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52

Retrospect of Medicine.

SCHEMICAL NEWS,

January si, 1879,

the hydrate of trimethyl-sulphine. On evaporating the Catalogue of Chemical Apparatus and Pure Chemicals solution of the salt on the water-bath it begins after a Sold by Townson and Mercer, 1879. time to crystallise out. On leaving the saturated solution A well compiled illustrated catalogue of every descrip. to cool a large quantity of clear cubical crystals were ob- tion of chemical and physical apparatus. We would tained. These are not hygroscopic, insoluble in hot especially direct the attention of students, teachers, alcohol, and without any smell of sulphide of methyl. I lecturers, and medical officers of health to the cheap sets These properties prove it to be one of the most stable of 1 of scientific apparatus described at the end of the book, the salts of trimethyl-sulphine. Analysis agrees with the which seem to be a speciality of this old-established firm. formula

There is an excellent index at the end of the catalogue. [(CH3)3S 12S206.H20. On heating the salt to about 120° water is given off. On raising the temperature to 220% sulphurous acid is

Practical Physics, Molecular Physics, and Sound. By given off, and afterwards along with it sulphide of methyl,

FREDERICK GUTHRIE, Ph.D., F.R.SS.L. and E., Proand the salt froths and melts. The heating at about 2000

fessor of Physics in the Royal School of Mines. was continued until very little gas was given off. 8.015

London : Longmans and Co., 1878. grms. were found to have lost 3.325 grms., equal to 414 This little work belongs to the excellent elementary per cent. On cooling the liquid solidified. The crystal series called the London Science Class Books now in line mass was very hygroscopic, and dissolved in alcohol. course of publication by Messrs. Longmans. The ar. On adding, ether to the alcoholic solution the substance rangement adopted by Prof. Guthrie is somewhat new. was precipitated as an aqueous syrup, and on standing After explaining the principles of molecular cohesion in over sulphuric acid crystallised out in beautiful long fine the case of solids, liquids, and gases he carries his pupil prismatic needles. The presence of the trimethyl-sulphine through diffusion, effusion, osmose dialysis, and vortex radical was proved by double decomposition with iodide motion, into wave motion in general, and lastly introof potassium, when the iodide of trimethyl-sulphine duces him to the principles of sound, thus rendering the crystallised out. The presence of methyl-sulphuric acid sequence complete, the string telephone and the phonowas also proved. These results, along with estimations graph being introduced as illustrations. There is a useful of carbon and hydrogen, prove the substance to be the appendix added explaining the use of the vernier, the methyl-sulphate of trimethyl-sulphine. The decomposition method of making parchment paper, hints on glass working, of the dithionate is therefore expressed by the following barometer making, &c. The experiments illustrating the equation :

lessons in the body of the work, and the apparatus and (CH3)39) S206.H20= (CH3)

materials used in performing them, are also explained at

s04+(CH3)2S+H20. (CH3)3st 2

greater length in a second appendix. A paper was also read by Mr. J. W. Drake on the Constitution of Inorganic Salts."

Notes of Statutes and Legal Decisions Affecting the

Public Health Act, 1875, from 1875 to 1878. By J. V.

Vesey FITZGERALD, B.A. London: Longmans and Co. THESE notes are intended by the author as a sequel to a former work on the same subject at the time of the

passing of the Public Health Act of 1875. To officers of Useful Information on Practical Electric Lighting. By health, inspectors of nuisances, factory inspectors, medical KILLINGWORTH HEDGES, C.E., M.I.M.E.

men, local boards, vestries, and all other bodies or indi. A POPULAR account of the principles, production, working,

viduals whose duty it is to see that the provisions of the

various health acts are duly carried out, this little work and in part the cost of the electric light, confessedly some what hastily thrown together. Mr. Hedges divides his

will prove invaluable. subject into nine sections. The introduction treats of the laws governing induced magnetic currents; the second The Retrospect of Medicine. Edited by W. BRAITHWAITE, chapter of the various kinds of electrodes and electric M.D., and James BRAITHWAITE, M.D. Vol. lxxviii., lamps ; the third is on the division of the electric light. July to December, 1878. London : Simpkin, Marshall, The kind and quantity of power required are con and Co., 1879. sidered, as well as the application of the light for illumina- As usual there is but little to interest the chemist in the tion. The transmission of electricity by wires is then present volume of Braithwaites' “ Retrospect," valuable explained, the approximate cost of working is neces as it may be from a purely medical point of view. A Dr. sarily somewhat incompletely dealt with, trustworthy Jencken, who hails from the Emerald Isle, recommends data being as yet wanting. Mr. Hedges, speaking as a gun-cotton as a dressing for wounds on account of the practical engineer, very properly ridicules the nonsense antiseptic character of the acids used in preparing it. We that has been written respecting the extin&tion of gas by should imagine that properly washed pyroxylen would electricity. The same prophecies were made with regard have no greater antiseptic power than ordinary cleaned to oil and candles when first gas was used. The electric cotton-wool, while if it still retained sufficient traces of light, says Mr. Hedges, will educate the public to a acid to possess antiseptic properties it would be a highly higher degree of artificial lighting, a prophecy al. | dangerous addition to hospital requisites. Of quite a ready fulfilled by the Phænix Gas Company, which has different calibre is Mr. Spencer Wells's warning to sur. lighted up the bridge end of Waterloo Road with a bril. geons-not too place to much confidence in the use of antiliancy hitherto unknown in the history of gas lighting. | septics in surgical operations at the risk of omitting any A higher standard of gas will be called for by shopkeepers, of the precautions which experience has declared to be and an increased, instead of a diminished, consumption of necessary; in a word, antiseptic treatment must not be gas will follow. We cannot, however, agree with Mr. looked upon as a substitute for measures which have Hedges when he thinks that we may obtain the electric already proved effectual, but only as an additional safe. light more economically from the battery than from the guard. Sir Henry Thompson gives an account of the dynamo-electric machine. Mr. Hedges promises to give use of the microphone in sounding for stone (July, 1878), us a second edition of his pamphlet. In the present edition but his experiments at present do not seem to have led he has been continually betrayed into the use of technical to any practical result. The use in psoriasis of crysoexpressions which, although perfectly familiar to all phanic acid, one of the few chemical remedies discovered scientific men, will be simply so much Sanscrit to the of late years, appears to be spreading. By the way, we ordinary reader.

may mention that a cheap method of preparing this acid

: NOTICES OF BOOKS.

News,

is a desideratum. It is related to anthracen, being con. | di Papa, near Rome, he had been able to distinguish three vertible into that substance when heated with zinc-dust, kinds of sounds, and to trace their relation with the movethe contrary operation, therefore, ought not to be imposments of his seismometers. sible. The only other papers of chemical interest are! Harmotome and Stilbite.-A. Gaudin.-The author those of Dr. Ogston, Jun, “On a Stale Solution of Am. monium Sulphide as a Test for Chloral; “On Butyl

gives diagrams to show the atomic arrangement of these chloral," by Liebreich, who finds that whereas in the case

minerals. of ordinary chloral hydrate the heart is paralysed before

Electro-chemical Action under Pressure. – A. the respiratory organs, the reverse held good in the case

Bouvet.-The author considers that he has established of butyl-chloral, a very singular and important physiolo

the two following laws:-That the decomposition of water gical observation; and “On the Advantage of Oxygen

by a current is independent of pressure. The quantity of Inhalation in Cases of Asphyxia from Breathing Carbonic

electricity necessary to decompose a given weight of water Acid.” Dr. R. H. Goolden announces that for thirty-five

is the same under whatever pressure the decomposition years he has used manganese sulphate with great success

is effected. in the treatment of liver complaint, but that a prejudice Liquefaction of Gases by MM. Cailletet and Pictet. exists against its use on account of the difficulty of getting

-A. Bouvet.—The writer points out that the principle it dispensed, pharmaceutists either never having the salt | made use of was indicated by him in a memoir addressed in stock or taking manganesiæ sulph. for magnesiæ sulph., to the Academy on October 8, 1877. and dispensing it accordingly. Dr. Goolden's efforts to Magnetic Rotation of the Plane of Polarisation og introduce this remedy deserve all praise, in spite of the Light under the Influence of the Earth.-J. Joubert: little success that he has hitherto met with. "The same -The author admits the reclamation of H. Becquerel remark applies to Dr. B. W. Richardson's endeavours to concerning the experiment described in his memoir of introduce the alkaline ethylates as caustics.

December 23.

Use of the Telephone and Microphone in Scientific

Researches.-M. Hughes.—These instruments may be CORRESPONDENCE.

advantageously employed, especially in researches concerning very feeble induction-currents resulting from the

movement of a magnet before a helix. INFLUENCE OF CHLOROFORM ON

A New Electric Lamp.-E. Ducretet,-The arrangeNITRIFICATION.

ment of the lamp cannot be described intelligibly without

the accompanying figure. Its principal peculiarity is the To the Editor of the Chemical News.

use of a mercurial column into which the points are

plunged. SIR,-In reply to Mr. Warington's letter, I must at once acknowledge that I used the term “ nitrification” in a

Existence of an Oxide of Nickel, Niz04.-H. Baustretched and, I fear, erroneous sense. I certainly am

bigny.-This oxide, unlike the corresponding iron com

pound, is not magnetic. It is formed on treating nickel of opinion, that in many cases “ the destruction and pro. duction of nitrates are allied phenomena, both of which

chloride at 440° with moist oxygen, and appears as a grey

metallic crystalline powder. It is slowly attacked by hot are due to the action of bacteria " or of similar organisms.

hydrochloric acid with liberation of chlorine, and at a Perhaps even one and the same organism induces both the formation and (under different circumstances) the reduction

strong heat it is reduced to protoxide, losing 66 per cent of nitric acid, and both these actions I included in the

of its weight. term “ nitrification," precisely as we consider both the

Nitrates found in Beets and in some other Roots. decomposition and the formation of carbonic acid by plants

- J. A. Barral.—The highest percentage of nitrates cal.

. A. Barra as evidences of the growth of the plant, although in

culated on the dry matter is found in the roots poorest in reality the excretion of carbonic acid is rather a sign of sugar. decay than of increase.

Inactivity of the Chrome Compounds in Com. When I stated that nitrification was not arrested by parison with Vanadium in forming Aniline-black by small quantities of chloroform I meant, and ought to have means of Aniline Salts in Presence of Chlorates.said more clearly, that chloroform is not necessarily a G. Witz.—The author, with reference to the memoir of poison to organisms allied to, or identical, with that pro. M. Grawitz (Comptes Rendus, lxxxvii., p. 844), declares ducing nitric acid.-I am, &c.,

that the salts of chrome cannot be used in place of the Orto HEHNER. salts of vanadium in their action upon aniline salts in

presence of chlorates. The presence of chrome seems

even slightly injurious. CHEMICAL NOTICES FROM FOREIGN Analysis of Crude Sugars and Saccharine Matters.

Determination of Water and of the Totality of Salts SOURCES.

with Mineral Bases and Organic Acids.-E. Laugier.

-The author determines moisture by desiccation in Note.-All degrees of temperature are Centigrade, unless otherwis hydrogen, or in coal-gas previously purified and dried. expressed.

The total mineral bases are determined by incineration in

a current of oxygen at temperatures below the melting, Comptes Rendus Hebdomadaires des Séances, l'Académie de point of chlorides. In a second portion of exa&ly double des Sciences. No. 27, December 30, 1878.

the weight the organic acids are extracted with ether ac

cording to Schlæsing's method and half the ethereal Reply to M. Berthelot.-M. Pasteur.

extract is poured to the ash obtained by the former exObservations Conncering M. Pasteur's Communi. I periment, thus re.constituting the previously existing cation.-M. Trécul.--A continuation of the controversy i salts. The mixture is again dried in the stove as in the springing out of the posthumous work of Claude Bernard. determination of water and weighed. The second half

The Microphone in Subterranean Research.-M. of the ethereal extract is then neutralised with a standard d'Abbadie.—The speaker, in presenting to the Academy alkaline liquid. From the result obtained is calculated a work by M. Michel de Rossi “ Il Microfone nella the weight of the carbonic acid equivalent to the organic Meteorologia Endogena,” remarked that the author had acids. By deducting from the weight of the salts that of successfully applied the microphone to the study of under the ash, less the weight of the carbonic acid expelled, we ground movements, and that at his observatory at Rocca 'obtain the weight of the total organic acids, and of the

CHEMICAL NEWS 54 Chemical Notices from Foreign Sources.

1 January 3i 189. water which their salts retain at the temperature adopted | Lake Nyassa, with Notes of a Recent Expediton through for desiccation.

that Country by H. B. Cotterell. March 18,"Some Remarks Innocuity of Borax Employed in the Preservation upon anOld Map of Africa contained in Janson's Atlas, pub. of Food.-E. de Cyon.-The author asserts that food

| lished at Paris in 1612," communicated and exhibited by R. thus prepared preserves all its nutritive value.

Ward. April 1, “The Contact of Civilisation and Bar.

barism in Africa, Past and Present," by Edward Hutchin. Berichte der Deutschen Chemischen Gesellschaft zu Berlin,

son, Lay Secetary of the Church Missionary Society.

Cantor Lectures-First Course, on “Mathematical InstruNo. 13, 1879.

ments,” by W. Mattieu Williams. The remaining two Action of Dehydrating Agents upon Anhydrous Acids (Fifth Memoir).-S. Gabriel and A. Michael.-The

| lectures will be delivered on the following dates:

January 20 and January 27. The second course will be authors examine the behaviour of phthalyl-propionic acid

| by Dr. W. H. Corfield, M.A., on “Household Sanitary with sulphuric acid and with sodium amalgam; of am

Arrangements.” It will consist of six lectures, to be given monia with desoxy-benzoin-carbonic acid ; and of sodium

on the following dates:- Febuary 17, 24, March 3, 10, 17, acetate with a mixture of anhydrous phthalic and iso

24. The Third course will be by W. H. Preece, on butyric acids.

“Recent Advances in Telegraphy." It will consist of five Determination of Vapour Densities.-A. W. Hoflectures, to be given on the following dates:-April 21, 28, mann.-The author has been engaged with a course of |

May 5, 12, 19. Additional Lectures-A Course of two experiments in order to ascertain the limits within which I lectures will be given by Dr. B. W. Richardson, M.A the determination of vapour densities in a barometric | L.L.D., F.R.S., on “Some Further Researches in Pulrevacuum is usefully practicable. He describes a modified factive changes," in continuation and completion of his method for the expulsion of air, but purposes giving on a course of Cantor Lectures given last session. Any future occasion a detailed account of his methods and addiitions to or alterations in the above meetings will be results,

duly announced. The Formation of Methyl-aldehyd.-A. W. Hofmann. -The author passes a mixture of the vapour of methylic alcohol and of air through a platinum tube, not too narrow,

MEETINGS FOR THE WEEK. containing a bundle of fine platinum wires. On the appli.

MONDAY, 3rd.-Medical, 8.30. cation of a gentle heat and condensing the vapours

London Institution, 5. methylic aldehyd is obtained in quantity.

Royal Institution, 5. General Monthly Meeting.
Society of Arts, '8. “Some Further Researches in

Putrefactive changes," by Dr. B. W. Richardson,
La Correspondance Sccientifique.

M.A., LL.D., F.R.S.

TUESDAY, 4tb.-Civil Engineers, 8.
December 10, 8781.

Royal Institution, 3. “Animal Development," The Patent Office at Washington has refused to grant

Prof. Schäfer. Mr. Edison a patent for his electric light, as his invention is

Zoological. 8.30. merely a reproduction of that of Mr. Starr, of Cincinnati,

Society of Arts. 8. “The Opening of the District

to the North of Lake Nyassa, with Notes of a whose patent dates from 1845. The English Patent

Recent Expedition through that Country," by H. Office is also said to have found Mr Edison's invention to

B. Cotterell. have been anticipated by that of Chanzy. of Brussels, in. | WEDNESDAY, Sth.-Society of Arts, 8. “The Best Method for Im1852 laid by him before the Academy of Sciences Febuary

proving the Condition of the Blind," by Dr. T.

R. Armitage. 25th 1858.

Geological, 8. Syrup of orgeat is made of glucose made into an emulsion

Pharmaceutical, 8. with oil and gum-tragacanth and flavoured with nitro

THURSDAY, 6th,Royal, 8.30.1

Royal Institution, 3. "Electric Induction," J. H. benzol.

Gordon. The tin-paper used for covering chocolate and other

Chemical, 8. Discussion on Dr. Tidy't Paper on esculents has been found to contain 85 per cent of lead.

the Processes for Determining the Organic

Purity of Potable Waters.

Royal Society Club, 6.30.
MISCELLANEOUS.

London Institution, 7.
FRIDAY, 7th.-Royal Institution, 9. "Bells," by Rev. H. R. Haweis.

Geologists' Association, 8. (Anniversary.)
Society for the Encouragement of Arts, Manu.

SATURDAY, 8th.-Royal Institution, 3. "Lessing," by Reginald W.

Macan factures, and Commerce, John Street, Adelphi,

Physical, 3. (Anniversary.) London, W.C. -One hundred and twenty-fifth session, 1878-79—The following arrangements have been

THE made for the forthcoming meetings of the Society:-Ordi. MONTHLY TOURNAL OF SCIENCE nary Meetings-Feb. 5, " The Best Methods for improving

AND ANNALS OF the Condition of the Blind," by Dr. T.R. Armitage. Feb. 26, BIOLOGY, ASTRONOMY, GEOLOGY, INDUSTRIAL ARTS, "Indian Pottery at the Paris Exhibition," by George

MANUFACTURES, AND TECHNOLOGY. Birdwood, M.D., C.S.I. March 5, "The Social Necessity for Popular and Practical Teaching of Sanitary Science,

Edited by WILLIAM CROOKES, F.R.S., &c. by Joseph J. Pope, M.R.C.S., L.S.A. March 12, "The Compensation of Timekeepers,” by Edward Rigg, M.A.

The first number of the Monthly Series (February, 1879) is

Now Ready. March 19, “Economical Gardens for Londoners,” by W.

Price One Shilling and Sixpence. Mattieu Williams, F.R.A.S., F.C.S. March 26,"The Treat

CONTENTS. ment of Iron to Prevent Corrosion” (a second communica.

1. "Progress"_The Alleged Distinction between Man and

Brute. tion), by Prof. Barff, M.A. In the Chemical Section

II. Matter Dead-Roger Bacon and John Dalton. January 30, “Gas Illumination," by Dr. William Wallace,

III. A Contribution to the History of Electric Lighting. By F.R.S.E. In the Indian Section-January 17, "Afghan

W. Mattieu Williams, F.C.S., F.R.A.S.

IV. The Problem of Flight-Ballooning in Arctic Exploration. istan," by C. E. D. Black, Col. H. Yule, C.B., R.E., will pre V. Electric Lighting. By Prof. W. E. Ayrton. side. January 21,"Quest and Early European Settlement of

VI. Instinct or Reason ? India," by George Birdwood, M.D., C.S.I. February 21,

VII. New Achromatic Microscope.

VIII. Safe Anästhesia. "The Trade of Central Asia, by Trelawney Saunders. IX. On the Transmission of Power by Means of Electricity. By March 7, "The Moral and Material Progress of India,"

Profs. Elihu Thomson and Edwin J. Houston. by H. Phillips. In the African Section - January 21. | Correspondence-The Band-Pattern in Animals-The Sea-Serpent. "Retrospect and Prospect in Egypt," by B. Francis Cobb.

Reviews of Scientific Works--Science Noteg-Proceedings of

Scientific Societies. February 4, "The Opening of the District to the North of!

London : 3, Horse-Shoe Court, Ludgate Hill.

CHEMICAS News, I

Transmission of Power by means of Electricity. February 7, 1879. 7

55

cable and connections between them the o'or of this unit THE CHEMICAL NEWS. Then the current which Aows will be

CERTO

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1017 1'0I 240

VOL. XXXIX. No. 1002.

If now an additional machine, A', Fig. 2, and an additional motor, B', and an additional mile of cable, be introduced into the above circuit, the electromotive force will be

doubled, and the resistances will be doubled, the current ON THE

strength remaining the same asTRANSMISSION OF POWER BY MEANS OF

I+ I
ELECTRICITY.
By Profs. ELIHU THOMSON and EDWIN J, HOUSTON.

Here it will be seen that the introduction of the two
additional machines, A' B', has permitted the length of

the cable c to be doubled, without increasing the strength The statements recently made as to the size and cost of of the current which flows, and yet allowing the expendithe cable that would be needed to convey the power of ture of double the power at A A', and a double recovery Niagara Falls to a distance of several hundred miles by at B B' of power, or, in other words, a double transmission electricity, have induced the authors to write the present of power without increase of current. Increase, now, the paper, in the hope that it may throw light upon this in number of machines at A to say one thousand, and of teresting subject.

those at B in like proportinn, and the distance between As an example of some of the statements alluded to, we them, or the length of the cable, one thousand, or in the may cite the following, viz. : That made by a certain case we have supposed, make it one thousand miles, its electrician, who asserts that the thickness of the cable diameter remaining the same. Then, although the same required to convey the current that could be produced by current will flow, yet we have a thousand times the exthe power of Niagara, would require more copper than I penditure of power at one end of the cable, and a thousandexists in the enormous deposits in the region of Lake I fold recovery at the other end, without increase of current. Superior. Another statement estimates the cost of the and the same would be true for any other proportion. cable at about 60 dols. per lineal foot.

Since the electromotive force is increased in proportion As a matter of fact, however, the thickness of the cable to the increase of power transmission, the insulation of required to convey such power is of no particular moment. the cable and machines would require to be proportionally Indeed, it is possible, should it be deemed desirable, to increased.

As an example it may be mentioned that a dynamoFig. 1,

electric machine used for the purpose of A in the figure,

may have a resistance of say 40 ohms, and produce an 1 Miles

electromotive force of say 400 volts. Such a machine might require from three to five horse-power when used in connection with a suitable motor B, for recovery of the power transmitted.

If the resistance of the motor B be, say, 60 ohms, and the cable transmitting the currents a distance of one

mile be one ohm, then the current convey the total power of Niagara, a distance of 500 miles

C=

- 400 400 or more, by a copper cable not exceeding one-halk of an inch

60+40+1 101 in thickness. This, however, is an extreme case, and the exigencies of practical working would not require such

If, now, one thousand machines and one thousand motors,

and a thousand miles of cable, each of the same relative restrictions as to size.

resistances be used, the current The following considerations will elucidate this matter. Suppose two machines connected by a cable of, say, I mile

1000 X 400 in length. One of these machines, as, for example, A,

1000 X 101 Fig. 2.

B/

2 Miles

Fig. 1, is producing current by the expenditure of power ;, which has manifestly the same value as before. If our the other machine, B, used as an ele&rical motor, is supposition of the power used to drive one machine be producing power by the current transmitted to it from A correct, then from three to five thousand horse-power by the cable C. The other terminals, x and y, are either would be expended in driving the machines, and possibly put to earth or connected by a separate conductor. about 50 per cent of this amount recovered. Then we

Let us suppose that the electromotive force of the have from 1500 to 2000 horse-power conveyed a distance current which flows is unity. Since, by the revolution of of 1000 miles. What diameter of copper cable will be B, a counter-electromotive force is produced to that of A, required for such transmission ? Since this cable is supthe ele&romotive force of the current that flows is manja posed to have the resistance of one ohm to the mile, cal. festly the difference of the two. Let the resistance of A culation would place the requisite thickness at about and B together be equal to unity, and that of the mile of 7 inch. If, however, the distance be only 500 miles, then

56

Effect of Heat on the Di-iodide of Mercury.

CHEMICAL NEW,

Feburary 7, 1879. the resistance per mile may be doubled, or the section of truncation of the edges until they disappeared, whilo the cable be decreased one-hall, or its diameter will be square-based octahedrons were produced in their place. less than the } inch.

The iodide is clearly capable of existing in two crystal. For the consumption of 1,000,000 horse-power a cable | line forms belonging to different systems, and of passing of about 3 inches in diameter would suffice under the from one form to the other, either by diminution of temsame conditions. However, by producing a much higher perature or by simple mechanical means. Such a subelectromotive force, the section of the cable could be stance would seem to be likely to possess peculiarities in proportionally reduced, until the theoretical estimates, its modes of expansion under the influence of heat. In which we have given in the first part of this paper, might order to test this the iodide was submitted to the same be fulfilled. The enormous electromotive force required experimental treatment as that employed in the case of in the above calculation would, however, necessitate such the iodide of silver, and previously described in detail. perfect insulation of the cable, that the practical limits Homogeneous rods of the iodide of mercury were might soon be reached. The amount of power required heated in paraffine in the expansion apparatus described to be conveyed in any one direction would, of course, be and figured in the previous paper, and the extent of ex. dependent upon the uses that could be found for it; and pansion due to a given range of temperature was noted. it is hardly conceivable that any one locality could ad. The apparatus was standardised by means of a rod of fine vantageously use the enormous supposed power we have homogeneous silver. The same micrometer, reading to referred to.

soboth of an inch, was employed, and the mode of con. Stripped of its theoretical cousiderations the important ducting the experiments was precisely the same as in the fact still remains, that with a cable of very limited size, case of the iodide of silver. Two slight changes were an enormous quantity of power may be transferred to made in the apparatus, however :- the one consisted in considerable distances. The burning of coal in the mines, the substitution of a massive stone base for the wooden and the conveyance of the power generated by the flow one hitherto used; and the other the replacement of the of rivers, may therefore be regarded as practicable, always, | glass rods moving in stuffing boxes by curved equal-armed however, remembering that a loss of about 50 per cent levers moving over the rim of the trough, by which means will be almost unavoidable.

the leakage of hot paraffine at the stuffing boxes was pre. It may be mentioned that Dr. C. W. Siemens and Sirvented. William Thomson have recently made statements that Bars of the iodide of mercury were cast in clean glass are in general accordance with the views here expressed. tubes, and here at the outset the experimental difficulties

commenced. For not only was it difficult to obtain a homogeneous rod, on account of the volatilisation of the

iodide at a temperature slightly exceeding its melting ON THE EFFECT OF HEAT ON THE DI IODIDE point, but the rod when cold was found to be so brittle

that it usually broke in the attempt to remove the glass OF MERCURY, Hg12.*

envelope from the outside. Eventually good rods were By G. F. RODWELL, Science Master, and H. M. ELDER, a Pupil

procured by slowly melting the iodide in thin glass tubes in Marlborough College.

and annealing in hot paraffine. When the whole was cold the glass was cut on the outside, and carefully broken off

the ends of the rod, which were sawed plane by a fine In continuation of the experiments on the effects of heat

steel saw, and then furnished with metal caps, and the on the chloride, bromide, and iodide of silver, which one

rod was placed between the levers of the expansion of us has previously had the honour of communicating to

| apparatus. After heating the bar once or twice in the Socieiy,t it was thought to be advisable to search in

paraffine to a temperature approaching its melting point some of the other metallic iodides for molecular anoma.

longitudinal rifts appeared in the glass envelope, which lies similar to those presented by the iodide of silver.

was then easily removed, leaving a clean homogeneous Among these no substance appeared more likely to

rod of the iodide. possess such anomalies than the di-iodide of mercury.

On heating a mass of the crimson amorphous iodide, This substance, as is well known, is dimorphous. In the

it turns yellow at 126° C., and just before the melting. amorphous condition it presents the appearance of a bril.

point is attained the yellow changes to a deep red-brown. liant scarlet powder, which, if heated, fuses at 200° C.,

The liquid resulting from the fusion has the appearance and volatilises just above the fusing point to a vapour more

of liquid iodide of silver, that is to say, it has the exact than twice as dense as that of mercury. The vapour con

colour of bromine. The liquid when cooled solidifics to denses to rhombic prismatic crystals, which frequently

a red-brown solid, which speedily becomes yellow, and at become scarlet while cooling, but which, if they still re

126° C. it changes to the crimson octahedral variety. main yellow when cold, instantly become scarlet if rubbed

Distinct cracking sounds, due to inter-molecular move. or otherwise mechanically agitated. According to Waring

ments, were heard during the continuance of the change. ton, this change is due to the transformation of the

Heat is absorbed when the red iodide changes to yellow, rhombic prisms into acute square-based octahedrons with

and is given out when the yellow iodide changes to the truncated summits. If the yellow prismatic crystals are

red. placed under the microscope, and are then touched, the

A bar of the iodide was placed in the expansion appa. change to the red variety may be observed to go on

ratus, melted paraffine was forced upon it, and when the through the mass of contiguous crystals, accompanied by

index had become quite steady, a gentle heat was applied a slight movement, but the external form of the crystals

to the paraffine. The index showed a regular and slow remains unchanged, consequently pseudomorphous crys

expansion until a temperature of 126° C. was reached, tals are produced; and the larger shombic prisms have

when the bar began to change from the octahedral to the been resolved into a mass of minute octahedrons. Frank.

prismatic condition, and without further rise of tempera. inheim asserts that by the application of a very gentle

iure rapid expansion took place. The temperature was heat both the red and the yellow crystals may be sub

kept constant until the change was complete, and was limed together, and he believes that the vapuur of the

then slowly raised. A regular expansion now took place yellow crystal passes off a: a lower temperature than that

under a higher coefficient than before the molecular of the red. Warington found that the precipitate pro

change, and this continued until the melting-point was duced by iodide of potassium in chloride of mercury

attained. The results were concordant. appeared under the microscope to be composed of rhom.

The expansion in passing from the solid to the liquid bic laminæ, which gradually altered their form by the

condition was determined by weighing mercury in a tube, * Paner read at the Royal Society.

and afterwards filling it to the same height with fused + Proc. Royal Society, vol. xxv., p. 230.

liodide. The specific gravity of each substance being

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