260 THE BLOOD. [CH. X. 



disappeared from the tube. Of this volume a certain amount has 

 been adsorbed by the kieselgur. The remainder has formed silver 

 chloride with the chlorides of the blood. Since I cc. of N/ioo silver 

 = 0-585 mg. NaCl, the amount of NaCl in the blood taken can be 

 calculated. 



7. Example. 



Weight of blood taken = 116 mg. 



Volume of N/ioo silver adsorbed by kieselgur =0-12 cc. 



Volume of N/ioo silver required for titration = 1*21 cc. 



Volume of N/ioo silver precipitated as silver chloride 

 = i-2i - 0-12 = i -09 cc. 



NaCl in 116 mg. blood = 1-09 x 0-585 = 0-638 mg. 

 NaCl per cent. = 0-55. 



314. The estimation of the non-protein nitrogen of blood. 



Principle. Blood is treated with water and then with a solution 

 of metaphosphoric acid, which precipitates the whole of the proteins 

 (Ex. 17). An aliquot portion of the nitrate is concentrated and the 

 total nitrogen determined by Kjeldahl's method. 



Reagents and Apparatus Beguiled. 



1. The usual requisites for Kjeldahl's method (see p. 322). 



2. Freshly prepared solution of metaphosphoric acid. Weigh out 

 2 -5 grams, of " glacial phosphoric acid," and crush it in a mortar with 8 cc. of 

 distilled water. 



3. The apparatus shewn in fig. 34. A is a wash bottle containing I in 5 

 sulphuric acid, to remove ammonia from the air. 



B. A large boiling tube (9 x j"\ in.). 



C. A funnel, with tap and side piece, as shewn. 

 E. A plain condenser. 



G. A boiling-tube (10 x ij in.), with the flange ground off on a wet stone. 

 The tubes B and G and the inner tube of E must be of resistance glass. 



4. A micro-burner, or, better, an ordinary Bunsen fitted with a 

 rose- top. 



5. A foot bellows or a blast pump to enable the final titration to be 

 conducted in a CO 2 -free atmosphere. The air is led through wash bottles 

 containing i in 4 sulphuric acid (to remove ammonia) and then through soda 

 (to remove the CO 2 ). It then passes to a thick- walled tube, which is bent to 

 fit the tube G, as shewn in fig. 35. 



