82 



UV lamp, three test tubes with a frozen rhodamin solution, one 

 containing at the side of the dye 0.1 M NaCl, another 0.1 Af KG. 

 and the third no salt at all. The latter two will show hardly any 

 phosphorescence, while the tube with NaCl shows an intense red 



c 

 o 



I/) 

 I/) 



E 



Nl 0.001 



Fig. 22. Light emission of a frozen aqueous rhodamin B solution (10^^ 

 M) in the presence of various concentrations of NaCl, KCl, Rb, and 

 CsCl. 



The abscissa corresponds to the weak light emission of the control tube 

 with no salt, so the curve's going below it means quenching. 



glow at the temperature of our freezing mixture. It is very impres- 

 sive, indeed, to see the difference of the two so closely related ions 

 demonstrated in such a striking fashion. 



The hydrate shell of Li^ is still bigger than that of Na+ and so 

 the disorder and harm caused by this ion have to be still graver. 

 For the biologist the action of Li" is not less interesting than that 

 of Na", having been discovered by Herbst that it induces mon- 

 strosities in developing embryos exposed at an early stage for a 

 short while to relatively low concentrations of Li+. In rhodamin 

 the graver disorder declares itself in a quenching of light emis- 

 sion. Since the light emission of (salt-free) rhodamin is rather 

 weak this action is not very impressive. For the demonstration of 



