Ill 



as the mixtures of toxin and antitoxin in the example 

 just mentioned. Among the mixtures of ammonia, one 

 was selected, containing 0,17 cc. o,l n NH 3 in 10 cc. 

 blood, which showed a convenient degree of colour 

 that could be exactly determined by means of the 

 colorimetric method. 



In this case theoretical reasons lead us to foresee 

 that the equation: 



(free NH 3 | (free H 3 3 B| INHJ^OgBia 



I vol J| vol j K\ vol J 

 would be right. 



If (NH 3 ) be the concentration of ammonia, (H 2 O) be 

 the vapour-pressure of the water in the solution, which, 

 in these exceedingly small concentrations without recog- 

 nizable error, can be considered as constant (the total 

 concentration amounts in maximo to 0,025 normal, cor- 

 responding to a decrease of the vapour-pressure of only 

 Y 22 percent) - - is (H 3 3 B) the concentration of the boracic 

 acid etc., then the following equations are valid: 



(H 3 N) (H 3 0) - K (NH 4 OH) = K, (NH 4 ) (OH) 

 (H 3 3 B) = . K 2 (H) (H 2 3 B) 



from this follows: 



(H 3 N) (H 3 3 B) - K 3 (NH 4 ) (H 2 3 B) 



it is: the product of the concentration of the undisso- 

 ciated ammonia (not combined as salt) with the con- 

 centration of the free boracic acid is proportionate to 

 the product of the concentrations of the ions of NH 4 

 and H 2 3 B. If the amount of boracic acid be not too 

 small for a recognizable amount of borate to be form- 

 ed, then the quantity of NH 4 and H ;i O 3 B ions, 

 which may not be considered as arising from disso- 



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