Feb. lo, 1876] 



NATURE 



295 



method was emplojed at Cologne in 187 1, * A company formed 

 in Paris for its employment had but a very brief existence,' pro- 

 bably owing to a similar discovery which soon supplanted the 

 one described above. 



This method, originated and perfected since 1867,' by 

 the invemive powers of M. Tessie du Motay, employs per- 

 oxide of manganese as the carrier of oxygen, and takes its 

 stand upon the following reactions. Sodic hydrate exposed to 

 dark red heat with manganese and air, yields, as Mitscherlich 

 discovered, manganate of sodium and water, 4NaOH + 2Mn02 

 -}- 2O = 2 Na.,MnO^ + 2H2O ; and manganate of sodium, 

 imder the influence of a dry current of overheated steam, disen- 

 gages at the same temperature sodic hydrate, manganic sesqui- 

 oxide, and free oxygen, 2Na2MnO^ + 2HjO = 4NaOH + Mn, 

 O3 + 3O. By pre^ously depriving the overheated air of its 

 carbonic acid, one may preserve the mixture in a perpetually 

 active state. This method has been thoroughly tested and ap- 

 proved, and has since been employed on a large scale in Comines, 

 near Lille ; in Pantin, near Paris ; in New York, in Brussels, 

 and in Vienna. Bothe * informs us that a mixture of sixty parts 

 of dry carbonate of sodium with forty parts of 95 per cent, per- 

 oxide of manganese, when fused, contains 74 62 parts of man- 

 ganate of sodium, and that 40 kilogs. of this nuxture, which, 

 according to calculation, should give 2,036 cb.m. of oxygen gas, 

 produced in reality 1,800 cb.m., or 90 per cent, of the theoretical 

 yield. He recommends the proceeding as a very practical one. 

 M. Pourcel '" has given us the most detailed description. Ac- 

 cording to him, M. Tessie du Motay employs cast-iron ellip- 

 soidal Retorts, which lie horizontally one beside the other, and 

 are divided by a grating parallel to their axes, into two unequal 

 parts. Over the grating 350 kilc^. of manganate of sodium, or of 

 the reduced mixture ot manganese and soda, are so spread out 

 that its height amounts to 060 m., and the empty space above 

 and below the mass is as inconsiderable as possible. In 

 Comines, where five of these retorts are used, the amount 

 of oxygen produced daily is 140 cb.m. at the cost of 450 kilogs. 

 of coals for heating the retorts, and of 150 kilogs. used for 

 the steam-engine. The air is passed through a thin iron 

 vessel with quick-lime by means of the bellows, under a pressure 

 of fr jm 3 to 4 cm. of mercury, and enters the retort from above. 

 The temperature of the latter can be observed through a hole 

 provided with an iron stopper. In this way the air gives off 

 only about half of its oxygen, so that to produce I vol. of oxygen 

 10 vol. of air must be passed through, the remainder escaping 

 into the atmosphere. Five minutes suffice for oxidising the 

 reduced mass. The current of air is then interrupted by means 

 of a three-way stopcock and superheated steam passed through 

 the retorts for five minutes, while the gas, passing out below the 

 grating, enters condensers. Here a fine rain of cold water frees 

 the oxygen from the steam, and the gas enters the gasometer 

 under the pressure of a column of water of from 8 to 10 cm. in 

 height. Thus reduction and oxidation alternate at inter\-als of five 

 minutes. After a lapse of six hours only, it is necessary, for a 

 perfect regeneration of the fused mass, to admit atmospheric air 

 for about an hour, because the quantity of oxygen obtained 

 becomes lowered after five or six hours, down to half or even a 

 third part of the original quantit}'. In Vienna the cocks are 

 worked by an automatic apparatus. The longer the steam is 

 forced in and the retorts freed from air before the communication 

 with the gasometer is opened, the purer will be the oxygen ; 

 half a minute is enough to leave oaly 15 per cent, of nitrogen 

 mixed with it, proN-ided the injurious space in the retort be kept 

 as small as possible. If the nitrogen be lowered to 4 per cent, 

 which is easily effected, the sacrifice of oxygen will be so much 

 the greater. To make certain that the quantity of nitrogen 

 remains within the limits of 15 and 10 per cent, which are proved 

 to be the most practicable, gas is taken from the gasometer or 

 the condenser in graduated tubes, and the oxygen is absorbed 

 by means of pyrogallate of potassium, a reaction attended by 

 quick and sure results, even in unpractised hands. 



As every cooling dow-n of the retort below dark red heat lessens 

 the yield, care is necessary to raise the temperature of the air, as 

 well as of the steam, to about 300' C. In Pantin, where several 

 groups of ten retorts are set up, two of them are fill jd with 

 pnmice-stone to warm the air and the steam. The composi- 

 tion of the fused mass corresponds to 2 moL NaOH, 1 moL 

 , MnOj, and the fifth part of a mol. of cupric oxide, which serves 

 ' • Philipps, " Der Sauerstoff," Berlin, 1871, aa. 

 Wagn. Jahiesbcr., 1867, 315. 



* Tessie du Motay, Institut 1868, 48. 



* Bothe, Zeitschr. d. Vereios deutch. Ing., 1867, 3J4. 



* Poured, " M6moire* debt SocJet6 des Ing^curs Civils." Paris, 1873. 



only to disintegrate the mass and make it more accessible to the 

 influence of the air and steam. In Comines peroxide of man- 

 ganese is reproduced from the residues of chlorine by the known 

 methods, almost in a pure state. Its market-pnce, for which the 

 Pantin works buy it, amounts to 2 fr. per kilog. The high price of 

 this basis of the manufacture of oxygen is indifferent, as it can be 

 tised continuously, and the longer, the more carefully the air is 

 kept free from carbonic acid. If, through some unavoidable 

 interruption of the manufactory, the mass should have attracted 

 carbonic acid from the atmosphere, it suffices to bring it to a red 

 heat, and pass steam over it until the steam, on leaving the retorts, 

 produces no precipitates in lime-water : then hot air paissed over 

 it will restore the mass to its original efiiciency. On an average, 

 a retort is said to last about a year. 



M. Tessie du Motay's method produces a cubic metre of 90 per 

 cent of oxgyen for 1 5 to 30 centimes,^ or, according to the results 

 of Herr Kuppslwieser's experiments,' 1,000 cubic feet at 3 fr., a 

 price in accordance with the last-mentioned sum, and scarcely 

 exceeding that of coal-gas. We may regard this method as a 

 final and successful solution of the problem of discovering 

 economical and rational chemical means for obtaining oxygen. 

 {^To be continued.') 



NOTES 



The Wollaston Medal of the Geological Society has been 

 awarded to Prof. Huxley, and will be presented at the Anniver- 

 sary of the Society on the iSth inst. Prof. Huxley has also been 

 elected a Corresponding Member of the Danish Academy of 

 Sciences. 



The Times of yesterday contains a summary account of what 

 has been done so/ar in this and foreign countries towards organ- 

 ising the Loan Collection of Scientific Instruments to be opened 

 at South Kensington in April. The invitation from the Science 

 and Art Department has met with a hearty response both in this 

 country and from foreign Governments. We last week gave a 

 list of the Foreign Committees, and the Times publishes the list 

 of those on the English Committees in the various departments 

 of Mechanics, Physics, Chemistry, Geology, and Biology ; and 

 as the Times remarks : "By going over them not only does one 

 get an idea of the disinterested way in which men — for the 

 most part busy men — have come forward to help the Depart- 

 ment, but there can be no better guarantee of. the success of the 

 Exhibition than that afforded by the list of those who are labour- 

 ing to make it successful." It would indeed; be difficult to^men- 

 tion any man of scientific eminence in this country whose name is 

 not included in the list. Out of England, as our readers would 

 see from last week's list, the most numerous committee is the 

 German one. On this the Times says : — " The German list gives 

 us much food for thought It is known, for instance, that the 

 thirty-four local committees, representing her many Univer- 

 sities, Polytechnic Schools, and other scientific centres, were 

 all organised in a week, and that her L'niversities will, 

 in all probabilitj-, be the richest contributors, whereas when we 

 have mentioned Edinburgh, Glasgow, Manchester, Birmingham, 

 Leeds, and Liverpool, and perhaps Newcastle, we have almost 

 exhausted the localities where committees would be useful." 

 The teaching side of the collection will be complete beyond all 

 anticipation. The Physical Cabinet, it is stated, will be such as 

 the world has never seen, towards the formation of which not 

 only will British, French, German, Italian, and Austrian instru- 

 ment makers lend their aid, but the collections of the Royal 

 Institution, Glasgow University, Edinburgh University, King's 

 CoU^e, the Conservatoire des Arts et Metiers, the Collie de 

 France, the Universities of Berlin, Bonn, Heidelberg, Leipsic, 

 Vieima, Rome, and Leyden, and the Tayler Institution at 

 Haarlem, and the like, will be ransacked. The Chemical and 

 Historical Collections will be of scarcely less magnitude. With 

 r^ard to the last it is still doubtiiil whether Italy will part with 

 Galileo's telescope and magnet, even for a month, though it is 



' Philipps, " Der Sauerstoff," 18. 



» Kuppelwieser, Berg-u. Hurtcn. Zeitung, 1873, 354. 



