564 Butter.—Contributions to our Knowledge of the 
In Tables I and II it will be noticed that,, whereas potassium 
nitrate attracts, the nitrates of sodium, lithium, ammonium 
and calcium do not, and that while potassium chloride attracts 
this is not the case with the chlorides of sodium, ammonium 
and calcium. 
The solutions of these salts are ionized, the ions being 
in each case the negative radicle and the metal. The amount 
of ionization is considerable. At a concentration isomolecular 
with yV mol potassium nitrate 1 , it is 70-86 °/ o of the mole¬ 
cules in solution, while at lower concentrations it is of course 
still higher. From the fact that the solutions of sodium, 
ammonium, lithium and calcium nitrates and also sodium, 
ammonium and calcium chlorides do not attract it would 
seem justifiable to conclude that neither the ions Na + , NH t> 
Li + , Ca+, Cl - , NO3 nor the whole molecules NaCl, NH 4 C 1 , 
CaCl 2 > NaNCb, NH4NO33 LiN 0 3 , Ca(N 0 3 ) 2 give a positive 
chemotactic stimulus. 
Potassium nitrate and potassium chloride both attract. 
If, however, the ions Cl - and NO<T do not attract it is evident 
that the attraction of these salts is due to the ion K + or 
possibly to the whole molecules KN 0 3 and KC 1 or to the 
combined effect of the K + ions and the respective whole mole¬ 
cules. At a concentration of -^o mol, potassium nitrate is 
ionized to the extent of approx. 81 °/ o and potassium chloride 
to 86°/ o . Owing to this high dissociation and also to the 
known chemical activity of the ions in a solution it seems to 
me that we may neglect the second possibility and assume 
that it is highly probable that the ion K + gives a positive 
chemotactic stimulus. 
If K + ions attract, it is reasonable to suppose that any 
other neutral salt of potassium in which the ion K + is present 
also attracts. So far as my experiments have gone with nine 
other potassium salts this supposition has been justified. 
Thus attraction is given by solutions of potassium iodide, 
bromide, sulphate, chlorate, phosphate (K 2 HP 0 4 ), tartrate, 
acetate, oxalate and sodium potassium tartrate. 
1 Calculated from the tables in ‘Solution and Electrolysis.’ Whetham, 1895. 
