(41 ) 



Firstly we shall, try to find an expression for the three substances 

 occurring in the clear liquid which stands above the precipitate : for 

 the free precipitinogen substance, for the free precipitin which it 

 contains and for the quantity of dissolved precipitate. 



Firstly the quantity of free prcliniinogen substance. Let A be the 

 total quantity of that substance used for an experintient. To determine 

 how much of this is still present in the li([uid in free stale, it is to 

 be determined how much is bound. Bound is : 



1. a certain quantum to form the j)recipitate which is present in 

 solid condition. If we set down as a rule that 1 mol. pi'ecipitum 

 proceeds from 1 mol. precipitinogen substance -And 1 uiul. precipitin, 

 then the wanted precipitinogen substance will be expressed by P, if 

 the molecular quantity precipitate also amounts to P. 



2. a quantity /; F when p represents the percentage of the quantity 

 of dissolved precipitate and V the total volume of the liquid. 



3. a quantity necessary to form the compound of precipitate- and 

 precipitinogen substance. Admitting that 1 mol. of this compound 

 proceeds from 1 mol precipitate and 1 mol. precii)itinogen substance 

 and then that y of this compound is present, then together 2y must 

 be charged, while in each of the two components y mol. precipitinogen 

 substance is present, so that the quantity of precipitinogen substance, 

 which is left in free state, amounts to 



A—P—pV—2y. 

 So when the volume of the liquid is V, the concentration of the 

 free precipitinogen substance =z 



A—P-pV—2y 



f ' (2) 



It is possible to calculate in the same way the concentration of 

 the free precipitin. 



If B is the total quantity of precipitin, which is used for the 

 experiment, then there is to be subtracted from this: 



l^f . a quantity P for the same reason as is given at the calcula- 

 tion of the free precipitinogen substance (see above). 



2"<^. a quantity pV, likewise as explained there. 



3'*^. a quantity necessary to form the compound precipitate-preci- 

 pitinogen substance. While in this compound but 1 mol. precipitin 

 is present, only ly is to be charged. So that the quantity of pre- 

 cipitin which remains in free state, amounts to B — P — pV — y. 



While the volume of the liquid amounts to V, the concenti'atioii 

 of the free precipitin is = 



