APRIL 7, 1904] 
NATURE 
545 
It is true that with the establishment of a mining course 
in Johannesburg the engineering establishment at the South 
African College is faced to a certain extent by competition, 
but there is no reason why the earlier stages of instruction 
should not be taken at the South African College and the 
final stages at Johannesburg, where special facilities will 
exist. As to the future contingency of overlapping, Prof. 
Hele-Shaw suggests, in the probable event of an engineer- 
ing faculty being established, that while the Transvaal 
could devote itself solely to mining engineering, the Cape 
University could develop the study of naval, architectural 
and marine engineering, for which there would be special 
facilities in the peninsula. 
In his remarks on the future relations of the University 
of the Cape of Good Hope and the Transvaal Institute, Prof. 
Hele-Shaw said the present year will see the work of a pro- 
fessorship of engineering commence at both places, and 
continued, ‘‘ There need be no fear of overlapping, since 
such a course, though suitable, and, indeed, necessary, for 
any branch of the constructive professions, can in the later 
stages be specialised to suit the local requirements. ‘Thus 
in the north mining would naturally be a strong feature of 
a special course, whilst your city (Cape Town) has possi- 
bilities in the way of naval architecture and marine 
engineering which even the wildest dreams of the projector 
of the ship canal to Johannesburg would never contemplate 
for the latter city. Such a faculty of engineering, if true 
to its proper aims, would, by right, take its place, as re- 
presenting a learned profession amongst the other great 
faculties, and would doubtless have its distinctive university 
degrees.”’ 
Speaking more particularly of the new institution at 
Johannesburg, Prof. Hele-Shaw said :—‘‘ The university 
idea will, I trust, even at its initial stages, be fully main- 
tained in the Transvaal Institute, not by any mere artificial 
standards of entrance, but by the due appreciation of the 
spirit in which learning should be sought and teaching 
given. There will be due provision made that all entering 
students shall by their previous training be able to take full 
advantage of the lectures and classes, just as provision is 
made for this at the South African College. But the doors 
of the institute will be closed to no one, however humble, 
who seeks such knowledge and is able to take advantage 
of it. This freedom for the acquisition of learning is a very 
different thing from the granting of diplomas to those who 
are unworthy. In its diplomas and certificates the insti- 
tute will try to follow the highest standards, and in this we 
can hope for your friendly cooperation and support. For 
the present our mining students will derive incalculable 
benefit from the seal and stamp which you will set upon 
their university career, a seal which will derive its value 
from the high standard which you have ever striven to 
maintain amongst your graduates. You may be sure that 
whatever developments there may be in the future when our 
own university becomes an accomplished fact, the same safe- 
guards for a university degree will be enforced for our 
university as there are for yours. No university degree can 
have any value which does not insist upon evidence of some 
amount of literary knowledge and include an acquaint- 
ance with more than one language on the part of its 
graduates—in a word, upon evidence of liberal education.” 
Referring to the fears expressed in some quarters in con- 
nection with a possible over-multiplication of universities, 
Prof. Hele-Shaw remarked :—‘ There is abundant evidence 
that the proportion of the population who are imbued with 
a love for higher learning and a determination to secure 
a university standard is far greater here than in the cities 
of the older countries. There may, possibly, exist some fear 
of what I have called a multiplication of universities—a fear 
that one university may arise and grow at the expense of 
another. I have heard this fear expressed in the instances 
with which I myself am personally acquainted ; but I have 
also seen this fear prove groundless. In the first place, it 
is known that the university which lowers its standard in 
the hope of attracting students thereby inevitably compasses 
its own downfall, and in the second place the remarkable 
effect of the institution of a new university seems to be that, 
whilst educational enthusiasm has been aroused in a new 
centre, a patriotic and zealous spirit has been rekindled in 
the old, and both universities have flourished where before 
one was only languishing.” 
NO. 1797, VOL. 69] 
THEORY OF AMPHOTERIC ELECTROLYTES.* 
MPHOTERIC electrolytes are those which are capable 
- of acting as acids towards bases and as bases towards 
acids. One of the simplest types is that of the amino-acids, 
for example, glycine, NH,.CH,.COOH, which in virtue of 
the NH, group is an anhydrous base, whilst in virtue of the 
COOH group it is an ordinary organic acid. When such 
a substance is dissolved in water, it is ionised as acid, as 
base, and as the salt formed by their reciprocal neutralisa- 
tion. From molecular weight determinations in aqueous 
solution it is found that in general the molecule is simple 
and not double, so that the unionised salt must be 
NH,.CH,.COO 
The theory of the ionisation and electrical conductivity 
of the aqueous solutions of amphoteric substances may be 
deduced by a consistent application of the law of mass 
action and Arrhenius’s theory of electrolytic dissociation. 
If the anhydrous electrolyte is represented by the formula X, 
and the hydrated form by the formula HXOH, the ions 
found in the solution will be 
H+ OH— XOH— HX+ 
a b c ad 
The letters beneath the formule represent the active 
masses for equilibrium of the corresponding ions. With 
regard to the active masses of the various forms of unionised 
electrolyte, it can easily be shown that these are in fixed 
ratios, whatever the concentration may be. We may there- 
fore represent the sum of the active masses of the unionised 
forms by the letter u, and by considering the equilibrium of 
the different pairs of positive and negative ions, arrive at 
the following expressions :— 
x K+ katt 
a= = 
1 +f x 
6=K/a 
6=hgua 
d=k,ua/K, 
in which K represents the ionic product for water, hk, the 
dissociation constant of the amphoteric electrolyte acting as 
acid, and k, the dissociation constant of the amphoteric 
electrolyte acting as base. The value of K is well known, 
and #, and & may be obtained from measurements of the 
degree of hydrolytic dissociation of salts of the amphoteric 
electrolyte. For feebly ionised electrolytes u is very nearly 
equal to the total active mass, and may be assumed to be 
so in the first approximation. It is therefore possible to 
calculate the concentrations of the various ions from a know- 
ledge of the constants given above and of the total concen- 
tration. From these ionic concentrations and the corre- 
sponding ionic velocities the electrical conductivity of the 
solution may then be calculated. 
This calculation has been made from Winkelblech’s data 
for the amino-benzoic acids, and satisfactory agreement 
obtained with the observed numbers. For such substances 
the dissociation constants calculated from the conductivity 
by Ostwald’s formula have been always found to be 
abnormal. The theory given above explains the abnormality, 
and accounts numerically for the variation in the ‘‘ con- 
Stantewae 
In general it may be said that in the case of amphoteric 
acids which have a ratio k,/K of the order 100 to 1000, the 
Ostwald constant k, is greater than the true acid constant 
ka at high concentrations, falls to a minimum considerably 
lower than k,, finally to rise asymptotically to the true value 
k, as dilution progresses. The conductivity at the high 
concentrations is chiefly due to the ionisation of the electro- 
lyte as salt, whereas at the high dilutions it is mostly due 
to the ionisation of the electrolyte as acid. In consequence 
of this, the measurement of the conductivity. of solutions of 
amphoteric electrolytes affords no criterion of their strength 
as acids. An amphoteric electrolyte in which the acidic 
and basic constants are equal would give solutions abso- 
lutely neutral at all concentrations, and possessing a mole- 
cular conductivity invariable with the dilution, thus differing 
from all simple acids, bases or salts. 
1 Substance of a paper by Prof. James Walker, F.R.S. Read before the 
Royal Society on February 18. 
