POTASSIUM AND RUBIDIUM SALTS. 31 



CAN POTASSIUM SALTS BE REPLACED BY RUBIDIUM SALTS IN GREEN 



PLANTS AND IN ANIMALS? 



Various authors have shown that potassium can not be replaced in 

 plants by sodium or by lithium, starvation phenomena occurring with 

 the former and toxic phenomena developing with the latter (Nobbe). 

 As regards their atomic weight, sodium and lithium stand below while 

 rubidium and caesium stand above potassium, as follows: 



Li = 7 



Na = 23 ' dilL : 16 



K = 39 diff,: 16 



Rb = 85.4 diff.: 16x3-1.6 



Cs = 133 diff.: 16X3-U.L 



Since the properties of elements are to a certain extent functions of 

 their atomic weight, it might be supposed that the physiological capa- 

 bilities of the alkali metals would increase with their atomic weight, 

 but the facts observed are not in accord with this view. 



Molisch has demonstrated that alga? can not develop if the potas- 

 sium salts of the culture solution are replaced b} T rubidium salts." In 

 animals, also, neither caesium nor rubidium salts can take the place of 

 potassium salts, although a moderate amount of the rubidium salts is 

 not noxious, and in large quantities they are even less injurious than 

 the potassium salts. 6 



Birner and Lukanus*' demonstrated that plants soon perish when the 

 culture solutions contain rubidium or caesium nitrate in place of potas- 

 sium nitrate. In experiments with buckwheat plants the writer after- 

 wards confirmed this conclusion as regards rubidium nitrate,"' not taking 

 caesium salts into consideration; but he observed in addition that the 

 action of rubidium chlorid differed to some extent from that caused 

 by rubidium nitrate. Where the chlorid was offered the plants 

 attained a greater height than with the nitrate. Those with rubidium 

 nitrate died before the flowers were formed, while those with rubidium 

 chlorid died after that period. Torsion and thickening of the stalk 

 and curling and rolling up of the leaves were the most striking results 

 with rubidium nitrate. In both cases, however, a diagnosis of the 

 pathologic characters revealed essentially a disturbance in the functions 

 of the chlorophyll bodies and in the transportation of starch, the effect 

 on the latter being more marked with the nitrate than with the chlorid. 

 A chemical comparison of buckwheat plants grown with potassium 

 chlorid and of those grown with rubidium chlorid showed (1) that the 



«On the other hand no injurious influence upon algae is noticed when to the com- 

 plete culture solutions 0.3 per mille of the chlorids of rubidium or caesium is added. 



''According to Richet, the lethal minimum dose of rubidium in form of rubidium 

 chlorid is 1 gram for 1 kilo body weight when applied subcutaneously. This is about 

 twice as much as the lethal dose of potassium chlorid. 



'Landw. Vers. Stat., Vol. VII, p. 363. 



tf.Landw. Vers. Stat., Vol. XXI, p. 389. 



