66 THE SALTS OF THE PLASMA AND SERUM. [BOOK I. 



THE SALTS OF THE PLASMA AND SERUM. 



When an organic liquid such as the plasma, the serum, or the 

 blood, is evaporated to dryness, and the dry residue is exposed to a red 

 heat in a crucible, the organic matters are oxidized and the products 

 of oxidation escape, leaving the inorganic or mineral matters behind. 

 We cannot, however, suppose that even the whole of the inorganic 

 matters originally present in the liquid can be obtained in this 

 way, for, however carefully we may proceed, there will always be more 

 or less volatilization of certain saline constituents as, for instance, of 

 sodium chloride. Still less are we justified in concluding from the 

 inorganic compounds left in the ash after the most cautious ignition, 

 that the same compounds were originally present in the liquid, for 

 they may only have been produced under the action of heat, and 

 at the expense of some constituents of organic bodies. We must 

 bear these considerations in mind in our judgment of the results 

 of analyses of the ashes of plasma and serum. 



Much more reliable, however, is the information furnished us by 

 the direct precipitation of the inorganic constituents of the serum by 

 the addition of certain reagents to it. Under the direction of Ludwig, 

 Pribram 1 and Gerlach 2 have directly determined the amount of 

 calcium, magnesium, and phosphoric acid in the serum by a method 

 which will be found described in Chapter IV., and it is upon 

 their results that are alone based any accurate conclusions as to these 

 three constituents of the serum. 



The following facts may be taken as resting upon a firm foundation. 



1. The serum contains a somewhat smaller proportion of 

 inorganic salts than the liquor sanguinis, some being carried down 

 with, or perhaps more intimately associated with, the fibrin when it 

 separates. 



2. The amount of inorganic matter left on the cautious ignition 

 of serum amounts to from 0'7 to 0'9 per cent. 



3. The principal inorganic constituent of the ash of plasma and 

 serum, and not only of the ash, but of the liquids themselves, is 

 common salt, sodium chloride, NaCl; the amount present in the 

 liquid being about 0'5 per cent. 



This salt constitutes, according to Lehmann, 61 per cent, and 

 according to Schmidt 65*2 per cent, of the ash left by serum. That 

 it is present before ignition is easily proved by the fact that crystals 

 of salt separate on concentrating serum. 



4. In addition to sodium chloride, the ash of plasma and serum 

 contains, as its next most abundant ingredient, sodium carbonate. 



It appears probable that the plasma and the serum before 

 ignition contain not sodium carbonate Na 2 CO 3 , but sodium hydric 



1 Pribram, "Eine neue Methode zur Bestimmung des Kalkes und der Phosphorsaure 

 im Blutserum." Ludwig's Arbeiten, 1871. 



2 Gerlaeh, "Ueber die Bestimmung der Minerale des Blutserums durch directe 

 Fallung." Ludwig's Arbeiten, 1872. 



