952 AN AMERICAN TEXT-BOOK OF PHYSIOLOGY. 



Hydrochloric Acid, HC1, is found to a small extent in the gastric juice. 



Preparation. (1) If sunlight acts on a mixture of equal volumes of chlorine and 

 hydrogen, they unite with a loud explosion. 



(2) By the action of strong sulphuric acid on common salt, 



2NaCl + H 2 S0 4 = Na,S0 4 + 2HC1. 



(3) By the action of primary acid phosphate of sodium on common salt, 



XaH 2 PO 4 + NaCl - Na 2 HPO 4 + HC1. 



This, according to Maly, represents the process in the cells of the gastric glands. 

 Properties. Hydrochloric acid readily unites with most metals, forming 

 chlorides. It causes a gelatinization of the proteids and seems to unite with 

 them chemically. Such gelatinization is a necessary forerunner of peptic di- 

 gestion. The cleavage products of peptic digestion (peptones, proteoses, etc.) 

 combine with more hydrochloric acid than the original more complex proteid. 1 

 Hydrochloric acid of the strength of the gastric juice (0.2 per cent.) inverts 

 cane-sugar at the temperature of the body, and inhibits the action of bacteria. 

 Hydrochloric acid is indisputably derived from decomposition of chlorides in 

 the secreting cells of the stomach. It has been shown that the excretion of 

 common salt in the urine is decreased during those hours that the stomach is 

 active, while the alkalinity of the urine increases. If, in a dog with a gastric 

 fistula, the mucous membrane of the stomach be stimulated and the gastric 

 juice be removed as soon as formed, the urine becomes strongly alkaline with 

 sodium carbonate (the excess of Na liberated taking this form) while the chlo- 

 rides may entirely disappear from the urine. 2 Respiration in an atmosphere 

 containing 0.5 per cent. HC1 gas becomes very uncomfortable after twelve 

 minutes. 3 



Detection. Hydrochloric acid and the chlorides give with silver nitrate a white precipi- 

 tate of silver chloride, insoluble in nitric acid, very soluble in ammonia. If the bases 

 (K, Na, Ca, Mg, Fe) of gastric juice and then the acid radicals (Cl and P 2 5 ) be deter- 

 mined, after uniting by calculation phosphoric anhydride with the proper bases, then chlo- 

 rine with the rest of the bases, there still remains an excess of chlorine which could only 

 have belonged to hydrochloric acid present. To detect free hydrochloric acid, put three or 

 four drops of a saturated alcoholic solution of tropaeolin 00 in a small white porcelain 

 cover, add to this an equal quantity of gastric juice, evaporate slowly, and the presence 

 of hydrochloric acid is shown by a beautiful violet color, not given by any organic acid.* 

 Giinzburg's reagent consisting of phloroglucin and vanillin in alcoholic solution, warmed 

 (as above) with gastric juice containing free hydrochloric acid, gives a carmine-red 

 mirror on the porcelain, not given by an organic acid. 5 



CHLORINE IN THE BODY is ingested as chloride, and leaves the body as 

 such, principally in the urine, likewise through the sweat and tears, and in 

 traces in the feces. 



1 Chittenden : Cartwright Lectures on Digestive Proteolysis, 1895, p. 52. 



2 E. O. Schoumow-Simanowski : Archiv fur exper. Pathologic und Pharmakologie, 1894, Bd. 

 33, p. 336. 



3 Lehmann: Archiv fur Hygiene, Bd. 5, p. 1. 



4 Boas: Deutsche medidnische Wochenschrift, 1887, No. 39. 



6 Gunzburg : Centrcdblatt fur klinische Medicin, 1887, No. 40. 



