f39) 



of 51. G. If Instead of 0.9 calfserum 1 cc. was used llie (luanlity of liorseserum 



would necessarily liave amounted to 0,5 X r, a — ^>^^ ^^- ^^ '^^ appears that by llie 



addition of 0.3 cc. horseserum to 1 cc. calfserum the precipitate amounts to 74.1 and 

 by the addition of 0.55 cc. horseserum but to 37.3 i). 



This decrease must be attributed partly to the solubility of the 

 precipitum in NaCl-solulion, a solubility wliich is felt the more strongly 

 as a greater quantity of diluted horsescruui is added. (Compare also 

 Fol. Haematol 1. c). 



So we see that the clear liquid above the precipitate contains, 

 besides free precipitin and free precipitinogen substance, as has already 

 been slated, also dissolved precipitate. 



These three substances must form a variable ecpiilibrium, which 

 according to the rule of (xUi.dbkkg and Waacü-; is to be expressed 

 by the foUowiiig relatioii. 



Concentration of the free precipitinogen subst. X Concentr. 

 of the precipitin = ki X Concentr. of the dissolved precipitate .... (1) 



in this /(j is the constant of reaction. 



Meanwhile it appears from the experiment, that a greater quantity 

 of precipitate must be dissoh^ed than corresponds with this equation, 

 or to express it more clearly, than corresponds with the concej)tion 

 that the solubility of the precipitate in NaCl solution is the only fact 

 by which the quantity of sediment decreases. 



To take away the difüculty, the hypotiiesis was made that still 

 another portion of the precipitate forms a dissolvable compound with 

 free precipitinogen substance (of horseserum) and that we have 

 here a case analogical to the reaction of CaH._,Oj with COjj. As is 

 known CaH^O^ is precipitated by CO^, but by addition of more CO.^ 

 the sediment of CaCOj decreases again, while COj with CaCOj forms 

 a dissolvable substance. 



As will soon be seen, a very satisfactory conformity between 

 calculated and observed quantity of precipitate is obtained through 

 this hypothesis, which could afterwards be experimentally aflirmcd. 



Let us now try, reckoning both with the solubility of the precipi- 

 tate in NaOl-solution and with the forming of a dissolvable mixture 

 of precipitate with precipitinogen substance, to precise more closely 

 equation I. 



1) The hyperbolic form of the precipitate curve with ncreasing quantity of liorse- 

 serum may still appear from the following series of experiments taken on anotlier 

 day (Table 111). This series has not been used for the following calculation. 



