134 
B. Aluminiumowide. 
The three products of Al,O, that received consideration had 
respectively been obtained by careful, not too long heating at 300°—400° 
of the products a, 8 and y. Long heating was avoided, because this 
makes the oxide very indifferent, so that it delays the reaching of 
equilibrium, nay, may even render it impossible. Taken in the 
same order, in the following these produets will be indicated as 
On esand)5 
Product d, which had been obtained out of «, still made quite 
the impression of a shrivelled up, gelatinous mass; in NaOH-solutions 
the particles again proved capable of swelling or crystallizing dependent 
on the concentration. 
The particles of product € microscopically displayed entirely the 
same aspect as those of 98. The crystals of y proved to alter on 
heating; the oxide § was not distinctly crystalline. 
The equilibriums of aluminiumhydroxide with NaOH-solutions 
of various concentrations. 
The determination of these equilibriums yielded very great diffi- 
culties. The cause of this is partly the occurrence of the hydroxide 
in various forms, partly also the viscosity of the solutions on great 
NaOH concentration. Owing to this, we are in the first place com- 
pelled with each determination to carefully state what solid phase 
is present in the state of equilibrium, which is very often impossible 
by adirect way. In many cases the rest method is applied. Further 
we should continually control whether the values found really hold 
good for the state of equilibrium, in other words whether this state 
has perfectly arisen. This takes a long time, especially in the more 
concentrated solutions; many determinations could only yield repro- 
ducible figures after having been shaken in the thermostat for 2 or 
3 months. The depositing of the solid phases also requiring much 
time, this is the reason that the whole investigation takes up a 
very long time. 
A survey of the determinations performed is to be found in fig. 1 
and table I. The curves J, I] and III in fig. | refer to determinations 
performed with the products «a, 8 and y respectively. In fig. IT 
(page 140) they are indicated by CF, BE and AD. In the third 
column are indicated the solid phases which, when the experiments 
are performed, were added to the NaOH-solutions; in the tenth 
column those which proved present after reaching the equilibrium. 
As will be proved, some equilibriums must be considered metastable, 
