June 2, 1898] 



NATURE 



115 



iliaphragm may be dispensed with, according to Oettel, if the 

 solution is alkaline, because in that case potassium chlorate is 

 not reduced, to any appreciable extent, by nascent hydrogen. 

 High current density at the kathode, and low current density at 

 the anode, promote the formation of chlorate, the best results 

 being obtained when a quantity of oxygen is evolved, corre- 

 sponding to some 30 or 40 per cent, of the current passed. The 

 current efficiency is reported to be from 65 to 70 per cent., and 

 there is no doubt that the electrolytic process will eventually 

 displace the older chemical one, about one half of the world's 

 consumption of chlorates being already supplied by it. 



Of other electrolytic processes there is not very much to be said. 

 In Mr. A. B. Brown's process for the manufacture of whitelead 

 a 10 per cent, solution of sodium nitrate is electrolysed in order to 

 obtain caustic soda and nitric acid, which are subsequently used 

 for the preparation of lead nitrate and its precipitation as lead 

 hyilroxide, the latter being finally converted into lead carbonate 

 by means of a solution of sodium bicarbonate. 



Applications of electrolysis to tanning and to the purification 

 of sugar have been frequently proposed, but nothing very 

 definite is known as to their success. 



Among organic compounds iodoform has long been prepared 

 by the electrolysis of an alkaline solution of potassium iodide 

 containing alcohol. According to Elbs and Hertz good results 

 are obtained by electrolysing a solution containing 5 to 6 grams 

 of sodium carbonate, 10 grams of potassium iodide and 20 cc. 

 of alcohol in 100 cc. of water at a temperature of 60° C. with a 

 current density not exceeding i ampere per square decimetre. 

 Under these circumstances the current efficiency is over 97 per 

 cent, and the iodoform produced perfectly pure. 



It has been propo.sed to apply ozone to a great variety of 

 purposes, but here again a lack of trustworthy information about 

 the results is found. According to Mr. Swan, however, it is 

 used in making vanilin and heliotropin. When used as a 

 bleaching agent it is necessary to use it in conjunction with 

 other substances, such as hypochlorites or hydrogen peroxide. 

 Mr. Andreoli has devised an ozone producer in which the elec- 

 trodes are furnished with numerous points and separated by a 

 glass plate. In order to prevent the heating of the gas it is 

 caused to pass rapidly throught the apparatus, and the electrodes 

 are made hollow and cooled by internal .circulation of water. 

 The silent discharge is obtained by means of an alternating 

 current dynamo and high tension transformer yielding a rapidly 

 alternating current at a pressure of 10,000 volts or more. By 

 this means 30, or under favourable conditions 40 grams of ozone 

 are obtained for a horse-power hour. 



Electro-thermal Processes. — The electric current possesses two 

 considerable advantages as a heating agent ; in the first place 

 temperatures otherwise unattainable may be reached by its aid, 

 and secondly the heat may be applied directly and economically 

 to the substances which are to be caused to react. The three 

 most important products of the electric furnace are carborundum, 

 phosphorus, and calcium carbide. 



Carborundum, a compound of carbon and silicon in equal 

 atomic proportions, was prepared by Acheson in 189 1, in the 

 course of experiments on the artificial production of the diamond. 

 It is remarkable for its extreme hardness, which is only inferior 

 to that of the diamond. It is prepared by heating a mixture of 

 powdered coke and sand, to which a little sawdust and salt are 

 added in order to make the mass more porous, in a furnace 16 feet 

 long, 5 feet wide and 5 feet deep, which is built up of loose fire- 

 bricks. Through the end walls of the furnace bundles of 60 

 carbon rods, each 3 inches in diameter pass, which are connected | 

 inside the furnace by a cylindrical core of small pieces of coke. 

 This core is surrounded on all sides by the mixture of sand and 

 coke. The passage of the current through the core gives rise to 

 a cascade of small arcs between the pieces of coke, which soon 

 raises the whole core to a very high temperature which is 

 communicated to the surrounding charge. A current of 6000 

 amperes at 125 volts pressure is passed for 36 hours, after which 

 the furnace is allowed to cool and the hollow cylinder of crystal- 

 line carborundum surrounding the core removed. About 5*3 

 electrical horse-power hours are expended in producing a pound 

 of the crystalline product, a considerable quantity of valueless, 

 amorphous carbide of silicon being also formed at a greater 

 distance from the core, where the temperature is lower. The 

 carborundum is obtained in the form of steel grey to brownish 

 green crystals, the coloration being due to iron ; it is a valuable 

 abrasive, cutting the hardest steel without destroying its temper ; 

 and is being largely used in place of emery. The production 



NO. 1492, VOL. 58] 



has increased from 15,000 pounds in 1893, when it was first made 

 on a manufacturing scale, to about one and a half million pounds 

 in 1897. 



The manufacture of phosphorus in the electric furnace has 

 been carried on for some years by means of the process of Read- 

 mann and Parker and Robinson. Wcihler found, as long ago 

 as 1830, that pho.sphorus may be obtained from calcium phos- 

 phate by heating it to a high temperature with sand and carbon, 

 calcium silicate and carbon monoxide being produced. The 

 employment of the electric furnace has made it possible to use 

 this process for the manufacture of phosphorus. Naturally 

 occurring phosphates are used and siliceous material added, 

 which will furnish a readily fusible slag. The finely-powdered 

 mixture of these substances with carbon is fed in through a 

 hopper at the top of a brick-lined trough, 18 inches square and 

 36 inches deep, through opposite sides of which the carbon 

 electrodes are introduced. The fused slag collects at the bottom 

 of the furnace, whence it is run off from time to time in the same 

 way as in a blast furnace, whilst the mixture of phosphorus 

 vapour and carbonic oxide pass to the condensing apparatus 

 through an opening placed near the top of the furnace. More 

 than 80 per cent, of the phosphorus contained in the materials 

 used is obtained, the loss being largely due to the presence of 

 iron which combines with phosphorus to form a phosphide which 

 remains in the slag. The heat is concentrated mainly between 

 the electrodes, so that the walls of the furnace do not suffer. 



Calcium carbide was prepared by electrically heating together 

 carbon and lime, in 1892 by Moissan in France, and by Willson 

 in America ; its manufacture is now carried out on a very con- 

 siderable scale, both in America and in Europe. The production 

 is said to be about 20,000 tons yearly. The furnaces employed 

 vary considerably in details of construction and in magnitude. 

 Those employed at Niagara consist of a square brickwork shaft 

 in which a bundle of carbon rods, which forms one electrode, is 

 suspended. The bottom of the shaft is closed by an iron 

 rectangular box, running on rails, the bottom of which has a 

 thick lining of carbon, which serves as the other electrode. The 

 finely-powdered mixture of coke and lime is fed into the space 

 round the upper electrode through channels in the brickwork 

 sides of the shaft. The arc having been established between 

 the electrodes, the mixture of coke and lime is shaken down 

 into it, and converted into calcium carbide, which remains in a 

 semi-fluid condition upon the lower carbon plate. " The calcium 

 carbide, being a fairly good conductor of electricity, now serves 

 as the lower electrode, fresh material being constantly added to 

 its upper surface until the iron box is full, when it is run out 

 and a fresh one substituted for it. The current employed is 

 1700 to 2000 amperes, and the electromotive force 100 volts, a 

 pound of the carbide being obtained for an expenditure of 2*25 

 electrical horse-power hours. When sufficient carbon is em- 

 ployed in the mixture, the electrodes are very little acted upon ; 

 the excess of carbon which is required depends very much on 

 the kind of apparatus employed. A pound of well-made carbide 

 yields 5 cubic feet of acetylene gas, the employment of which for 

 lighting appears to be making some progress. 



In concluding this brief sketch of the applications of electro- 

 chemistry, it is perhaps worth pointing out that, important and 

 interesting as are the applications which have been made, those 

 which yet remain are still more so. For example, it is possible, 

 by compressing sulphur dioxide and air into separate carbon 

 tubes dipping in dilute sulphuric acid, to cause the two gases to 

 combine to form sulphuric acid, and at the same time furnish an 

 electric current. The alluring prospect of obtaining electric 

 energy as a bye-product in a chemical works, should be a suffi- 

 cient incentive to efforts to overcome the numerous difficulties 

 in the way. Thos. E\v.\n. 



THE STRANGLING OF AN ELEPHANT. 



ONE of the elephants in Barnum and Bailey's Show, which 

 has been visiting Liverpool during the past two weeks, 

 having recently shown signs of insubordination, Mr. Bailey 

 determined, in order to perfectly safeguard his visitors, to 

 sacrifice the animal. He has had during his life occasion to 

 destroy many elephants, which, as a rule, he has handed ovei 

 to experienced veterinary and other surgeons, who have tried 

 various methods, such as poisoning, shooting and bleeding. 

 All have proved, however, unsatisfactory, because uncertain, 

 tedious, and not seldom dangerous to those engaged in conduct- 



