ELECTROLYTIC DISSOCIATION. 



393 



ZV 



A± 



K>~r\ 



J\- 



Fiuoresceine H, 

 Potassium sail H, Ho 

 DichlorfN* CI, H, 

 Telrabromf H, Br, He 

 Telrajodf U «« 



sail K, I, H f 

 OaelhtjItetrajodftCtH^ r. « c 

 TelrabromdichlorfK, Br, CI, «« 

 TelrajoddichlorC K, J, CI, H, 

 TtlrabromdunilrohjIhQ,^ Qr, H t 



silver and chlorine compounds as are in a measurable degree decom- 

 posed into silver and chlorine ions. Ostwald has treated this question 

 comprehensively, and in this way 

 he has given a rational exposition 

 of the general phenomena of an- 

 alytical chemistry. To this fact 

 belong, also, the poisonous effect 

 of some salts; this effect may be 

 considered as a special physiolog- 

 ically chemical reaction of the 

 chemical compounds. On this 

 point there are many valuable 

 researches by Kronig and Paul, 

 Clarke and others. 



A property that is of physical character, but is much used by the 

 analytical chemist, is the color of the solutions. It has been subjected 

 to a rigorous research by Ostwald. At first we will trace how a com- 

 pound, e. g., fiuoresceine, H 12 C 20 O 5 , behaves if one replaces its hydrogen 

 atoms by other atoms, e. g., metals, iodine, bromine or atomic groups 

 (N0 2 ). The curves in the next figure (Fig. 7) indicate absorption- 

 bands in the spectra of the corresponding compounds. A replacement 

 of K 2 for H 2 in the fiuoresceine itself alters the absorption-spectrum 

 in a most sensible manner. This depends upon the property that the 

 fiuoresceine is dissociated to a slight extent, which is in striking con- 



Derwatts of Fiuoresceine, S,t C20 Os 

 Fig. 7. 



Perm ana cuiatcs 



Fig. 8. 



Salte or PararosaniluLe, 



Fig. 9. 



Buturate 

 Sulphate 



trast to the permanganic acid which will be discussed immediately. 

 Instead of a single absorption-band in the blue in the first case, we find 

 two absorption-bands in the blue-green and the green part of the spec- 



