ON ELECTROLYSIS AND ELECTRO-CHEMISTRY. 219 
in a liquid of normal fluidity by multiplying by the coefficient of viscosity 
referred to pure water. The numbers as corrected in the way thus in- 
dicated are given in the fourth column headed C’ (wv being taken at 
‘1 litre). The improvement of the agreement throughout the range of 
numbers is sufficiently apparent. 
The application of Ostwald’s formula is confirmed by observations of 
Van ’t Hoff and Reicher.! 
Arrhenius has further applied the dissociation hypothesis to account 
for the observed results obtained for the conductivity of mixtures, and 
has also recast his theory of chemistry to comply with the more recent 
development of the dissociation theory without interfering with its 
appositeness to the explanation of chemical observations, and he has 
deduced the effect of neutral salts upon the reaction velocities of weak 
bases and acids in saponification, and compared the results with observa- 
tion, and found a satisfactory agreement. 
De Vries, in a paper on osmotic experiments with living membranes,” 
has compared the values of isotonic coefficients * as calculated from the 
molecular conductivities and observed with membranes, and found a 
satisfactory agreement.* 
In an interesting paper ° on the effect of the dissociation theory upon 
the general ideas of chemistry, Ostwald explains the thermal effects of 
reactions in dilute solutions. If, for instance, solutions of KHO and 
HCl are mixed, a quantity of heat, 187K,° is produced, and this heat has 
hitherto been regarded as the heat of formation of KC]. But on the 
dissociation theory the KCl remains dissociated in the solution to the 
extent, at any rate, of 90 per cent. At the same time an equivalent of 
water is formed by the union of the H of the HCl and the HO of the 
KHO;; the heat set free by this may be taken to be 135K, and it consti- 
tutes nearly the whole amount of the heat developed. On this view, for 
all those reactions in which an easily dissociated salt is formed, together 
with a molecule of water, the heat of formation will be that of the mole- 
cule of water merely, and will not depend on the other reacting bodies. 
This is amply borne out by the data supplied by Thomsen for the heat of 
neutralisation of a number of acids by soda solution. When two mole- 
cules of water are formed (with dibasic acids) the heat of neutralisation 
is doubled. The differences are accounted for by the incompleteness of 
the dissociation of the acid and bases, so that the heat of neutralisation 
of an equivalent of acid may in general be represented by a formula 
The theory is also extended to the explanation of the thermo-neutrality 
of solutions—that is, to the absence of heating effect when neutral salts 
are mixed, and the exceptional cases—e.g. the chloride of mercury—are 
those cases in which the dissociation of the salts is not nearly complete. 
It is interesting to note how far the dissociation is supposed to be 
earried. For Arrhenius’s table, an electrolytic molecule may be resolved 
1 ZLeitschr. fiir ph. Chem. 2, p. 777, 1888. 2 Ibid. p. 415, 1888. 
8 Solutions which have equal osmotic pressure are called isotonic, and the corre- 
sponding concentrations isotonic caqncentrations. The reciprocal of the isotonic 
concentration in molecular quantities is called the ‘isotonic coefficient,’ which is 
therefore the number of litres per gramme-molecule required to give a certain 
Osmotic pressure. : 
* L.c. p. 430. 5 Zeitschr. fiir ph. Chem. 3, p. 588, 1889. 
® K represents 100 gramme Centigrade thermal units. 
