. The number of c.c. 

 added for the free HC1 plus the number to give the pink color when multiplied by 

 10 gives the total acidity in degrees. (For example: 2.5 c.c. N/io NaOH used to 

 obtain yellow color 2.5X10 = 25 or acidity due to free HC1. After adding the 

 phenolphthalein, 4 c.c. N/io NaOH required to produce pink color 4+2. 5 X 

 10 = 65 or total acidity in terms of acidity. This means that it would require 65 

 c.c. N/io NaOH to neutralize 100 c.c. of gastric juice. A total acidity of 60 

 is about normal. To obtain percentage in HC1 multiply by 0.00365; thus. 65 X 

 0.00365 = 0.23 HC1.) 



Having determined the total acidity add 3 c.c. of 10% neutral calcium chloride 

 solution to the gastric contents already in the beaker. As a result of the formation 

 of acid calcium phosphate the pink color is discharged. Again add N/io NaOH 

 from the burette until the pink color is restored. The number of c.c. used gives the 

 amount of acid salts present. 



From the figures for the total acidity subtract the sum of that for free HC1 and 

 for acid salts and the remainder will give the acidity due to combined HC1. 



G CHEMICAL TESTS OF FAECES. 



To test for acidity Kaplan rubs up 5 grams faeces in 30 c.c. distilled water. Put 

 2 c.c. of the emulsion in a test-tube and add a few drops of phenolphthalein solution. 

 Titrate with N/io NaOH to a pink. A normal stool from a Schmidt test-diet re- 

 quires about 1.5 c.c. N/io NaOH. After fermentation the stool may be quite acid 

 or more alkaline than before the fermentation test. 



