520 AS AMERICAS TEXT-BOOK OF PHYSIOLOGY. 



Potassium Phosphates. — The primary (K H 2 PG 4 ) and secondary (K 2 HP0 4 ) 

 phosphate of potassium are the principal .silts <>f the cells of the body, and are 

 likewise present in the urine, and to a very small extent in the blood-plasma. 

 They are undoubtedly intimately connected with the functional activity of proto- 

 plasm. Presence of carbonic acid causes the conversion of the secondary phos- 

 phate into the primary salt, and this occurs in the blood-corpuscle as well as in the 

 plasma : 



K 2 HP< ) 4 + C< ) 2 + H 2 = KH 2 P0 4 + KHCO3. 



Primary acid phosphate of potassium contributes to the acid reaction of the 

 urine, though in presence of .-odium chloride there is a tendency to the forma- 

 tion of primary sodium phosphate and potassium chloride. It is the cause of 

 the acid reaction in muscle in rigor mortis (see p. 546). 



Potassium Carbonates. — The primary and secondary carbonates exist 

 in the body only in trifling quantities. They may be produced as above de- 

 scribed by the action of carbonic acid on the phosphates, they may be ingested 

 with the food, or they may result in the body from the combustion of an organic 

 salt of potassium, according to the same reaction as would take place by burn- 

 ing it in the laboratory, 



KAH 4 O fl + 50 = K 2 CO s + 3C0 2 + 2H 2 0. 



K tartrate. 

 Feeding potassium carbonate or an organic salt of potassium makes the urine 

 alkaline owing to the excretion of potassium carbonate. 



Potassium salts are poisonous if introduced into the blood in too large quantities. In 

 concentrated solutions in the stomach the} 7 produce gastritis, even with quickly fatal 

 results.' 



Zuntz believes that potassium is combined with haemoglobin in the blood-corpuscle, and 

 may be dissociated from it by the action of carbonic oxide. 2 



Potassium in the Body. — The various salts of potassium are received 

 with the food in the manner described ; the phosphate may be retained for 

 new tissue, but the other salts are removed in the urine. They are all quite 

 completely absorbed in the intestinal tract. In starvation, or in fever, where 

 there is high tissue-metabolism, the body suffers greater loss of the potassium 

 phosphate-containing tissue than it does of the sodium-rich blood, and potas- 

 sium exceeds sodium in the urine (reverse of the usual proportion); also 

 milk, which is prepared from tissue, contains more potassium than sodium. 

 Bunge 3 has noted an important influence of potassium salts. If a potassium 

 sail be in solution together with .-odium chloride, the two partially react on 

 each other, with formation of potassium chloride. If now potassium carbon- 

 ate, for example, be eaten, the same reaction occurs in the body, 



K 2 ( !< >, + 2Na< 11 = 2KC1 + Na 2 C0 3 . 



The kidney has the power of removing soluble substances which do not belong 

 to the blood or are present in it to excess, and consequently the two salts 



1 Bunge: Physiologiache CKemie, 3d ed., 1894, S. 136. 



s A. Loewy und X. Zuntz: Pfluger'i ArcMv, 1894, Bd. 58, S. 522. :; Op. cit., S. 108. 



