Philip Quilibet.
SCIENTIFIC MISCELLANY.
THE FORCE OF CRYSTALLIZATION.
The old story of a bombshell filled with water and left to burst by freezing, upon the plains of Abraham, near Quebec, may now be superseded as an illustration of the power of frost. The men at a Western dockyard were surprised to find one morning that the paddle-wheel of a steamer in the dry dock had fallen from the shaft, and was broken in two pieces. The hub of the wheel, about fifteen inches long, was slightly hollowed out at the centre to admit of its being slipped on without difficulty over any uneven portion of the shaft-end. This recess was full of water when the boat was placed in the dock, and the keying had been so close that the liquid—about a pailful—was exposed to the frost. As the water congealed under the sharp wintry atmosphere of the night it expanded and burst asunder the five-inch walls of iron, and the broken wheel fell with a crash.
FROZEN NITRO-GLYCERINE.
Two accidents, both fatal, have lately occurred from the use of nitro-glycerine for blasting. In one case some frozen cartridges were recklessly placed in the oven of a stove, while others were held up to the fire. That an explosion should take place under such circumstances is not surprising, and comment is unnecessary. The other explosion partook more clearly of the nature of an accident. A well digger, living near Sing Sing, had buried a can of nitro-glycerine in his garden for future use; and while digging it up, January 18, his pick struck the can, ignition followed, and he was blown to pieces. No doubt the can was frozen, thus proving anew that frozen nitro-glycerine is more dangerous to handle, though not so powerful in its effects, as in the liquid form. This is singular behavior and contrary to theory. In general terms, explosion may be defined as the result which takes place when a portion of the nitro-glycerine is raised to a given temperature. Now, to produce this temperature by the friction resulting from the blow of a pick is manifestly more difficult with frozen than with tepid liquid. In the former case some of the heat produced would be absorbed by the liquefaction of the solid substance, and therefore there would be less available for producing the temperature of explosion. But, plain as this proposition is, there must be some unknown condition, for it has been frequently observed in practical work that nitro-glycerine is never so dangerous to handle as when frozen. This result, however, is directly opposed to the experiments of Beckerhinn, of Vienna, who lately experimented to decide this question. He placed a thin layer of nitro-glycerine on a Bessemer steel anvil, and a weight of about five pounds, having a small hardened steel face, was dropped upon it. The height to which it was necessary to raise this weight in order to produce explosion determined the comparative delicacy of the explosive. With tepid nitro-glycerine explosion took place when the weight dropped about 31 inches (0.78 metres), but with frozen liquid the fall had to be increased to about 85 inches (2.13 metre). Thus the experimental results are opposed to the acknowledged experience of practical work in the hands of common laborers. Mr. Beckerhinn found the density of the solid nitro-glycerine to be 1.735, that of the liquid 1.599, and the average melting heat to be 33.54 heat units. Thus the explosive shrinks about one-twelfth in crystallizing.