OSMOTIC PRESSURE OF THE URINE. 643 



potassium oxalate and immediately titrated with N/10 caustic soda 



with constant shaking until a pronounced pale-rose color appears. 



VOZARIK 1 titrates the diluted urine without the addition of oxalate 

 and uses phenolphthalein as indicator. 



The acidity, as determined by titration, varies considerably under 

 physiological conditions, but calculated as hydrochloric acid it amounts 

 in man to about 1.5-2.3 grams in the twenty-four hours. 



By titration we learn the amount of hydrogen present which can 

 be substituted by a metal, i.e., the acidity in the ordinary older sense, 

 but not the true acidity, the ion acidity, which is given by the concentra- 

 tion of the hydrogen ions of the urine. For similar reasons, as previously 

 indicated in treating of the alkalinity of the blood-serum (page 264), 

 the ion acidity cannot be determined by titration, while it can be deter- 

 mined according to the principle of the electrometric gas-chain method 

 as there given. Such estimations have been made by v. RHORER and by 

 HoBER. 2 For normal urine v. RHORER found as a minimum 4X10~ 7 , 

 as a maximum 76X10" 7 , and as an average 30X10" 7 . HOBER found 

 4.7X10" 7 , 100X10" 7 , and 49 X 10 ~ 7 , respectively. On an average the 

 urine therefore contains 30-50 grams of hydrogen ions in 10 million 

 liters, and as in the same quantity of purest water there is contained in 

 round numbers 1 gram of hydrogen ions, the urine contains, therefore,. 

 30-50 times as many hydrogen ions as the water. From HOBER'S 

 investigations it also follows that no direct relation exists between 

 the titration acidity and the ion acidity, and that the extent of these 

 two acidities may be independent of each other. 



The osmotic pressure of the urine varies considerably even under 

 physiological conditions. The limit for the freezing-point depression 

 has been found by a number of investigators to be J= 0.87-2. 71 C. 3 

 After partaking of considerable water it may be markedly lower, and on 

 diminished supply of water it may be considerably higher. 



According to BUGARSKY a certain relation exists between the freezing- 



d 



point depression and the specific gravity, namely, T = constant = 75. This 



s 1 



equation, where s represents the specific gravity, has no general application, and 

 according to STEYRER 4 is only approximate for normal urines. The validity 

 of the relation found by BUGARSKY between the electrical conductivity and 

 the ash content of the urine, seems also to require further proof. 



1 In regard to the degree of acidity and its estimation see Naegeli, Zeitschr. f. 

 physiol. Chem., 30; Hoter, Hofmeister's Beitrage, 3; Folin, Amer. Journ. of Physiol., 

 9; Vozarik, 1. c.; de Jager, Zeitschr. f. physiol. Chem., 55, and Ringer, ibid., 60. 



2 v. Rhorer, Pfliiger's Arch., 86; Hober, 1. c. See also Jolles, Bioch. Zeitschr., 13. 



3 See Strauss, Zeitschr. f. klin. Med., 47. 



4 Bugarsky, Pfliiger's Arch., 68; Steyer, Hofmeister's Beitrage, 2. 



