NATURE 



[June 7, 1900 



ADVANCEMENT OF ELECTRICAL 

 CHEMISTRY. 



TN a previous article (March i, p, 428) upon the advancement 

 -*■ of electrical chemistry, various developments of electro- 

 metallurgy or electrical deposition of metals were described. 

 Electrolytic processes for obtaining the non-metallic elements 

 and for the preparation of inorganic and organic compounds 

 were left for consideration in a separate article, and are now 

 dealt with. 



In the year 1800, Nicholson and Carlisle showed that water 

 could be decomposed into oxygen and hydrogen by means of a 

 " volta pile " ; since that time the electrolytic decomposition of 

 water has been employed as a lecture experiment to show the 

 composition of water. It is, however, only quite recently that 

 oxygen and hydrogen have been produced on a manufacturing 

 scale by the electrolysis of dilute solutions of caustic soda or 

 sulphuric acid. The hydrogen so obtained is usually almost 

 absolutely pure, but the oxygen is generally mixed with about 

 3 per cent, of hydrogen, which, however, can be removed by 

 passing it through red-hot tubes. 



The powerful oxidising action of ozone has through the ad- 

 vancement of electrical science been pressed into the service of 

 the manufacturer. The methods employed for its production 

 are all more or less based upon the well-known Siemen's tube. 

 Generally speaking, air and not oxygen is ozonised, the air to 

 be ozonised being freed from dust and from excess of moisture, 

 the last of which causes formation of hydrogen peroxide. The 

 temperature should be kept as low as possible, because at low 

 temperatures oxides of nitrogen are less liable to be formed and 

 the quantity of atmospheric oxygen converted into ozone is 

 increased ; indeed, some manufactuters cool the air down to 

 4° C. before subjecting it to the electric discharge. For con- 

 venience of use the ozone is generally compressed into iron 

 cylinders under a pressure of from four to five atmospheres. It 

 is used for refining and bleaching linseed and palm oils, and for 

 the manufacture of oxidised oil for linoleum. Brewers are often 

 troubled with fouling of the beer barrels ; this seems to be due 

 to the growth of a fungus which often penetrates the wood to a 

 considerable depth, so that ordinary methods of cleansing fail to 

 remove it. The oxidising action of ozone has been successfully 

 employed to remove this growth, the method being to alternately 

 steam and ozonise the casks. It has also been utilised to remove 

 fusel oil from alcohol, in the purifying of water, the refining of 

 sugar in place of animal charcoal, and in a great variety of other 

 manufacturing processes. 



It is well known that synthetical diamonds have been obtained 

 Dy means of the electric furnace ; charcoal obtained from sugar 

 is rammed into a wrought iron cylinder, which is then closed 

 with a plug. The cylinder so filled is placed in a bath of molten 

 iron kept at a high temperature in an electric furnace, after 

 which the crucible which contains the iron is rapidly cooled by 

 immersion in melted lead. On dissolving the iron in acid 

 minute diamonds are obtained. It was a question whether here 

 we had a case of simple crystallisation of the carbon from the 

 molten metal on cooling, or whether the enormous pressure 

 which was exerted upon the interior of the mass by the rapid 

 cooling of the outside acting upon the carbon at a high tempera- 

 ture caused the formation of crystals of diamond. An ex- 

 ceedingly ingenious experiment which has been carried out by 

 Majorana shows that at any rate the influence of high pressure 

 and high temperature combined is sufficient to convert amorphous 

 carbon into the crystalline variety. Majorana's experiment is 

 as follows : — 



A cylindrical chamber, A (Fig. i), is hermetically closed at 

 the top by a soHd block of iron, E, the bottom by a solid piston, 

 s. The sides of the chamber are made of tempered steel, and 

 to further strengthen it the chamber is surrounded by fifteen 

 iron rings i cm. thick, which are bolted together. The whole 

 system is placed within an hexagonal frame, K, also made from 

 iron plates. The piston, s, has a small solid iron cylinder about 

 I cm. in diameter attached to it, at the end of which is fastened 

 a small piece of carbon, c, about 2 grms. in weight. Directly 

 below the piston a thick block of iron, /, is fixed, into which a 

 hole exactly the size of the small end of the cylinder has been 

 drilled. In carrying out the experiment the carbon is heated 

 by means of the two carbon poles, D, d', with a current of 25 

 amperes and 100 volts. When the carbon has become white- 

 hot, 70 grms. of gunpowder contained in the chamber A is 

 exploded, the piston being driven down, carrying the heated 



'^'O- 1597. '^OL. 62] 



carbon before it and compressing it with enormous force. On 

 taking the system to pieces the carbon is found to have been 

 partially converted into microscopic diamonds, which when 

 freed from unchanged amorphous carbon are found to possess 

 all the characteristics of natural diamonds. 



Reference has already been made to the importance of the 

 manufacture of calcium carbide ; another carbide, that of silicon, 

 is now being manufactured in considerable quantities, and, 

 owing to its extreme hardness, is being employed in place of 

 emery for polishing steel and making grindstones. This 

 carbide, which goes under the name of "carborundum," is 

 manufactured by means of the electric furnace. An American 

 company at Niagara Falls employs furnaces capable of dealing 

 with ten tons of p^aterial, consisting of coke, sand, common 

 salt and sawdust, which yield two tons of carborundum in 

 twenty-four hours.' In the first half of the year 1897 it is stated 

 that in America alone 750,000 lbs. of carborundum were manu- 

 factured. Since the introduction of electricity to chemistry the 

 carbides of almost all the metals have been obtained, the 

 majority naturally being more of theoretical than of commercial 

 interest. 



From the days of Leblanc, the founder of the soda industry, 

 perhaps no branch of inorganic chemistry has been more worked 

 at, or has better shown the results of patient toil and inventive 

 genius, than the alkali and bleaching industry. Only after many 

 attempts and many failures has the seemingly simple task of 

 electrolysing sodium and potassium chloride yielded results 



which have enabled electricity to enter into competition with the 

 former methods of manufacture. 



According to the manner in which the electrolysis is con- 

 ducted, a solution of potassium chloride may be converted into 

 chlorine and caustic potash, potassium hypochlorite, or into 

 potassium chlorate. If the electrolysis takes place at low 

 temperatures, a solution of hypochlorite is obtained, which may 

 without further treatment be used for bleaching purposes. The 

 difference in price between this solution and a solution of bleach- 

 ing powder is not very great, but the greater cleanliness and 

 purer bleaching action of potassium (sodium) hypochlorite make 

 it, when electric power can be easily obtained, at least a power- 

 ful competitor with bleaching powder. When the electrolysis 

 is conducted at temperatures from 60° and upwards, the bath 

 being kept slightly alkaline by addition of potassium bicarbonate 

 or lime, potassium chlorate is produced, which, owing to its 

 slight solubility in water, crystallises out, and by washing 

 readily freed from adhering chloride. 



If caustic potash and chlorine are required, some aro^angement 

 must be made to prevent the liberated chlorine from again 

 reacting with the caustic potash formed at the same time. 

 Formerly, and still to a small extent, this was arranged by 

 means of a diaphragm which separated the anode from the 

 kathode. Owing, however, to the difficulty of obtaining a 

 pervious impervious diaphragm, i.e. one which allows the current 

 to pass, but is impervious to the solution, it is now more 

 general to electrolyse without a diaphragm. The method em- 

 ployed is one which was originally employed by Castner and 



