Oct. 7, 1880] 



NATURE 



543 



10 to 20 per cent, of the change is completed, then more rapidly 

 until about 60 per cent, is reached, and then again slowly. He 

 also shows that the greater the molecular weight of the acid the 

 more rapidly is the period of maximum action reached. In 

 these phenomena we have fresh examples of the so-called 

 " Chemical Induction " of Bunsen and Roscoe. This supposed 

 special phase of chemical change would indeed appear to be of 

 very frequent occurrence, being only absent in those changes — 

 if such exist — which consist of a single part, the direct change 

 only. 



Berthelot, in the Comptes rendus of the Paris Academy, 

 describes experiments which lead him to believe that by the 

 electrolysis of dilute sulphuric acid a new oxide of sulphur — 

 S2O7 — is produced. This substance belongs to the class of 

 peroxides, and is analogous with ozone and hydrogen peroxide ; 

 the formation of each of these substances is attended with 

 absorption of heat. From the study of the thermal changes 

 accompanying the solution of ciilorine in aqueous hydrochloric 

 acid and in water, the same author thinks that a trichloride of 

 hydrogen, HCI3, probably exists. 



BoussiNGAULT, in Annales Chiin. Phys., has examined the 

 action of heat on Ijarium dioxide under diminished pressure, and 

 has shown that in a vacuum this substance parts with oxygen at 

 a low red heat, and that oxygen is readily absorbed from the 

 atmosphere by the bar)'ta thus produced at about the same tem- 

 perature, under ordinary pressures. It seems therefore that 

 baryta may be employed as a carrier of oxygen from the atmo- 

 sphere ; hitherto the high temperature required for the decom- 

 position of barium dioxide has brought about some molecular 

 change in the baryta produced, which has rendered it incapable 

 of absorbing more than very small quantities of oxygen from the 

 atmosphere. 



In Comptes rendiis, Hautefeuille states that he has obtained 

 crystals of orthoclase and of quartz in the same tube by heating 

 a mixture of acid potassium phosphate — previously fused with 

 silica and alumina — with silica and a little potassium fluosilicate 

 in a glass tube. 



Radziszewski in Liebig's Annalen gives a careful study of 

 the conditions under which various carbon compounds exhibit 

 phosphorescence ; he concludes that this phenomenon occurs 

 with those compounds which combine, in presence of alkalis, 

 with the active oxygen of ozone or other peroxide. Phosphor- 

 escence he regards as a special case of the phenomenon of 

 combustion ; during slow oxidation active oxygen is produced ; 

 hence it is in such processes of oxidation that phosphorescence is 

 noticed. When oxidation is rapid much of the active modifica- 

 tion of oxygen is produced, combination occurs rapidly between 

 this and the oxidising substance, and we have the phenomenon 

 of combustion. The phosphorescence of certain organised crea- 

 tures is due. according to the author, to the slow oxidation, by 

 the agency of active oxygen, of such compounds as lecithin, 

 cholesterin, spermacetti, myricylic alcohol, sugar, fats, or ethereal 

 oils. He shows that these substances are decomposed by cholin 

 and neurin, and generally by bases of the formula R4. N . OH 

 (where R is a monovalent alcoholic radicle, e.g., CH3.QH5, 

 &c.), and that this decomposition is attended with phosphor- 

 escence. 



A SMALL pamphlet, "Report on Two Kinds of Coal sub- 

 mitted by the Chesapeake and Ohio Railroad Coal Agency," 

 published by the Bureau of Steam-Engineering of the U.S. 

 Navy Department, contains a detailed account of the methods of 

 determining on the large scale the relative ratios of steam coals, 

 which must be of very considerable service to any who require 

 to perform such determinations. 



If aluminium hydrate, optained by precipitating a solution of 

 alum by ammonia, be allowed to remain in contact with water 

 for three or four months, it undergoes, according to M. Tom- 

 masi (CompU-s rendus), a molecular change whereby it is rendered 

 very much less soluble in acids, and is no longer capable of 

 forming a compound with aluminium chloride. 



PHYSICAL NOTES 



The conditions of geysers are investigated at length by Herr 

 Otto Lang in a recent paper to the Gottingen Society of 

 Sciences {Nachr., No. 6). The theory of Bunseu he considers 

 inadequate, and lie proposes another, which has an interesting 

 similarity to that of Mr. Mallet regarding the mechanism of the 

 intermittent volcano at Stromboli. 



Observations as to the changes of length of iron bars 

 through magnetisation having been somewhat discordant. Prof. 

 Right has lately taken up the subject afresh (// Ntimo Cim., 

 ser. 3, tom, vii.), and, to measure the displacements, he attached 

 a fine steel spring, with mirror, to one end of the bar (which 

 was magnetised by means of a spiral), the mirror being observed 

 through a telescope. Changes in length were thus magnified 

 8,000 times. The results were as follows : — i. Magnetism pro- 

 duces in iron and steel an increase of dimension in direction of 

 the magnetisation. 2. On cessation of the magnetising force a 

 part of this increase remains, and more or less of it according to 

 the coercive force. 3. The elongations are proportional to the 

 square of the current's intensity when this is not very great. 

 4. When, after a strong current through the spiral, a weak current 

 is sent in the opposite direction, it produces a shortening ; but 

 even when it is strong enough to demagnetise the bar, the latter 

 retains a greater length than in the normal state. 5. During 

 reversal of the polarity of a bar its length becomes momentarily 

 less, and it oscillates in length. 6. A bar or wire of iron tra- 

 versed by a current contracts at the moment of closing the 

 circuit. 7. On opening the circuit it elongates, but this elonga- 

 tion is less than the initial contraction, indicating that transverse 

 magnetism partly re.iiains. 8. In reversal of the transverse 

 polarity the bar elongates for a moment, and thus oscillates [in 

 length. 9. The contraction produced by the current is greater 

 when the bar has before been longitudinally magnetised. 10. 

 Some iron bars show a tendency to take spiral magnetisation, 

 i.e. to rotate the magnetic axes of their molecules in the direction 

 of the spiral. This is shown by the contractions caused by a 

 current passing through the bars, which are different according 

 to the direction of the current and that of the previous .longi- 

 tudinal magnetisation. 



The absorption of radiant heat in gases and vapours form th 

 subject of a recent valuable paper to the Vienna Academy 

 (July i) by Messrs. Lecher and Pernter. They consider "vapor- 

 hesion " to have been an important source of error in Tyndall's 

 experiments. In their own method the thermopile and the heat- 

 source were brought into the same vessel. Air-currents were 

 avoided by causing the surface of radiation to be heated in each 

 case suddenly from without, by means of a steam jet, to 100° C. 

 Among other results the absorption of water-vapour is found, in 

 opposition to Tyndall, immeasurably small. VioUe found, on 

 Mont Blanc, that a metre of the air absorbed only o'ooy percent, 

 of the whole radiation ; according to this, a layer of 300 m. 

 length would be necessary to produce, with water-vapour satu- 

 rated at 12', that absorption which Tyndall obtains in I '22 m. 

 This and the authors' own experimental results are considered to 

 prove beyond dispute the very small absorption of aqueous 

 vapour. The authors' results for gases agree pretty well with 

 Tyndall's. No simple connection betwesn absorption and pres- 

 sure of the substance was discoverable. The absorption, even for 

 radialion of a heat-source of 100° C, is selective. The authors 

 found the absorption of certain substances of the fat series 

 examined to increase rapidly with increasing proportion of 

 carbon. It seems to be otherwise, however, with bodies from 

 other groups ; thus, e.g. benzol, notwithstanding its six C-atoms, 

 has a fairly small absorptive power. 



Messrs. A. P. Laurie and C. I. Bruton of Edinburgh have 

 devi^ed a new electromotor engine, in which four electromagnets 

 act successively upon an eccentric armature of soft iron rotating 

 about a central shaft, thus avoiding the back pull of Froment's 

 and other forms of electromotor. The gradual approach thereby 

 secured between the armature and the active field-magnets is a 

 feature common to this engine and to that of Mr. Wiesendanger. 

 The principle has long been applied, though somewhat dif- 

 ferently, in the little motors employed for whirling Geissler's 

 tubes. 



SiG.NOR Macaluso has recently described a new form of 

 mercurial air-pump, on the Sprengel principle, .sufficiently simple 

 to be capable of construction from the materials at hand in any 

 chemical laboratory, and requiring no india-mbber coimections. 

 An outline diagram of the pump is given in the August number 

 of the Beibldtter. 



IIerr A. ScHERTEL has determined the fusing-points of a 

 number of difficultly-fusible substances by comparing them with 

 those alloys of gold and platinum in various proportions. He 

 gives the fusion-point of basalt as 1,166° C; that of adularia 

 (from the St. Gotthardt) is stated as being between 1,400° and 

 1,420° ; and nickel between 1,392° and 1,420°. 



