MOLECULAR SPEED R. E. ROSE,E. I. DU PONT DE NEMOURS & CO.. INC.,WILMINGTON, DELAWARE Air is a mixture of molecules. These are moving very fast. On a frosty day their average speed is about one-quarter mile each second or 900 miles an hour. When they move 935 miles an hour you feel comfortably warm, when they race 951 miles an hour you feel disagreeably hot. These are the little things that make or unmake our happiness.
P h o a . ~by S i i r w Srmirr, rrprodurad by courlesy of I n d . En& Chcm.. Nrwr milion
THEMUNROEEFFECT ISA DEMONSTRATION OP HIGAMOLECULAR SPEED One of the most impressive demonstrations of high molecular speed is the phenomenon known as the Munroe effect, whereby tracings of leaves, lace, and other delicate patterns can he reproduced upon the hardest steel by the firing of charges of high explosives. A t left, Charles E. Munroe, explosives expert, U. S. Bureau of Mines, examining piece of chrome steel with portrait reproduced by Munroe effect. A t right, Munroe effectproduced by firing high nitro-gelatin explosive over piece of chrome steel, with photograph in between. Portrait reproduced is of Charles E. Munroe, discoverer of the effect. You do not feel the air molecules strike you but you feel the effect they have on the activity of the molecules of your body. On a very moist hot day you are particularly unhappy because you cannot lose the lively water molecules from your s k i , leaving the cooler ones behind. It is amazing what a speeding up of molecular motion will accomplish. A stick of dynamite, that most useful of modern conveniences, is nothing
VOL. 5, No. 11
MOLEC~LAE SPEED
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more than a package of molecules that can be caused to turn into others moving with a velocity that amounts to three-quarters of a mile per second. The molecules in the dynamite are built like a top-heavy house with weak members. The nitroglycerine and the ammonium nitrate are just in this condition, give them a knock and over they go, only the knock has to be of a particular kind to make sure of results. But the fragments of molecules are new molecules and these do not settle like the dust from a falling house, they fly in all directions, spurred on by the energy which was tied up in the explosive materials. The farmer, blowing up a stump, takes a fuse which contains fulminate of mercury, a frightfully sensitive kind of molecule. He fits this on a fuse, crimps i t tight, takes a stick of dynamite and makes a hole in it into which he shoves the cap, then, the fuse being fastened, he puts the dynamite in a hole under the stump, puts more sticks of dynamite in, then rams them home, and covers them with earth. Then he starts the molecules moving. Those on a match head get lively enough when excited by the heat of friction on his pants, the match stick starts burning, the molecules of the flame upset the molecules in the fuse. Then the farmer runs to shelter and the next moment the spurt of fiery molecules from the fuse hits those of the fulminate in the cap. Away they go smashing the metal cap to pieces and hitting the dynamite a knock-out blow, the whole mass topples to pieces and the pieces push against the earth and against the stump-up goes the stump, lifted by particles of which forty million edge to edge would measure only one inch. The control of molecular speed is the underlying fact upon which our civilization is built.
