164 



PHYSIOLOGICAL CHEMISTRY 



(b) Determination of Free Acidity. The reagent most widely used, 

 clinically, for the determination of free hydrochloric acid in stomach 



Total acidity 



I 



3 



80 



60 



40 





Free acidity 



to Vz */4 i 1'A V/z 1V4 2 hours 



FIG. 46. ACIDITY CURVES FROM A CASE OP HYPERACIDITY. 



contents is Topfer's reagent (see page 175). It has been found, however, 

 that this reagent gives rather inaccurate results due to the uncertain 



FIG. 47. ACIDITY AND PROTEIN CURVES IN GASTRIC CARCINOMA. (Clarke and Rehfuss: 

 Jour. Am. Med. Ass'n, 64, 1737, 1915.) 



end point. For this reason we have employed Sahli's reagent. 1 This 

 reagent contains KI and KIOs and liberates iodine in the presence of 



1 A mixture of equal parts of a 48 per cent solution of potassium iodide and an 8 per cent 

 solution of potassium iodate. 



