346 



NATURE 



[November 21, 1912 



sities of our industry, namely copper, is largely purified 

 by electrical means. Aluminium, calcium carbide, 

 carborundum, sodium, and potassium are wliolly pre- 

 pared electrically. The only hydroelectric stations of 

 any size that have been built in this country are used 

 for electrochemical purposes. The pi:oduction of 

 aluminium alone at Loch Leven absorbs some 

 jo.ooo kw. 



The production of disinfectants electrolytically is 

 being worked on a small scale. In Poplar the forma- 

 tion of a solution of chlorine in water by means of 

 electrolysis is in practical use. Although one cannot 

 anticipate very large powers being required for this 

 purpose, yet if the demand for electrolytic disinfec- 

 tants all over the country was the same as in Poplar, 

 it would require about 2,000,000 units per annum, all 

 of which could be supplied at such times as would 

 help to level up the load curve. 



Electromedical apparatus. — The design of induction 

 coils for the production of X-rays has advanced a long 

 way of late years, and some of the latest pieces 

 of apparatus for the production of the discharge 

 through the X-ray tube involve considerable ingenuity 

 and engineering design. The discharge must be un- 

 directional and at a high pressure, say, 50,000 volts 

 or more. One method to obtain this is to step up by 

 means of an E.H.T. transformer and to rectify the 

 secondary current. Another method of working to 

 obtain practically instantaneous photographs consists 

 in switching the primary of the transformer straight 

 on to the direct-current mains, when the current 

 rush instantly blows the fuses. This interruption of 

 the current produces one powerful discharge on the 

 secondary, which, passing through the X-ray tube, 

 suffices for the photograph. I do not know how the 

 supply companies view this method of operation, be- 

 cause the rush of current must be prettv considerable, 

 as the apparatus is not constructed on' a particularly 

 small scale. The transformer weighs about half a ton. 



Electricity and Chemistry. — We are all of us 

 acquainted with the brush discharge, vet how much 

 do we know of its mechanism? In oiir high-tension 

 rnachinery w-e are mainly occupied with trying to get 

 rid of it and its injurious effects. Yet it has its uses. 

 Nearly all the information in our proceedings deals 

 with the negative question, namely how to avoid it. 



Now_ the brush discharge has a peculiar property of 

 producing that modification of oxygen known as 

 ozone, which is without doubt a strong sterilising 

 agent, and which may in the future have "considerable 

 applications. A modification of the conditions of the 

 production of the disciiarge will cause the formation 

 of oxides of nitrogen instead of oxides of oxygen. 

 Oxides of nitrogen are of great commercial irnport- 

 ance, and their production by electrical means will 

 probably be one of the most important industrial 

 applications of electricity. 



Already in Norway between 100,000 and 120,000 kw. 

 are employed working day and night for this purpose, 

 and it is stated that this power will shortly be in- 

 creased to nearly 2.50,000 kw. The main object of 

 fixing the atmospheric nitrogen is to form a substance 

 to replace Chile saltpetre. " The demand for this is 

 yearly growing at an increasing rate. 



Last year about 125,000 tons of nitrate were im- 

 ported into this country. To produce the equivalent 

 amount of fixed nitrogen per annum would, on the 

 basis of Norwegian plants, require about 150,000 kw. 



.At the moment I believe that the cost of electrical 

 power is the chief stumbling-block to the introduction 

 of the manufacture on a large scale in this country. 



Klect'ricitv and Sound. — I do not know of many 

 researches on the efficiency of the telephone receiver, 

 vet the question is reallv a practical one and of con- 



xo. 2247, VOL. go] 



siderable importance, ihe telephone receiver may be 

 looked upon as an alternating-current motor. It 

 receives electrical energy, which it converts into the 

 mechanical form in the motion of its diaphragm, 

 which energy is transmitted to tlie air as sound 

 waves. There is no special difficulty in measuring 

 the electrical energy supplied to the telephone receiver 

 to a moderate degree of accuracy. The amount of 

 this energy that is transmitted to the diaphragm is 

 much more difficult to estimate. The real difficulty is 

 the determination of the amount of energy of the 

 sound waves. If we possessed any apparatus by 

 means of which we could measure energy of sound 

 waves we could not only determine the efficiency of 

 the telephone receiver, but the apparatus would have 

 many other useful applications. It is curious to thinli 

 that up to tlie present we have no unit or standard 

 of sound. We cannot specify its strength or intensity. 

 Even the comparison of two sounds by the ear is 

 very inaccurate ; nowhere near as accurate as the 

 comparison of two lights by means of the eye. This 

 want of standards and methods of measurement is, 

 I believe, one of the causes that has retarded progress 

 in the science of sound. Can electricity, the hand- 

 maid of all the other sciences, help in this direction ? 



Electricity and Radiation. — Much work is quietly 

 going on, of which we in the institution hear nothing, 

 to try to unravel completely the mechanism of the 

 transfer of electricity through gases. There is much 

 to be hoped for along these lines. The elaborate 

 glass apparatus, the vacuum tubes, the mercury, the 

 liquid air, &c. , which are being used in the research 

 make the experiments look most unpromising from 

 the practical engineer's point of view. Yet some pro- 

 gress is being made in electric lighting by means of 

 the passage of electricity through gases. Many mem- 

 bers will remember the vacuum tube, 176 ft. long, 

 which w-as used to light the courtyard of the Savoy 

 Hotel. That tube, I believe, contained nitrogen, and 

 according to the tests of Prof. Fleming, gave an 

 efficiency of 056 candle per watt. About a year ago 

 I saw a tube, not such a long tube, filled with the 

 rare gas neon, obtained froin the residues in the 

 manufacture of liquid air. This tube gave a most 

 beautiful rose-coloured light. If this rare gas were 

 obtainable in sufficient quantities we might have a 

 rival to the flatne arc. I may mention in passing 

 that tubes containing neon are now commercially 

 obtainable, and are claimed, in the larger sizes, to 

 have an efficiency as high as two candle-power per 

 watt. Further researches on the borderland between 

 electricity and radiation will no doubt provide us with 

 still more efficient sources of light. 



We are at present very far from any practical means 

 of converting the energy of radiation directly into 

 electrical energy, although on a small scale this con- 

 version really takes place in many photoelectric ar- 

 rangements. For instance, the action of the light on 

 the liquid potassium sodium alloy has been shown by 

 Prof. Fleming to produce a voltage as high as o'6 volt 

 when the liquid allov and a platinum plate are enclosed 

 in a hifhlv exhausted tube, and the liquid" alloy is 

 illuminated strongly. There seems little doubt that 

 the current that is generated in this case is produced 

 from the energy of the light that is absorbed. 



The effects so far obtained are extremely small. At 

 the most onlv a few microamperes are obtainable with 

 verv strong illumination. Nevertheless, this property 

 of sensitiveness to light, though at the moment it has 

 no practical applications, mav at any time be found to 

 fill some useful purpose and make another case 

 illustratinc how observations that are one dav on the 

 borderland of science may shortly afterwards be of 

 practical use in engineering. 



