If properties at first unwelcome have at last been turned to account, so also have properties which were long deemed utterly useless. A big and interesting book might be filled with the story of how by-products, long thrown away as worthless, have rewarded careful study with great profit. Thus for ages was bran discarded in flour-mills: to-day it may afford all the miller’s profit, or even more than that profit. In the Southern States until a generation ago cotton seed was regarded as valueless. At present that product, so long wasted, is the basis of a great industry, a ton of seed yielding about 1089 lbs. of meat to 20 lbs. of lint; out of this meat 800 lbs. are cake and meal; the remainder, 289 lbs., forms an oil which furnishes a substitute for olive oil and lard. Until a few years ago glycerine was thrown away as produced in candle-works and soap factories. It is now so valuable that manufacturers adopt just that method of preparing fatty acids which yields most glycerine from neutral fats. So in paper-making, the soda which formerly was sent into creeks and rivers to the pollution of sources of water-supply, is now used over and over again, largely increasing the net results of manufacture. No industry has shown of late years so large utilization of products formerly wasted as the iron and steel manufacture. Its slags are made into bricks, cement, and glassy non-conductors of heat and electricity. Its gases are used for engines developing immense motive powers, or they are in part condensed for valuable acids or other compounds. In these cases and thousands more the question has been, What are the properties of these by-products? How can they be made useful?
Separation Turns on Diversity of Properties.
Let us note how diverse substances are separated from one another by taking hold of differences in their properties. When a handful of grain which has just passed under a flail is thrown upward in a breeze, its chaff is blown much farther than the grain; the difference in breadth of surface, joined to a difference in density, enables the wind to effect a thorough separation. A common fanning mill, with its quick air current, works much better than the fitful wind, because continuously. That simple machine, like every other which takes a mixture and separates its ingredients, seizes upon a difference in properties. In Edison’s apparatus for removing iron from sand or dust, a series of powerful magnets overhang a stream of sand or powdered material, deflecting the iron particles so that they fall into a bin by themselves, while the trash goes into an adjoining larger bin. The Hungarian process of flour-milling first crushes wheat through rollers; the various products are then separated by processes which lay hold of differences in specific gravity—often but slight.
A feat more difficult than that of the Hungarian mill would seem to be the division of diamonds from other stones. It has been accomplished by Mr. Frederick Kersten of Kimberley, South Africa. He noticed one day at his elbow a rough diamond and a garnet on a board. He raised one end of this board, and while the garnet slipped off, the diamond remained undisturbed. What was the reason? He observed that the wood bore a coating of grease, which possibly had held the diamond while the garnet had slipped away. He took a wider board, greased it, and dropped upon it a handful of small stones, some of which were rough diamonds. He found that by inclining the board a little, and vibrating it carefully, all the stones but the diamonds fell off, while the diamonds stuck to the grease. He forthwith built a machine with a greasy board as its separator, and scored a success.
On quite a different plan is built the coal washer which separates coal from slate. Pulses of water are sent upward through a sieve so as to strike a broken mixture of coal and slate, making a quicksand of the mass. Because the slate is heavier than the coal it is not carried so far, and is therefore caught in a separate stream and thrown away.
Properties Newly Discovered and Produced.
Separations, such as we just considered, turn upon obvious differences in density. Properties not obvious, yet highly useful, come into view year by year as observers grow more alert and keen, as new instruments are devised for their aid, as measurements become more refined, so that matter is constantly found to be vastly richer in properties than was formerly supposed. We have long known that carbon has forms which vary as widely as coal, graphite and the diamond. Many other elements are detected in a similar masquerade. Iron, for instance, takes three forms, alpha, beta, and gamma. Alpha iron is soft, weak, ductile and strongly magnetic; beta iron is hard, brittle and feebly magnetic; gamma iron is also hard and feebly magnetic, yet ductile. Joule, the famous English experimenter, prepared an amalgam of iron with mercury; when he distilled away the mercury, the remaining iron took fire on exposure to the air, proving itself to be different from ordinary iron. Moissan has shown that similar effects follow when chromium, manganese, cobalt and nickel are released from amalgamation with mercury.
At first steel was valued for its strength and elasticity; to-day we also inquire as to its conductivity for heat or electricity, its behavior in powerful magnetic fields, its capacity to absorb or reflect rays luminous or other. As art moves onward we enter upon new powers to change the properties of matter, compassing new intensities of heat and cold, each with new effects upon tenacity, elasticity, conductivity. So also with the extreme pressures, possible only with modern hydraulic apparatus, which prove marble to be plastic, and reduce wood to a density comparable with that of coal, explaining how anthracite has been consolidated from the vegetation of long ago.
And one discovery but breaks the path for another, and so on indefinitely. Coming upon a new property, the sensitiveness of silver compounds to light, meant a new means of further discovery, the photographic plate. That plate, responsive to rays which fall without response upon the retina, reveals much to us otherwise unknown and unsuspected. Of old when an observer saw nothing, he thought there was nothing to see. We know better now. Thanks to the sensitive plate we have reason to believe that properties, once deemed exceptional, are really universal. Phosphorescence, for ages familiar in the firefly, in decaying logs and fish, now declares itself excitable in all substances whatever, although usually in but slight measure. The case is typical: the polariscope, the spectroscope, the fluoroscope, the magnetometer, the electroscope, each employing as its core a substance of extraordinary susceptibility, detects that quality in everything brought within its play. Thus from day to day matter is disclosed in new wealths of properties, and therefore in new and corresponding complexities of structure. In ages past mankind was on nodding terms with many things, and had no intimate knowledge of anything.
With materials before him richer in array than ever before, and better understood than of old, the inventor asks, What properties do I wish in a particular substance? Then, he proceeds to make, if he can, a dye of unfading permanence, an insulator resistant to high temperatures, an alloy which when subjected to heat or cold remains unaltered in dimensions. He finds materials much more under command than a century ago could have been imagined, as the glass manufacture, the alloying industry, the making of artificial dyes, abundantly prove.