The rapid hardening under water of the cement which from that property
derives its name of “Hydraulic Cement,” has been, and indeed is still,
a subject of discussion as to the true theory of such action. We find
in the June number of the _Chemical News_ a paragraph which must prove
very interesting to manufacturers as well as to all who use and take
an interest in that most useful of building materials to which the
Architect and the Engineer are so deeply indebted.
“In order to test the truth of the different hypotheses made
concerning this subject, A. Schulatschenko, seeing the impossibility
of separating, from a mixture of silicates, each special combination
thereof, repeated Fuch’s experiment, by separating the silica from 100
parts of pure soluble silicate of potassa, and, after mixing it with
fifty parts of lime, and placing the mass under water, when it hardened
rapidly. A similar mixture was submitted to a very high temperature,
and in this case, also, a cement was made. As a third experiment, a
similar mixture was heated till it was fused; after having been cooled
and pulverized, the fused mass did not harden any more under water.
Hence it follows that hardening does take place in cement made by the
wet as well as dry process, and that the so-called over-burned cement
is inactive, in consequence of its particles having suffered a physical
change.”
[Illustration: IRON STORE-FRONTS, No. V.