Obrazy na stronie

CELEWICAL NEWS; } Extraction of Gold, Silver, and Other Metals from Pyrites. 7

contained in the boiled and filtered water, because I waggon. The roaster is built as a muffle, with a sole of calcium sulphate is practically insoluble at a pres. brick or cast-iron plates laid at a slight incline, to facilisure of one atmosphere of steam. The calcic oxide tate the transference of the charges. At the lower end is determined in 350 c.c. of the boiled and filtered there is a depression of about 6 inches, forming a recess, water, calculated into dry sulphate, and added which extends half way over the reverberatory furnace, and on to solids deposited on boiling. The difference has an opening which can be closed with a slide, through between the number so obtained and the total solids which the contents of the recess may be at once transgives solids retaining solubility on boiling under ferred to the furnace. At the end of the roaster is an pressure, which solids are only of account in as far arsenic flue if required. Farther on is the combination as they augment the boiling-point of the residual chamber, built of sheet-lead, supported by an external water. It will of course be obvious that if framing of wood; the sole is of sheet-lead, supported on a water contains free acids, except carbonic, that iron plates over the flue. The sole is divided into eight latter part of the process will be omitted.

stages, each of which is an inch higher than the one nearer

the roaster. Beyond the combination chamber is a conI have always viewed the boiling of a water in a thin densing tower, which may be built of brick, laid in a putty glass flask as a very exceilent method of judging of its of clay and coal-tar, or, better, sheet-lead, supported by scale-forming qualities, and it is quite remarkable to note

an external framing of wood. The condenser is filled with various peculiarities of deposits so obtained.

coke or pebbles, supported on iron bars covered with lead, In reporting an analysis of boiler water made by this allowing a free space for the entry of the gases evolved in method I adopt the following tabulation :

the roaster. Surmounting the cuke is a perforated sheet Grains per gal. Pounds per 100 galls. of lead, with suitable openings for the escape of the resi. Solids deposited by boil

dual gases, which may be conducted by a pipe to a chiming under pressure

ney. On the perforated lead plate water is delivered at inSolids remaining in solu

tervals by a self-ading tumbler, kept supplied by a cistern. tion on boiling under

The water escaping through the holes in the lead plate is pressure

uniformly distributed over the coke, and trickles down.

wards, escaping over the sole of the combination chamber, Then follow remarks as to the analyst's opinion of the flowing over each stage in succession, and from the lowest water generally. I need hardly say that it is the bounden

to a wooden cooler, whence it is again pumped to the duty of every one who attempts the analysis of boiler cistern. water to make himself well acquainted with the construc- The roaster should have two or three small fireplaces at tion and manner of working the different makes of boilers intervals underneath the sole, to get it to a working heat, in ordinary use, and also to study well the reactions of which may be closed when this is attained, the flame from the various salts natural waters contain when subject to

the reverberatory furnace, mixed a sufficient quantity heat and pressure combined. When one views the evi- of air through openings in the flue, then supplying sufficient dence produced before coroners' juries dealing with cases heat, of death from boiler explosions, it is often very painfully The roaster soie being heated to a dull red heat, 2 cwts. apparent that there is a great deal yet to be done by of the dressed pyrites, or ground regulus, is mixed with chemists in the tracing of effect to cause, the information from 10 to 15 per cent of previously roasted ore, and afforded being often of the most meagre quality, and a charged into the upper end of the roaster, so that it occufield of inquiry embracing the salvation of life and pro- pies about 2 feet of the length, and spreads across the perty is surely one in which honour is not wanting. sole, which it should cover to the depth of one and a half Laboratory and Assay Office, Darlington,

inches. The ore soon becomes ignited, evolving sul. December 19, 1878.

phurous, sulphuric, and arsenious oxides. The last is condensed in the arsenic flue, and the two former pass through the combination chamber to the condensing tower, and are there absorbed by the descending water.

In an hour's time the charge is moved 2 feet to the left,

and a second charge of the mixture is placed in the space METHOD OF EXTRACTING GOLD, SILVER, AND cleared. At the end of another hour the first charge is OTHER METALS FROM PYRITES.*

moved 2 feet to the left, the second to the space cleared,

and a third is introduced, and so on, until at the end of By W. A. DIXON, F.C.S., Cor. Mem. Nat. Hist. Soc. Glasgow.

twenty-four hours the sole of the roaster is covered. The (Concluded from p. 303).

upper part of the roaster should be a: a very dull red heat,

whilst the lower should be sufficiently hot to decompose The method of treatment of the concentrated ore, or

any sulphate of iron formed. regulus, is the same whether the sulphides are rich in the charcoal-dust, or other carbonaceous matter is now spread,

On the sole of the recess from 35 to 40 lbs. of coal-dust, precious metals or not, but requires variation according and the calcined residue from the first charge is turned to-First, the presence or absence of copper ; second, the proportion of copper ; and, third, the presence or absence downwards, and a fresh charge of mixture introduced. In

over on top of it, each charge in the roaster is moved of lead.

To begin with the simplest case, viz., with pyrites free another hour a similar quantity of carbon is spread un top from copper. The apparatus required consists of–1, a

of the charge in the recess, and the second charge is roaster ; 2, a reverberatory furnace; 3, an arsenic flue, turned over on top, and so on until eight successive (if the pyrites are arsenical); 4, a leaden combination charges of roasted residue and carbon are in the recess.

The contents of the recess are then transferred to the chamber; 5, a leaden condensing tower; 6, a series of lixiviating tanks and coolers. It is best to construct the reverberatory furnace through the opening; the whole is furnace, roaster, arsenic Aue, converting chamber, and well stirred up, and spread over the sole. The furnace is tower in one line, so that the waste heat from the rever

closed, and kept at a moderate red-heat for eight hours, beratory furnace heats the sole of the roaster and con

the furnace being kept full of a smoky flame to assist reverting chamber. Thereverberatory furnace is constructed

duction. The oxides are thus reduced to the metallic in the usual manner, but the sole is made simply of brick, state, and the heat should be kept so low as to prevent the

At the end and flat, with an opening in the centre or side, through of eight hours the reduced metal is withdrawn from the which the charge may be raked out into an iron hopper furnace at the opening into the hopper waggon, which is * Read before the Royal Society of N.S.W. August 1, 1877.

immediately closed, so as to prevent access of air. The


8 Extraction of Gold, Silver, and Other Metals from Pyrites. {


January 3, 1879. furnace is again charged from the recess, which has mean- , by roasting the precipitate, extracting the copper by conwhile been filled.

denser liquor, and melting the residual silver. When the hopper is cool enough to be handled, the con- The residue in the lixiviating tanks is drained, dried, tents are rapidly transferred to a vessel containing water, mixed with one-fourth of its weight of carbon, reduced, best by placing the waggon over the vessel and withdrawing and otherwise treated as above described, to obtain the a slide in its bottom, so as at once to thoroughly wet and gold and remaining silver. cool the contents.

The crystals of sulphates of copper and iron in the One eighth part, or thereabouts, of the cooled metal is coolers are removed from time to time, drained and dried. now placed in the upper stage of the combination chamber, One ton of the dried crystals is charged into the muffle over which water from the condenser, charged with sul furnace, and there exposed to a fully cherry-red heat, so phurous and sulphuric acids, is flowing. In one hour the

as to convert the whole of the sulphates into oxides. The charge is moved to the second stage, and a second charge sulphurous and sulphuric acids evolved are conveyed to is introduced, and so on, until in eight hours the chamber the condensing tower, which is supplied with sulphate of is filled, and that furnace charge exhausted. The metal copper solution from the coolers, slightly diluted with the is rapidly acted on by the acids, and converted into sul weaker wash liquor by which the acids are condensed, phate, sulphite, and hyposulphite of iron; but by the com. and used for extracting roasted ore.

When vapours are bined action of the air and water, assisted by the heat from

no longer evolved the calcined residue is removed from the fue, the first largely predominates. The charge on the muffle. A similar charge of dried sulphate is heated the lowest stage is now removed, and may be at once in the mufle furnace to a dull red, so as to convert the lixiviated with water ; but it is best to keep it for a few sulphate of iron into oxide, and when fumes are no longer days in a moist state, to finish the conversion into sul evolved the charge is raked out, mixed with 27 cwts. of phate. It is then lixiviated with water, which removes

coal or charcoal dust, and charged into the reverberatory sulphate of iron (also zinc, nickel, and cobalt is present), furnace, where it is melted, when sulphurous and other and leaves a residue containing the gold and silver, mixed gases are evolved, causing the mass to boil. When boil. with quartz, excess of carbon, and free sulphur. The ing ceases the oxides are added to the charge, and the carbon and sulphur are then burned off, and the gold and melting heat continued until the whole is in a tranquil silver separated from the quartz by washing, amalgamating, fusion, when the slags are raked off and the rough copper or otherwise. If the extraction of the sulphate of iron is

run into moulds. effected with boiling water, and the liquor run into coolers,

If the ore contains lead it is found in the residue conthat salt may be obtained in a marketable condition; or, taining the gold and silver; and is present in sufficient the crystals being calcined at a dull-red heat, yield a fine quantity the residue may be smelted, and the gold and red oxide of iron suitable for painting, and sulphuric acid, silver recovered by cupellation. which may be condensed.

If not present in sufficient quantity to smelt, but still so If the ores contain copper in small proportion only, the much as to interfere with the amalgamation, the residue roasting, reduction, and solution of the iron are conducted is roasted, treated with a little condenser liquor, washed, precisely as above described, using, however, as little and the lead extracted with solution of caustic soda, caroon as possible for the reduction, so as to obtain the solution of lead in caustic soda is mixed with sawdust or

when the gold and silver may be amalgamated. The residue nearly free therefrom. The copper is then found in the residue principally as sulphide. This residue is carbon, evaporated to dryness, heated strongly, and the roasted at a dull red heat, and the copper is extracted by rendered caustic by lime, when the lead remains as an

carbonate of soda dissolved out with water, and again treatment with condenser liquor and crystallisation, as

insoluble residue mixed with carbon. described below, the gold and silver being obtained from the residue as before.

The advantages of this mode of treatment are that the

sulphides are entirely got rid of, whilst if through inatten. Ores or sulphides containing much copper are roasted tion in the roasting some sulphides remain, only the at a dull red heat, the inixing with roasted ore, roasting, small proportion that has escaped requires to be re-roasted, and condensation of the gases being conducted as before. instead of the whole mass of ore as is usually the case. The well-roasted ore is withdrawn from the furnace and in the extradion of copper from the sulphides the whole cooled. The cooled residue is then shaken into a lixiviat-1 of the copper may be obtained in the form of crystals, ing tank partly filled with a solution of sulphate of copper, from which the copper may be recovered without evaporacontaining sulphuric acid and sulphurous acid, obtained tion of liquors; and in the whole of the operations, with as below described ; the mixture is allowed to digest, and the exception of smelting for copper, the temperature3 treated with successive portions of the solid solution until are so low that the cheapest materials may be used for the escaping liquor contains free sulphuric acid. The lixi. the construction of furnaces. The temperature being low, viation is then carried on with a cold saturated solution, the loss of silver by volatilisation is reduced to a minimum, of sulphate of copper from the coolers, which is made whilst there is absolutely no loss of gold, except through boiling hot in a leaden or copper boiler, until the specific the careless spilling of the material. Lastly, as neither gravity of the entering and escaping solutions is the same. salt, iron, or other material is consumed in the process, a The whole of the copper liquors are run into wooden large source of expense in all previous wet methods of coolers, where crystals of the sulphates of copper and treatment is avoided; and the process is adapted for use iron are deposited. When the lixiviation has been carried wherever the ores are found. as far as possible with the copper solution, it is drawn from the tank until it stands only an inch or so above the solid contents, and 12 inches of water are carefully floated on top, and the drawing off the copper solution continued PROCEEDINGS OF SOCIETIES. from below until the water is only an inch above the solid contents, when a second wash is run on, and in the same manner a third if necessary. The copper liquors are run MANCHESTER LITERARY AND PHILOSOPHICAL to the coolers as long as they mark above 20° of Twaddel,

SOCIETY. below that strength ihey are run to a separate tank to be

Ordinary Meeting, November 26, 1878. used for the first wash of another lot.

If the ore contains silver, a little is found in solution in J. P. JOULE, D.C.L., LL.D., F.R.S., &c., President, in the copper liquor, and is separated therefrom by filtering

the Chair. it through a bed or beds of cement copper, or, better, of precipitated sulphide of copper, before running the liquor "On some improved Methods of Producing and Regula to the coolers. "The silver is recovered from time to time lating Electric Light," Part II., by Henry Wilde.

January 3, 1879.
} Chemical Notices from Foreign Sources.

9 In a former communication to the Society I directed duced. When the circuit is interrupted the armature is attention to the fact that when the electric light is pro- released ; the upper ends of the carbons come into con; duced from the ends of two carbon pencils placed parallel tact, and the light is produced as before. When several to each other, if the strength of the electric current, the pairs of carbons are placed in the same circuit they are, thickness of the carbons, and the distance between them by this arrangement, lighted simultaneously. are rightly proportioned, the carbons will burn steadily downwards until they are wholly consumed, without any insulating material between them. To initiate the light by this method it is necessary to complete the electric CHEMICAL NOTICES FROM FOREIGN circuit between the carbons by means of some conducting substance, which volatilises on the passage of the current,

SOURCES. and establishes the electric arc between the points.

When a number of such lights are produced simulta- Note.-All degrees of temperature are Ceatigrade, unless otherwise neously from the same source of electricity, any interrup- expressed. tion in the continuity of the current extinguishes all the lights in the same circuit, and each pair of carbons re- Comptes Rendus Hebdomadaires des Séances, l'Académie de quires to be re.primed before the lights can again be

des Sciences. No. 24, December 9, 1878. established. This defect, as will be obvious, would cause great inconvenience when the lights are not easily acces

Report on Mr. Lawrence Smith's Memoir on the sible, or are at considerable distances apart.

Native Iron of Greenland and the Dolerite which it In the course of my experiments it was observed that contains.-MM. Ste-Claire Deville, Des Cloizeau, and when the electric circuit was completed at the bottom of Daubrée.—Mr. Smith concludes that all the native irons a pair of carbons close to the holders, the arc immediately of Greenland are mutually similar, and, on the contrary, ascended to the points, where it remained so long as the that they differ from the meteoritic irons. The former current was transmitted. My first impression of this

are confined to the basaltic region, extending from lat. peculiar action of the arc was, that it was due to the 699 N. to 76° N., and are most abundant in its best ascending current of hot air by which it was surrounded. developed regions. It is known that the terrestrial rocks This, however, was found not to be the cause, as the arc

which offer a resemblance to meteorites all belong to the travelled towards the points in whatever position the deeper regions of the earth's crust. In those regions of carbons were placed, whether horizontally or vertically in Greenland where native iron occurs layers of lignites an inverted position. Moreover, when a pair of carbons underlie here and there the great basaltic deposit, and it were held in the middle of the holders, the arc travelled is possible that these carbonaceous matters may have

Still it upwards or downwards towards the points, according as partially reduced the iron to the metallic state. the circuit was established above or below the holders. is equally possible that the native iron may have been The action was in fact recognised to be the same as that brought up from below, like the native alloy of platinum which determines the propagation of an electric current

and iron which is found embedded in peridotic rocks. through two rectilinear and parallel conductors submerged

Automatic Current-Regulator.-M. Hospitalier.-By in contact with the terrestrial bed, which was described means of the author's apparatus the intensity of a current by me in the Philosophical Magazine, August, 1868. may be maintained between two limits fixed beforehand,

In all the arrangements in general use for regulating and which may be as near together as is desired. the electric light, the carbon pencils are placed in the Note on a Remarkable Specimen of Iron Silicide. same straight line, and end to end. When the light is -J. Lawrence Smith.-The specimen has the appearance required, the ends are brought into momentary contact, of an ingot from the blast-furnace and has a brilliant and are then separated a short distance to enable the arc surface. It resists nearly all reagents except hydrofluoric to form between them. The peculiar behaviour of the acid and caustic alkalies at a red heat. It contains 15 per electric arc when the carbons are placed parallel to each cent of silicium, whilst the alloy of iron and manganese other suggested to me the means of lighting the carbons richest in silicium has only 10 per cent. Its origin is automatically, notwithstanding the fact that they could unknown. only be made to approach each other by a motion laterally, and to come into contact at their adjacent sides.

A New Acid Derived from Camphor.-A. Haller. To

-The author has obtained a homologue of camphoric accomplish this object one of the carbon holders is acid, which he proposes to name hydroxy.campho-car, articulated or hinged to a small base plate of cast-iron, bonic acid, C,H180g It decomposes the alkaline and which is so consiruded as to become an electro-magnet alkaline earthy carbonates, forming salts with their bases. when coiled with a few turns of insulated wire: The The author has analysed the salts of lead, copper, and carbon holder is made in the form of a right-angled lever,

zinc. to the short horizontal limb of which is fixed an armature placed over the poles of the electro-magnet. When the

Formation of Hexamethyl-benzin by the Decom. movable and fixed carbon holders are brought into juxta position of Aceton.-W. H. Greene.-The author has position, and the carbons inserted in them, the upper parts obtained this product in quantity by the action of aceton of the two carbons are always in contact when no current upon melted chloride of zinc at a high temperature. is transmitted through them.

Normal Ethyl-oxy-butyric Acid and its Derivatives. The contact between the carbons is maintained by .-M. Duvillier.--An examination of the ethyl-oxymeans of an antagonistic spring inserted in a recess in butyrate of methyl and of ethyl-ox;-butyramide. one of the poles of the electro-magnet, and reacting on Presence of Ytterbium in the Sipylite of Amherst the under side of the armature. One extremity of the (Virginia).-Marc Delafontaine. The author has isolated coil of the ele&ro.magnet is in metallic connection with irom this mineral a base whose characters agree closely the base of the carbon holder, while the other extremity with those of M. Marignac's ytterbia. of the coil is in connection with the terminal screw at the

Existence of Baryta and Strontia in all the Rocks base of the instrument, from which it is insulated. The forming Primordial Districts.-M. Dieulafait:- The coils of the electro-magnet are thus placed in the same circuit as the carbon pencils.

author finds that these earths are easily recognised in When the alternating current from an electro-magnetic felspars, in the mica of primitive rocks, in granites coarse induction machine is transmitted through the carbons, rocks are the original source of baryta and strontia.

or fine, and in syenite. The author considers that these the electro-magnet attracts the armature and separates the upper ends of the carbons, which brings them into

Danger of the Use of Borax for the Preservation their normal position, and the light is immediately pro- of Food, and Causes why certain Substances Deprive


" Auditional Note on Pen

CHEMICAL NEWS, to Chemical Notices from Foreign Sources.

January 3, 1879. Meat of its Nutritive Properties.-G. Le Bon.--Meat bigin. Botany.--(Medal) Mr. Lord; (Certificate) Mr. steeped in a solution of pure borax, or covered with the Scammell. Materia Medica.—(Medal) Mr. Newbigin ; powdered salt, may be preserved unchanged for a long time, (Certificates) Mr. Lemmon and Mr. Harrison, equal. but is taken as food such meat produces intestinal Practical Pharmacy and Dispensing.- (Medal) Mr. derangements, which necessitates its disuse. Borax, | Lemmon; (Certificate) Mr. Lord. Silver Medal of the taken in small successive doses, is a poisonous agent, the School, for Session 1877-78.-Mr. John E. Phillips. use of which in the preservation of alimentary substances ought to be strictly prohibited. M. Peligot has already

NOTES AND QUERIES. pointed out the poisonous action of horax upon plants. Several compagnies in America, who had begun to use As halte Pitch.--Will any of your correspondents kindly give me this salt for the preservation of meat, have been obliged any information of the best method of making asphalte

pitch, and the to give it up. The author further shows the necessity of Peroxide of Hydrogen.-Will'any of your readers inform me how avoiding saline substances altogether for the preservation I can obtain information how to make peroxide of hydrogen of ten of food, an object which he considers attainable solely by Wardle.

volumes strength ? I want it for commercial purposes.-THOMAS the use of cold.

Distillation of Tar.-(Reply to R. J.)-The best work on the distillation of tar, &c., is by Dr. George Lunge, published by Vieweg


MEETINGS FOR THE WEEK. University of London.-The following are lists of Monday, Jan. 6th.-Medical, 8. the candidates who have passed the recent examinations: TUESDAY, 7th.— Mineralogical, at 116, Victoria Street, 8.

London Institution, 5.

"On Pilo. --Second B.A. and Second B.Sc. Examinations.-Exami.

lite, an unrecognised species," by Prof. M. F. nations for Honours (B.A. and B.Sc. conjointly).-Mathe

Heddle. "On so-called Green Garnets from the matics. First Class : J. Larmor, B.S:. (Scholarship), St.

Urals," by Prof. A. H. Church. "On the Magne

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withite," by J. H. Collins, F.G.S.

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THE J. W. Greig (Prize) University College ; O. E. Boding. QUARTERLY JOURNAL OF SCIENCE. ton, Giggleswick School and private tuition; F. J. Mor. rish, Cheshunt College and private study. Second Class :

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Now ready, No. LXI., January, 1879, price 58.
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CONTENTS. Galton, Stonyhurst; J. T. Christie, King's College, Lon- 1. On the Thickness of the Antarctic Ice, and its Relations to don, and Exeter, Oxford. Chemistry (B.Sc. only). R.

that of the Glacial Epoch. By James Croll, LL.D., F.R..

II. Gravitation as a Facor in the Organic World. By William Gill, St. Bartholemew's Hospital; C. F. Cross, King's

Crookes, F.R.S. and Owens Colleges. Experimental Physics. Second III. Sanitary Science in the United States : Its Present and its Glass : L. II. Edmunds, University College. Third Class :

Future. By Albert R. Leeds, Ph.D. M. F. O'Reilly, St. Joseph's College, Clapham; G. W.

The Course of Nature. By Prof. Simon Newcomb.

V. Peruvian Antiquites. By E. R. Heath, M.D. von Tunzelmann, University College. Physical Geography

Notices of Scicntific Works, Obituary, &c.
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The JOURNAL OF Science will in future be issued MONTHLY
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Annual Dinner took place at the Horns Assembly Rooms semeral appearance remaining the same.
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The first of the Monthly issue will appear on

FEBRUARY ist, 1879. new students present, together with a large number of

Price ONE SHILLING and SIXPENCE. gentlemen interested in the progress of the School. Dr.

In addition to the usual articles on subjects of present scientific Julius Pollock presented the prizes to the following suc. interest and reviews of scientific works, the MONTHLY JOURNAL OF cessful students :- Senior Chemistry. - (Medal) Mr. SCIENCE will contain abstracts of papers read before the Scientific Pocock; (Certificate) Miss Stammwitz. Junior Che

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London 'se-Shoe Court, Ludgate Hill, E.C.


Nature of the Elements.


the spectra of the brighter stars before this point could THE CHEMICAL NEWS. be determined.

I also remarked that this result enabled us to fix with

very considerable accuracy the electric dissociating conVOL. XXXIX. No. 998.

ditions which are equivalent to that degree of dissociation at present at work in the sun.

in Fig. 3 I have collected several spectra copied from

photographs in order that the line of argument may be DISCUSSION OF THE WORKING HYPOTHESIS


First we see what happens to the non-dissociated and ELEMENTS ARE COMPOUND BODIES.

the dissociated chloride. Next we have the lines with a

weak voltaic arc, the single line to the right (W. L.4226°3) By J. NORMAN LOCKYER, F.R.S.

is much thicker than the two lines (W. L. 3933 and 3968) (Concluded from p. 5.)

to the left, and reverses itself.

We have next calcium exposed to a current of higher

tension. It will be seen that here the three lines are II.

almost equally thick, and all reverse themselves. Application of the above Views to Calcium, Iron, Lithium, Now it will be recollected, that in the case of known and Hydrogen.

compounds the band structure of the true compounds is

reduced as dissociation works its way, and the spectrum Calcium.

of each constituent element makes its appearance. If in It was in a communication to the Royal Society made 3 we take the wide liae as representing the banded specnow some time ago (Proc., vol. xxii., p. 380, 1874), that I trum of the compound, and the thinner ones as representfirst referred to the possibility that the well-known line ing the longest elemental lines making their appearance spectra of the elementary bodics might not result from as the result of partial dissociation, we have, by hypothethe vibration of similar molecules. I was led to make the sis, an element behaving like a compound.

Fig. 3.—THE BLUE END OF THE SPECTRUM or Calcium Under Different CONDITIONS.


1. Calcium is combined with chlorine (Caci,). When the temperature is low, the compound molecule vibrates as a whole, the spectrum is

at the red end, and no lines of calcium are seen. 2. The line of the metal seen when the compoun' molecule is dissociated to a slight extent with an induced current. 3. The spectrum of metallic calcium in the electric arc with a small number of cells. 4. The same when the number of cells is increased. 5. The spectrum when a coil and small jar are employed. 6. The spearum

when a large coil and large jar are used. 7. The absorption of the calcium vapour in the sun. remark in consequence of the differences to which I have If the hypothesis be true, we ought to be able not only already drawn attention in the spectra of certain elements to obtain, with lower temperatures, a still greater preas observed in the spectrum of the sun and in those ob- ponderance of the single line, as we do; but with higher tained with the ordinary instrumental appliances.

temperatures, a still greater preponderance of the double Later (Proc. Roy. Soc., No. 168, 1876) I produced evi- ones, as we do. dence that the molecular grouping of calcium which, with I tested this in the following manner :-Employing a small induction-coil and small jar, gives a spectrum photography, because the visibility of the more reiran. with its chief line in the blue, is nearly broken up in gible lines is small, and because a permanent record of an the sun, and quite broken up in the discharge from a experiment, free as it must be from all bias, is a very prelarge coil and jar, into another or others with lines in the cious thing. violet.

Induced currents of ele&ricity were employed in order I said " another," or "others,” because I was not then that all the photographic results might be comparable. able to determine whether the last-named lines proceeded To represent the lowest temperature I used a small from the same or different molecules; and I added that it induction coil and a Leyden jar only just large enough to was possible we might have to wait for photographs of secure the requisite amount of photographic effect. To

represent the highest, I used the largest coil and jar at + Paper read at the Royal Society, December 12, 1878. my disposal. The spark was then taken between two alu.

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