^L^S :^rR. B. D. STEELE OX THE !\rEASUREHEXT OF IONIC VELOCITIES 
scale divisions. Fig. 4 shows, also diagramraatioally, the arrangement of the whole , 
apparatus for an experiment. B represents the hattery. W is the water-bath, 
in which is immersed the apparatus, of Avhich A and K are the anode and cathode 
cells respectively. Pt is a very large and easily varied resistance placed in circuit, 
l 3 y means of Avhich the voltage between A and K can be varied as required. 
Experimental Besults. 
Tlie independence of the margin velocity on the nature of the indicator, provided 
the latter fulfils the required conditions shown by Masson, has been confirmed 
by the measurement of magnesium sulphate with three pairs of indicators—copj^er 
sulphate and potassium chromate, cadmium sulphate and sodium acetate, copper 
sulphate and sodium acetate—and l^y the fact that practically the same result has 
l)een obtained for the velocity of the hydrogen ion Avhen measured Avith sih-er 
nitrate or Avith potassium chloride as cation indicator. 
The iiegatiA^e case has l)een proAmd by a large number of experiments, all of Avhich 
shoAV that, Avhen the faster ion folloAvs the sloAA^er, in cases AA'here a boundary is 
produced at all, the ratio of its velocity to that of the lAOundary at the opposite end 
of the solution is quite inconstant. 
Talde III. contains the results obtained during the research. 
In column I are given the formulse of the salts measured. In the second column 
is p'iven tlie concentration of each salt. 
o 
In column 3, under is giA^en the ratio of the velocity of the anion to that of the 
cation, this l)eing calculated directly from tlie ohserAntion in the manner previously 
described. 
V 
In columns 4, 5, and 6, under giA^en for comparison the Amines of the 
anion transport number. Under S are given the'’numbers obtained by the author, 
under (Masson) those obtained liy Masson by direct measurement in gelatine, and 
under (Hittoee, &c.) are given those obtained by dilferent iiiAmstigators liy the 
Indirect method of Hittoee. The latter numbers are taken from Kohlrausch and 
ITolboen (‘ LeitAmrmogen der Electrolyte’). 
A comparison of tlie figures in the fourth and fifth columns shoAvs that for 
potassium and sodium chloride there is a A^ery close agreement betAveen the 
numliers obtained liy direct measurements in AAmter and in gelatine, Avhilst for lithium 
chloride and magnesium sulphate no such agreement exists. For 2N magnesium 
sulphate there is given in brackets (column 5) the number 0’G88, obtained by the 
author for the value of in gelatine; this measurement being made for purposes 
of comparison. For this salt the gelatine results agree among themseb’es, as also 
do the aqueous; Avhereas the tAvo sets of measurements sIioav no such agreement as 
