176 



DETERMINATION OF WATER, SOLIDS, AND ASH. [BOOK I. 



Knowing the weight of equal volumes of water and blood at the same 

 temperature we can at once get the density as before by dividing the 

 latter by the former : 



TABLE OF THE DENSITY OF WATER AT TEMPERATURES BETWEEN 



AND 30 C. 



Determination of the Reaction of Blood. 



As was stated at p. 26, the reaction of blood cannot be accurately 

 ascertained by immersing into it ordinary test-papers, but by following 

 one of the methods suggested by Kuhne, Zuntz, or Liebreich. With 

 the aid of one of these methods the amount of a standard acid re- 



?uired to neutralize a given volume of blood may be determined, 

 t is essential, however, to employ a carefully prepared solution of 

 litmus, free from alkali. With this object 16 grammes of com- 

 mercial litmus are finely pulverized, and the powder is mixed in a 

 beaker with 120 c.c. of water and frequently stirred. After 24 hours 

 the solution, which contains nearly all the free alkali of the litmus, is 

 thrown away and the residual litmus is again treated with 120 c.c. 

 of water for 24 hours. The solution thus obtained is divided into 

 two equal portions ; the one is carefully treated with a little 

 very dilute acid, added by means of a glass rod, until a red tint 

 just appears, and then to this is added some of the other portion, 

 until a little of the fluid, when much diluted, presents a blue- 

 violet colour. . 





