GASTRIC CONTENTS. 83 



tion. Carefully evaporate high over the flame. If free 

 HCl is present a rose red ring develops at margin of 

 evaporating drop. This test will determine the presence 

 of .05 parts of free HCl per mille. 



(2) To a drop of the filtrate on a porcelain capsule, 

 add a drop of the dimethyl-amido-azo-benzol solution. 

 This gives a red coloration, in the presence of free 

 HCl when present in .02 parts or over, per mille. It is 

 a more delicate test than Gunzburg's and can be used 

 to determine the amount of free HCl present. 



(e) While in practice it is found that in the presence 

 of free HCl, tests for lactic acid may be disregarded, yet 

 when free acid is present a test should be made for lac- 

 tic acid. 



Place in a graduate or test tube about 20 cc. of 

 Uffelmann's reagent. Add drop by drop from a pipette 

 the filtered stomach contents, a lemon yellow precipitate 

 falls in the presence of lactic acid. 



This test, while all that need be applied for clinical 

 purposes, is not always accurate as it is interfered with 

 by excess of HCl, presence of acetic and butyric acids, 

 alcohol or much glucose. A more satisfactory method 

 is to shake up 10 cc. of the filtrate with 30 cc. of ether, 

 repeating twice, and removing the ether with a pipette. 

 The ether is then carefully evaporated, the residue 

 extracted with water and used to make the test. 



(/) The /a% acids particularly acetic and butyric 

 acids are at times present as fermentative products. 

 The amount of these acids usually rises and falls with 

 the amount of Jactic acid. Their odor is the best quali- 

 tative test. 



