462 APPENDIX 



Reaction. Urine may be quite acid in acidosis. The reaction of the mixed 

 twenty-four-hour excretions is acid to litmus. At times during this period, especi- 

 ally after meals, the reaction may be alkaline. It is not positively known to 

 what the acidity is due, some authorities considering it due to sodium dihydro- 

 gen phosphate, while others attribute it to organic acids. The acidity being very 

 largely due to food, naturally it would vary in health, as the nature of food varies. 

 The degree of acidity under normal conditions is such that from 40 to 60 c.c. of 

 N/i alkali will be required to neutralize the twenty-four-hour excretion. 



The acidity can be determined by measuring 25 c.c. of sample into beaker, adding 

 75 c.c. of distilled water, and also, if available, 10 grams of neutral potassium oxalate 

 and finally 3 or 4 drops of phenolphthalein From a burette add N/io sodium 

 hydrate until a permanent faint red or pink color is obtained. High-colored urines 

 must be diluted with more than 75 c.c. of water before the end reaction can 

 readily be detected. Normally, 6 to 8 c.c. neutralizes 25 c.c. urine. 



Formalin Method for the Estimation of Ammonia 



Free ammonia reacts with formalin to form hexamethylenetetramine. If sodium 

 hydrate is added to neutralized urine in the presence of formalin free ammonia 

 is liberated and reacts with the formalin. So soon as all the ammonia has been 

 liberated, the end reaction occurs. 



Ronchese first utilized this principle and Mathison found that potassium oxalate 

 made the end reaction sharper. Brown found that preliminary clearing with 

 lead subacetate made the end reaction still sharper and removed certain nitrogenous 

 substances which reacted with formalin making the result only about 5% higher 

 than with Schaffer's method. The technic is as follows: About 60 c.c. of filtered 

 urine are treated with 3 grams of basic lead acetate, well stirred, allowed to stand 

 a few minutes and filtered. The filtrate is treated with 2 grams of neutral potas- 

 sium oxalate well stirred and filtered; 10 c.c. of the clear filtrate are diluted to 50 

 c.c. with distilled water; a few drops of i% phenolphthalein solution are added. 

 The mixture will be slightly alkaline or acid. Five grams potassium oxalate 

 are added and stirred. It is exactly neutralized with decinormal NaOH or H 2 SO4. 

 Twenty c.c. of 20% conmercial formalin, previously made neutral, are added, and 

 the solution again titrated with decinormal NaOH to neutralization. Every cubic 

 centimeter of decinormal NaOH corresponds to 0.0017 gram NH 8 . The quantity 

 of ammonia is then calculated on the basis of the twenty-four-hour volume. 

 Example: The 10 c.c. of urine required 4 c.c. N/io NaOH to give a pink color. 

 4X0.0017 = 0.0068. Then 100 c.c. urine would contain 0.068 and 1000 c.c. 

 (twenty-four-hour urine amount) 0.68 gram of ammonia. 



ESTIMATION OF TOTAL NITROGEN 



Principle. The nitrogenous material of the urine is converted into ammonium 

 sulphate on boiling with H 2 SO<. The ammonia is then estimated as described 

 under estimation of ammonia by the formalin method. 



Technic. Solutions required: 



i. Twenty per cent, commercial formalin previously made neutral with NaOH. 



