Permeability 11 
nitrates of sodium, lithium, zinc, manganese and magnesium, the 
sulphates of the last three named metals, and the acetates of zinc 
and manganese all gave negative osmosis. Confirmatory results 
were obtained by using pure water in the cell and solutions 
outside. 
It is important to observe that the membranes employed are not 
semi-permeable, and indeed the incidence of negative osmosis is 
related to the diameter of the pores in the membrane. Thus with 
M/ io magnesium chloride solutions, and with porcelain membranes, 
no apparent osmotic effects were produced when the diameter of the 
pores was greater than 0-4/x, with pore diameters between 0-4,11 and 
o-i )jl negative osmosis was observed, while with pore diameters less 
than o-i/x osmosis was in the positive direction as with semi-per¬ 
meable membranes. 
Further observations were made by Bartell and Hocker (1916 b) 
on the osmosis of the following solutions: (1) nitrates of a number 
of univalent (K, NH 4 , Na, Li), bivalent (Ba, Zn, Mn, Mg), trivalent 
(Al) and tetravalent (Th) kations in concentrations varying from 
0-0005 M to M ; (2) o-i M solutions of a number of potassium salts 
(N 0 3 , Cl, Br, I, CNS, acetate, S 0 4 , Cr 0 4 , P 0 4 , ferrocyanide and 
ferricyanide); (3) hydrochloric acid and sodium hydroxide in con¬ 
centrations from o-ooi M to 0-2 M, and (4) o-i M solutions of some 
nitrates when the membranes were immersed in solutions of acids 
and alkalies in different concentrations. 
The results obtained were very varied. In some cases positive 
osmosis occurred in all concentrations, increasing regularly with 
increase in concentration, in others positive osmosis occurred in low 
concentrations but decreased with increasing concentration so that 
in higher concentrations negative osmosis occurred. In other cases 
there was observed a definite concentration for maximum positive 
osmosis which decreases with either higher or lower concentrations, 
while with yet other electrolytes there is a concentration for maxi¬ 
mum negative (or minimum positive) osmosis, all concentrations 
above or below this value giving more positive effects. 
More recently Bartell and Madison (1920 a) have shown that 
abnormal osmosis also occurs with membranes of gold-beaters’ skin, 
the flow of water across the membrane being sometimes in the direc¬ 
tion of solvent to solution, sometimes in the reverse direction. In 
the case of normal (positive) osmosis, the flow, as compared with 
that into a solution of sucrose, was sometimes abnormally large and 
sometimes abnormally small. The same authors further show (1920 b) 
