130 
Similar observations were made by Prescorr’) and Lyre’). A long 
time afterwards an investigation was made into the value of the 
molecular-weight of the sodium compound by Noyes and Wrraner ®), 
on the basis of the lowering of freezing-point which would occur in 
dissolving Al in NaOH. As however no perceptible lowering in the 
freezing-point took place and therefore the number of particles before 
and after the dissolution had to be equal, they determined upon the 
composition: NaAlO,; this compound was supposed to be divided 
into two ions and so to form just as many particles as the original 
NaOH molecules. It need not be demonstrated any further that this 
reasoning is uncommonly weak and little suitable as a powerful 
argument in favour of the composition NaAlO,. 
Herz‘) ascribes the composition: Na,AlO, and K,AIO, to the 
Al 
3 
equal to 1 : 1. On the ground of similar experiments Woop ’*) on 
the other hand again arrives at the composition: NaAlO,; although 
from his figures the proportion NaOH: Al,O, often proves much 
larger than would agree with this composition. 
Hantzscn *) performed some conductivity measurements in alumi- 
nate solutions of various concentrations and concludes from these 
that the aluminates behave like salts of mono-basie acids. With such 
salts, which are even hydrolized to a great extent in fairly concen- 
trated solutions forming partly colloidal Al(OH),, the conductivity- 
method entirely loses its value. We are not even sure of the nature 
of the ions present. Hanrzscu’s observations therefore cannot teach 
us anything of the composition of these salts. 
Finally we may still mention that SiapE’) tried to find out the 
composition by applying the law of mass action to aluminate solu- 
tions that are in equilibrium with Al(QH),. His reasoning does not 
hold exactly, because in diluted solutions the solubility of Al(OH), 
is extremely slight, so that small observation errors become of 
very great influence on the final result. In the strong NaOH solutions 
of comparatively large viscosity, in which the solubility can be 
measured very well, it becomes inadmissible to apply the law of 
aluminates, because in solution he found the proportion Na: 
1) Journ. Amer. Chem. Soc. 2, 27. 
2) Chem. News 51, 109 (1885). 
3) Zeitschr. f. phys. Chem. 15, 694 (1894). 
4) Zeitschr. f. anorg. Chem. 25, 155 (1900). 
6) Journ. Chem. Soc. 93, 411 (1908). 
6) Zeitschr. f. anorg. Chem. 30, 296 (1902). 
7) Zeitschr. f. Elektroch. 17, 261 (1910). 
