RAW material and energy, these are the two essential factors which go to make up every industrial chemical process. with the exception of the rare gases of the atmosphere, every object around us is susceptible of chemical change, and hence available to a greater or less extent as raw material for some chemical process. The possibilities of the chemist are in this direction unlimited. The second factor, energy, was for many years supplied almost exclusively in the form of heat derived from the combustion of some kind of fuel, and thus limited in many ways the chemists activity. It is only within the last quarter of a century that there has been supplied to the manufacturer in commercial quantities, a new form of energy, namely, electricity. With the development of powerful electric generators harnessed to great sources of water power there has been rendered available a form of energy destined to play an important part in the industrial development of the country when chemical change is brought about by tle application of electric energy, we have an electrochemical process; and the art is called electrochemistry. It would have little value simply to catalogue the many successful applications of electrochemistry which have been worked out, or to describe the great industrial plants based on electrochemical processes which have grown up in America within the last decade. Rather we will attempt to point out some of the principles underlying the application of electricity to chemical industry, and to give a few examples illustrative of each general class. Electric Conductance and DecOinposition.-when a chemical substance such as common salt or blue vitriol is dissolved in water, it is, for the most part broken up or separated into electrically charged atoms or groups of atoms called ions. When a current of electricity from some external source is led into such a solution, it is transported through the solution by these ions. At the points where the current enters Rnd leaves the solution (i. e., the electrodes) these ions are deposited and take from the current the electrical energy necessary to change them into the corresponding elements or compounds. Thus when an electric current is passed through a solution of blue vitriol (copper sul- phate) metallic copper separates out where the current leaves the bath, and sulphuric acid is formed at the other, or entering, electrode. This ability of the electric current to decompose chemical compounds into their constituent parts is called electrolysis, and forms the basis of many important industries. ElectrolYSiS of Salt.-Common salt, sodium chloride, is one of the cheapest as well as one of the most important of our chemical raw materials. From it through intricate and expensive processes there has been made for centuries the . austic soda and soda ash used in a hundred industries, such as the manufacture of glass, soap and textiles. At the same time from this salt by another complicated process the bleaching powder of commerce was produced. Electrochemistry has changed all this. At present by simply passing a heavy current of electricity through a strong salt solution, caustic soda is produced and drawn off at one electrode, and chlorine gas, which when absorbed by common lime makes bleaching powder, is evolved at the other. Compared with the older processes, this electrolytic one is simplicity itself. Although there are many' millions of dollars invested in the old processes, the time is rapidly coming when they must give wry to the new. In a very similar way, namely, by passing a current of electricity through a hot solution of potassium chloride (the “muriate” of commerce) and allowing the two products formed at the electrodes to react on each other, is formed the potassium chlorate used in such large quantities in making all kinds of matches. 'his electrolytic process is carried on at a number of places in the United States and has entirely superseded the old method of making this important chemical. Refining of letals.-On this same principle depends the enormously important industry of the electrolytic refining of copper. by which during last year alone something over $100,000,000 worth of pure copper was prepared for the market, besides the recovery of several millions dollars' worth of silver and golL from the waste. The crude or raw copper is cast into slabs which are made the entering electrode (rnode) for a heavy electric current passing through a copper sulphate solution. Pure copper is deposited from the copper sulphate solution on a very thin sheet of pure cop- per which forms the outgoing electrode (cathode), while the sulphuric acid set free dissolves from the crude copper electrode an amount of metallic copper equivalent to the pure copper deposited upon the cathode. The supply of copper sulphate solution 1' thus kept constant. By maintaining the conditions within certain limits the current is selective in its action, transporting only the pure copper from the crude slab or ingot over to the other electrode where it a,ears as chemically pure metal. Similar methods are used for refining other metals such as silver, etc. Metal Plating.-All electro-plating is done by the use of the electric method just described. If we imagine the impure metal anode replaced by a pure metal one, be it of copper, nickel, silver or gold, and the cathode sheet replaced by the object to be electro-plated, we have reproduced a plating bath. Objects of great size such as tubing and conduit pipes are now covered with zinc in this way. Electrotyping is but a variation of the same process. Metallic Aluminilr and Sodium.—Certain molten compounds have the property of conducting the electric current and of breading up at the electrodes just as salts in water solution do. Of special importance in this connection and depending upon this fact is the preparation of the metals sodium, magnesium and alummium. When a current is passed through molten caustic soda for example tilis compound is broken up. the metallic sodiulll separating at the cathode and the remainder of the molecule, oxygen and water vapor, passing out into the air. The molten, sodium is cast into ingots and preserved under petroleum oil. It is of great use to the chemist and is now made at about one-fourth the cost of what it could formerly be produced for by strictly chemical means. But of much greater importance is the manufaeture of aluminium, a metal more abundant than iron, and especially noted for its lightness and silver-like appearance. For many years chemIsts had searched for a cheap method for producing aluminium inasmuch as it is more abundant on the earth's surface than any other metal, and although the price had been reduced from five dollars per pound it could not be made by' chemical (Contvnued on page 2;)2.) 214 SCIENTIFIC AMERICAN September 16, J!lJ i SCIENTIFIC AMERICAN Founded 1845 NEW YORK, SATURDAY, SEPTEMBER 16, 1911 PUbliished ?y lU.I.lm& Co.. Incorporated. Uhal'les AilellMunll. Presidf!lJt: rIedericl Converse Beach, secrerary anl Treasurer; all at oBl Broauway, New York KntNed “t tlie 1'ost Office of !ew lork. N. Y.. as Second Class Matt;; Copyright lOll by MUln&Co. . inc. 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