Gastric Antacids 



437 



The ideal gastric antacid would appear to be a substance which 

 can neutralize hydrochloric acid but cannot make the stomach 

 alkaline and which is excreted, unchanged, in the intestine and 

 not in the urine. Such substances are found in the secondary 

 and tertiary phosphates of calcium and magnesium. They are 

 neutral substances, which dissolve in the hydrochloric acid of 

 the stomach with the formation of the corresponding acid phos- 

 phates; An excess cannot quite alkalinize the stomach. The ter- 

 tiary phosphates, as was shown by the work of Steel and Gies 1 

 and of Lothrop 2 for bone-ash, which is very nearly pure 

 Ca 3 (P0 4 ) 2 , and by experiments of the author (see Table I) for 

 Mg 3 (P0 4 ) 2 , are precipitated in the intestine and eliminated in the 

 stool. Dogs have received bone-ash, in many times the thera- 

 peutic dose, for years without apparent ill effect. 



TABLE L 



Effect of ingestion of magnesium phosphate on urinary excretion. Subject G., 

 weight 71 kilos; constant diet, including 1000 c.c. milk daily. 



N 



P 



Ca 



Mg 



grams. 



grams. 



grams. 



grams. 



13.50 



1.28 



0.253 



0.121 



11.20 



1.00 



0.326 



0.156 



13.44 



1.25 



0.264 



0.131 



12.03 



1.40 



0.159 



0.161 



12.68 



1.25 



0.182 



0.187 



grams Mg 3 (P0 4 ) 2 

 0.88 gm. Mg) 

 with each of 3 meals. 



TABLE II. 



Neutralizing action of several antacids as determined by adding the amounts 

 shown to 100 c.c. of 0.555 N HC1 at 37°, stirring while at 37° for 10 

 minutes and filtering, if any remained undissolved. The filtrates were 

 used for colorimetric determination of hydrogen ion concentration and 

 for titration with Toepfer 's reagent and phenolphthalein as indicators. 

 The results are expressed in c.c. of 0.1 N NaOH required per 100 c.c and 

 as negative logarithms of hydrogen ion concentration. 



Bi 2 (OH) 4 C0 3 



Amount 

 grams. 



Toepfer. 



Phenol- 

 phthalein. 



Ph 



Toepfer. 



Phenol- 

 phthalein. 



Ph 



0.100 



53.0 



54.6 



1.30 



54.3 



56.1 



1.25 



0.200 



51.8 



52.9 



1.30 



54.0 



56.6 



1.25 



0.400 



50.5 



52.2 



1.35 



51.8 



55.9 



1.30 



1.000 



47.2 



47.9 



1.40 



47.2 



56.7 



1.70 



4.000 









20.9 



53.2 



2.00 



Neutralon 



1 M. Steel and W. J. Gies, Amer. Jr. Physiol, 1908, xx, 343. 



2 A. P. Lothrop, Amer. Jr. Physiol, 1909, xxiv, 297. 



