Page:Popular Science Monthly Volume 23.djvu/825

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excellent material for making the commoner grades of paper, suitable for wrapping and newspaper purposes.

The present sources of the supply of potash are rapidly failing; every year the area of the supply becomes smaller, and the product, in consequence of this and the increased demand, becomes more and more expensive. The cobs of Indian corn, which are now considered of little or no value, may yet share the same fate as many substances which, though formerly considered worthless, have become new mines of wealth, through the aid of chemistry.

The average yield of 1,000 parts of cobs is 7·62 parts of carbonate of potash, or nearly twice as much as the best specimens of wood, and it is a material which can fill its full measure of usefulness for other purposes, before it comes into the hands of the manufacturer of potash. At the shipping ports, large shelling-mills are established, capable of running through 500 bushels of corn an hour. Here, then, are the places where a supply of cobs may be procured.

The corn-crop of North America varies; but, taking the yield of 1871—1,100,000,000 bushels, at fourteen pounds of cobs to the bushel—this would yield 7,700,000 tons of cobs, containing an average of three quarters per cent of pure carbonate of potash. The enormous quantity of 115,500,000 pounds of that useful article might thus be thrown into commerce. In some districts, these corn-cobs are extensively used as fire-lighters, being dipped into a composition of resin and tar, and then dried.

It is only some twenty years now since glycerine, a by-product in the manufacture of soap and candles, has been produced on a commercial scale, but the quantity now made represents an annual value of nearly a quarter of a million sterling. Glycerine has thus attained to a position of considerable technical importance. The introduction of the stearine-candle industry and the efforts to utilize the heretofore waste products of the soap manufacture demonstrated its existence in considerable quantity. The important uses to which this substance is now applied are so numerous that it would be difficult to enumerate them.

There is a large consumption of cork-bark, in this and other countries (the quantity we import exceeds in value half a million sterling), and even in this direction the economizing of the waste is found profitable and useful. The suberine powder is made into cork carpets for floor-cloth, and it is even used by chemists in place of lycopodium, powdered rice, starch, etc. Old corks are collected, and cleaned with hydrochloric acid and hot water, so as to be used again. The Paris sewers are provided with gratings, and the corks thus collected are recut, and used again. All cork cuttings are useful for filling life-buoys, belts, jackets, and even beds.

In Europe, as much use has not been made of sea-weed as in China and Japan, where it forms a very large article of consumption for food. In China, it is imported both from Japan and Asiatic Russia, to the