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lead a current of CO, into the aluminate solution, the precipitate 
is perceptibly more floecose and the particles are coarser than if 
we cause if to arise by a prolonged exposure to the air. 
Product y. A very remarkable and, so far as I know. in the 
literature not yet described form of the hydroxide, arose as follows: 
The dessiccated particles of product «, which have quite the outward 
aspect of a shrivelled up gellous mass, do not swell in pure water, 
in concentrated NaOH-solutions they swell very rapidly. On being 
shaken a long time with diluted NaOH-solutions, they not only 
were found to give nos welling, but even to pass into « fine crystallized 
product. This transition succeeds best if the concentration of the 
lye is between 0,5 and 2,0 normal, while they are continually 
shaken vigorously. It usually took a few months before the tran- 
sition had taken place completely. It can best be watched micros- 
copically; the original aspect: gelatinous, very irregularly formed 
particles of varions sizes, disappears in the long run and in their 
place we observe: bar-shaped crystals very regular in shape and 
size. No doubt we bere have a crystallized phase: at a 600 fold 
magnification the crystals could be distinctly observed. Their length 
amounted to 8—20 wu, their width + 3 u, they are faintly double- 
refractive. 
The remarkable phenomenon is especially that we have here a 
direct transition from the gelatinous state into the crystalline state, 
of which no examples have been stated with any certainty as yet. 
Where we see that, dependent on the OH’-ions concentration, the 
gelatinous mass of aluminiumhydroxide crystallizes or swells to 
amorphous particles, this pleads very strongly in favour of the 
gradual transition of the crystallized and the amorphous state of 
matter. This has been suspected on the ground of various phenomena, 
but the direct experimental proof is still wanting. The systematical 
study of the crystallization and swelling of such bodies as aluminium- 
hydroxide may probably improve our insight into this transition 
Anyhow the swelling of aluminiumhydroxide as a function of the 
H: and OH’-ions concentration is remarkable and a further study 
about this is in progress. 
On using the product y, close attention should always be paid 
that it no longer contains any gelatinous particles of product a, 
as these possess a greater solubility in lyes, so that in this case we 
should not measure the exact solubility of 7. A microscopical control 
of the form y was therefore applied with all following determinations. 
Analysis of the product yielded: 34,35 °/, H,O - 65,52 °/, Al,O,, 
so corresponding with Al,O,.3H,O (after drying at 100—110)). 
