2 Art. 11.— K. Matsuno : 



Experimental 



The limiting concentration of a salt Avhich just failed to pro- 

 duce any perceptible change in the sol after an interval of five 

 minutes, was taken to be the measure of its coagulating power. 

 This method is more sensitive than other methods [Mukherjee, J. 

 Amer. Chem. Soc, 37, 2024 (1915)]. The coagulating power of 

 an electrolyte is dependent on the quality of the sol, the sulphide 

 content, its age and the temperature [Mukherjee and Sen. Journ. 

 Chem. Soc, 115, 462 (1919); 117, 350 (1920)]. 



Thé present investigation was carried on with the same sample 

 of sol in order that the data can be strictly comparative. To 

 minimise the effect of " aging ", the sol was allowed to stand for 

 one year before the experiments were made [Compare Pauli and 

 ]Matula, (Koll. Zeitsch, 1, 1917) who took the same precaution 

 with ferric hydroxide sols]. The sol contained 37.6 milimoles of 

 arsenious sulphide per litre. 



One c.c. of the sol was placed in each of ten carefully cleaned 

 test-tubes of Jena Glass. Two c.c. of solution of a salt of different 



Table I. 



x^ r ,, • Limiting concentration 



Cobaltammine .-ß txt i\ 



(Eq. Mol) 



1 [Co (NH3), C,0 J 01 



2 [Co (NH3), (NO,), a|]3 [Co (NO,)e] 



3 [Co(NH3),(N0,),g|]01 



4 [Co(NH3).,(C03)],S0, 



5 [Co (NH3), (NO,), g{] [Co (NH3), (NO,)J 

 G [Co(NH3),(NO,),iJ>]Cl 



7 [Co(NH3),C03]N03^H,0 



Mean 



10 



1500 



9 

 1500 



8 

 1500 



S 

 lôOO 



8 

 1500 



7 



1500 



•7 



1500 



8 

 1500 



