If, however, the experimental difficulty has not
been overcome in an entirely satisfactory manner, it at least appears
very probable that such walls may nevertheless exist.[16]
[Footnote 15: See next note.--ED.]
[Footnote 16: M. Stephane Leduc, Professor of Biology of Nantes, has
made many experiments in this connection, and the artificial cells
exhibited by him to the Association francaise pour l'avancement des
Sciences, at their meeting at Grenoble in 1904 and reproduced in their
"Actes," are particularly noteworthy.--ED.]
Nevertheless, in the case of gases, there exists an excellent example
of a semi-permeable wall, and a partition of platinum brought to a
higher than red heat is, as shown by M. Villard in some ingenious
experiments, completely impermeable to air, and very permeable, on the
contrary, to hydrogen. It can also be experimentally demonstrated that
on taking two recipients separated by such a partition, and both
containing nitrogen mixed with varying proportions of hydrogen, the
last-named gas will pass through the partition in such a way that the
concentration--that is to say, the mass of gas per unit of volume--
will become the same on both sides.
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