BINDING OF THE HYDROCHLORIC ACID 13 



different principle. An excess of relatively insoluble barium 

 oxalate is added to the gastric juice as "ground substance " 

 and the quantity of oxalic acid thrown into solution by the 

 hydrochloric acid is estimated by titration with potassium 

 permanganate. In another test 30 the amount of iodine freed 

 from a mixture of potassium iodide and potassium iodate in 

 the presence of hydrochloric acid is determined by titration 

 and used as measure of the latter. The test proposed by 

 Holmgren 31 is particularly original; it is based upon the 

 adsorption of acids in capillary media. If an acid solution 

 is allowed to drop from a pipette upon a filter paper spread 

 out horizontally it will be observed that, as the drop spreads 

 out circularly, only the central part of the moist circle shows 

 an acid reaction, the peripheral part containing nothing but 

 water. The acid moieties are thus more freely adsorbed by 

 the filter paper than the water molecules. And it has been 

 shown that the more concentrated the acid the narrower the 

 acid-free ring at the margin; and that the surface of the 

 central circular acid area and that of the peripheral acid-free 

 zone vary in relation to each other, according to the acidity 

 of the solution employed. The outcome is strikingly regu- 

 lar, and the results may be obtained almost at a glance if the 

 paper used has been colored with litmus ; and the test, car- 

 ried out in a very few moments, accords a fairly delicate esti- 

 mate for practical purposes of the acidity of a sample of 

 gastric juice. A very small quantity of the latter, about 

 one-tenth of a cubic centimeter, serves for the determination. 

 Binding of the Hydrochloric Acid by Protein Bodies. 

 There is no lack of methods, it is true, for the determina- 

 tion of the free hydrochloric acid in the gastric juice ; but 

 the question then comes up as to what can be the particular 

 value of them at best. For it must be confessed that the 

 importance of determining free hydrochloric acid, especially 



80 M. Wegrumba (Berne), Internat. Beitr. z. Pathol. u. Ther. d. Ernah- 

 rungsstorungen, 3, 53, 1911. 



* J. Holmgren (Stockholm), Deutsche med. Wochenschr., 1911, 247. 



