GASTRIC ANALYSIS 177 



according to the directions given below. The volume of fluid present in the stomach 

 one hour after an Ewald meal varies under normal conditions between 50 and 100 

 c.c. In cases of hypersecretion or defective motility 200-300 c.c. may be found. 

 Very excessive volumes, e.g., 500-3000 c.c., are indicative of dilatation of the 

 stomach and suggest pyloric stenosis, either benign or malignant. 



i. Total Acidity. 1 Add 3 drops of a i per cent alcoholic solution of phenol- 

 phthalein 2 to the contents of vessel A and titrate with N/io sodium hydroxide solu- 

 tion until Si faint pink color is produced and persists for almost two minutes. Take 

 the burette reading and calculate the total acidity. 



Calculation. The total acidity may be expressed in the following ways: 



1. The number of cubic centimeters of N/io sodium hydroxide solution neces- 

 sary to neutralize 100 c.c. of gastric juice. 



2. The weight (in grams) of sodium hydroxide necessary to neutralize 100 c.c. 

 of gastric juice. 



3. The weight (in grams) of hydrochloric acid which the total acidity of 100 

 c.c. of gastric juice represents, i.e., percentage of hydrochloric acid. 



The forms of expression most frequently employer! are i and 3, preference being 

 given to the former, particularly in clinical work. 



In making the calculation note the number of cubic centimeters of N/io sodium 

 hydroxide required to neutralize 10 c.c. of the gastric juice and multiply it by 10 to 

 obtain the number of cubic centimeters necessary to neutralize 100 c.c. of the fluid. 

 If it is desired to express the acidity of 100 c.c. of gastric juice in terms of hydro- 

 chloric acid, by weight, multiply the value just obtained by 0.00365.* 



2. Free Acidity (Organic and Inorganic). Add 3 drops of sodium alizarin 

 sulphonate solution 4 to the contents of vessel B and tirate with N/io sodium hy- 

 droxide solution until a violet color is produqed. In this titration the red color, 

 which appears after the tinge of yellow due to the addition of the indicator has 

 disappeared, must be entirely replaced by a distinct violet color. Take the burette 

 reading and calculate the free acidity due to organic and inorganic acids. 



Calculation. Since the indicator used reacts to both organic and inorganic 

 acids, the number of cubic centimeters of N/io sodium hydroxide used indicates 

 the free acidity of 10 c.c. of gastric juice. The data for 100 c.c. of gastric juice may 

 be calculated according to the directions given under Total Acidity, page 166. 



3. Free Hydrochloric Acid. 5 Add 4 drops of di-methyl-amino-azobenzene 

 (Topfer's reagent) solution 6 to the contents of the vessel C and titrate with N/io 

 sodium hydroxide solution until the initial red color is replaced by orange yellow. 1 

 Take the burette reading and calculate the free acidity. 



Calculation. The indicator used reacts only to free hydrochloric acid, hence the 

 number of cubic centimeters of N/io sodium hydroxide used indicates the volume 

 necessary to neutralize the free hydrochloric .acid of 10 c.c. of gastric juice. To 

 determine the data for 100 c.c. of gastric juice proceed according to the directions 

 given under Total Acidity, page 165. 



1 This includes free and combined acid and acid salts. 



2 One gram of phenolphthalein dissolved in 100 c.c. of 95 per cent alcohol. 



3 One c.c. of N/io hydrochloric acid contains 0.00365 gram of hydrochloric acid. 



4 One gram of sodium alizarin sulphonate dissolved in 100 c.c. of water. 



5 Hydrochloric acid not combined with protein material. 



6 One-half gram dissolved in 100 c.c. of 95 per cent alcohol. 



7 If the orange yellow color appears as soon as the indicator is added it denotes the ab- 

 sence of free acid. 



