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closing a small hole in the observing tube by a plate of aluminium vations refer to the 4th trimestre of 1892, and are given here 0'003 mm. thick, it was possible to study their .properties out

somewhat in detail. Taking prominences first, the numbers side the tube. It was found that the rays produce a slight

show a great falling off when compared with the preceding

three months ; thus for the northern and southern hemispheres luminosity in air, and when they fall on phosphorescent bodies,

the frequency of these phenomena for the three months was held near the window, cause the latter to shine with the same 81, 78, 61 for the former (sum 220) and 105, 138, 90, for the light they show when enclosed within the vacuum tube itself. latter (sum 333) the foregoing trimestregiving 431 and 493 for each The brightness diminishes rapidly as the distance from the

hemisphere. The greatest frequencies took place in latitudes

+ 60° + 70°N. and – 30° - 40° S., but the numbers indicate window increases, so that in air all glow ceases at about 6 cm.

really two other maxima for each hemisphere, and they lie in On bringing a magnet near the tube so that the kathode rays

the zones + 30° + 20° and - 50° - 60°. Do longer fall on the inner surface of the window, all phosphor. The frequency of groups of saculæ recorded for both north and escence ceases without the tube. A quartz plate half a milli | south latitudes are given as 100 and 132 respectively ; the metre thick entirely stopped the rays; ordinary gold, copper,

average for each month amounted to 37, but for the southern

zones during October an increase to 20 above this average was and aluminium leaf, however, allowed them to pass almost un

noted ; the greatest frequencies occurred in zones + 10° + 20° diminished. In air at the ordinary pressure these rays are not and - 20° - 30°. In dealing with the spots their frequency propagated in straight lines but are diffused, so that it is im. | may be generally stated to be about half that of the faculæ. possible to obtain a sharp shadow of a body placed between the The table gives 46 and 58 for the two zones, and in this case window and the phosphorescent substance. As these waves

| also the greatest disturbances seem to have occurred in the

southern hemisphere during October ; the numbers for the cannot be generated in a high vacuum it has been up to now

monthly records are, for the northern zones 18, 13 and 15, and impossible to say whether they are only propagated when matter for the southern 26, 12, and 20, the greatest frequencies occuris present. ' By enclosing the observing tube in another, the ing in latitudes + 10° + 20°N. and - 20° - 30 S. author has shown that in the best vacuum attainable with a Prof. Tacchini, in addition to the above communication, demercury pump, these waves are transmitted with as great facility

scribes in a short note a large protuberance observed on No.

vember 20 of last year, and gives 10 figures to illustrate the as in air at the pressures ordinarily existing within Geissier

various forms which it successively assumed. The height and tubes. Different gases transmit the rays to very different ex. velocity of ascent can be gathered from the few numbers tents, thus, with hydrogen at atmospheric pressure, phosphor below : escence is produced in a body placed at a distance of 20 cm.

H. M. from the window. These experiments seem to show that while

146'3 about 10 57 for light of the smallest known wave-length the matter behaves

155'5 , II 22:5

1888 , I 21 as if it completely filled the space it appears to occupy, in the

184'I » 1 58 case of these kathode rays even gases behave as non-homogeneous

1864 2 38 media, and each separate molecule acts as an obstacle diffusing

1546 , 252 the rays.

PARALLAXES OF U AND O CASSIOPEIA.-In No. 5 of the Notes from the Marine Biological Station, Plymouth :- contributions from the Observatory of Columbia College, New Recent captures include the Polyclada Eurylepta cornuta,

York, Mr. Harold Jacoby presents us with the results he has Cycloporus papillosus and Leptoplana, the Actinian Zoanthus

obtained with regard to the parallaxes of u and o Cassiopeiæ,

as deduced by him from an examination of the Rutherfurd Couchii, and the Opisthobranchs Scaphander lignarius and

photographic measures of the stars surrounding u Cassiopeia. Egirus punctilucens. The sea has lately become increasingly

The negatives, which were twenty-eight in number, two impresricher in diatoms and floating algæ, esp. Coscinodiscus, Rhisose sions being on each plate, were made between July, 1870, and lenia and the so-called “gelatinous alga.” In the floating December, 1873, and as they were specially taken for parallax fauna the Dinoflagellate Ceratium tripos has been constantly

determinations, the observations were restricted to the months

of July, January, and December. The study of the parallax plentiful throughout the winter ; Noctiluca is very scarce. Of

here made is based upon measures of distance only. Each pair of the Hydroid medusæ, small Obelia are still abundant ; medusæ

stars was selected so as to differ approximately 180° in position of Clytia Johnstoni are generally present ; and Forbes's Thau. angle with respect to H Cassiopeiæ, and the scale value was mantias octona has been again observed. The Actinian larva determined for each pair, on each plate, in order to make the sum Arachnactis occurs in most townettings. Zoææ of Porcellana

of the distances from u constant. By taking the difference of

the same distances as the quantity from the variation of which have slightly increased in number. The Actinian Bunodes

the parallax should appear, “the excess of the parallax of the verrucosa (= gemmacea) is now breeding.

principal star over the mean of the parallaxes of the two comThe additions to the Zoological Society's Gardens during the

parison stars” is, satisfying certain conditions, finally obtained. past week include a Leopard (Felis pardus) from India, pre

The values for the parallaxes which he has obtained aresented by Admiral W. B. Kennedy, R.N., F.Z.S. ; a Common

Parallax of u Cassiopeiæ .. 0275 0'024 Squirrel (Sciurus vulgaris) British, presented by Miss Edith

u no " ... 0'232 + 0.067 Mackenzie ; two Black Rats (Mus raltus) Britisb, presented by

On comparing the former of these values with the work of Mr. Sydney Wedlock; a Panama Amazon (Chrysotis pana

other observatories the discordances, he says, are large. The mensis) from Panama, presented by Mrs. Mackey ; a European Oxford photographic result was o"'036 + 0.018, while the Pond Tortoise (Emys europaa) European, presented by Mast. ! Rutherfurd plates gave o' 249 to".045, the same pair of comJ. F. Harben ; a Macaque Monkey (Macacus cynomolgus) from parison stars being used in each case. Struve from distant India, deposited ; a Common Pintail (Dafila acuta) European,

measures deduced the value o"-251 0075, and from position

angles the value o”:425 + 0".072. “It is therefore plain that a Bell's Cinixys (Cinixys belliana), a Home's Cinixys (Cinixys

the photographic method of determining parallaxes cannot be homeana) from West Africa, purchased ; a Mute Swan (Cygnus regarded as free from systematic error." olor) European, received in exchange; three Coypus (Myopo.

FALL OF A METEORITE.--A brief account of the fall of a tamus coypus) born in the Gardens.

meteorite at a place in South Dakota, 4 km. south of Bach, on August 29 of last year, is given in the current number of

Prometheus, No. 183. It was observed about four o'clock in OUR ASTRONOMICAL COLUMN.

the afternoon, attention being first drawn to it by the sound of SOLAR OBSERVATIONS AT ROME.-In the Memorie degli a series of explosions. As the observer looked upwards he saw Spettroscopisti Italiani for March, Prof Tacchini communicates a meteoritic stone flying through the air, leaving a trail of the solar observations made at the Royal College. These obser- smoke behind it. On reaching the ground it plunged to a depth

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of 40 cm., and was so hot that the observer was unable to put SOME recent measurements in Russia, noticed by M. Venukofi his hand on it. At the explosion of the meteor several small in the last number of the Comptes Rendus are valuable as lead. portions weighing from 30-60 gr. were scattered, while the ing to some conclusions regarding the form of the geoid. weight of the chief mass amounted to 22 kg The description of | Determinations of the value of the degree of longitude along the the exterior says that it showed the general, smooth, black crust, parallels of 47° 30' and 52° accord closely with Bessel's geoid while from the fracture it was noticed to be finely granulated ; (polar flattening 3) and are widely divergent from Clarke's one could also see easily small particles of iron, which could result of zs. without any difficulty be separated by pulverisation. Chemical analysis showed that nickel and cobalt was present in considerable quantities.

THE AMIDE AND IMIDE OF SULPHURIC JAHRBUCH DER ASTRONOMIE UND GEOPHYSIK, — This

ACID. volume, which is edited by Dr. Hermann J. Klein, contains a very interesting account and summary of the work done in

FURTHER details concerning these interesting substances various branches of astronomical science during the past year.

are communicated by Dr. Traube of the laboratory of the Dunér's, Deslandres', Hale's, and Young's sun observations

Berlin University to the current number of the Berichte It has are referred to, while several other references to solar work are

long been surmised that an amide of sulphuric acid was capable given. The numerous observations made with reference to the

of existence, and Regnault assumed that the product which be major and minor planets are here all brought together ; Trou.

obtained by leading ammonia gas into a solution of sulpburyl veloi's Venus observations, the opposition of Mars, and the

dichloride in ethylene chloride consisted of that substance recent discovery of Jupiter's fifth satellite heing rather prom.

mixed with sal-ammoniac. Dr. Traube has further iovestigated inent. Under ine heading of “The Moon” Wernik's enlarge

ibe reaction and has at length isolated not only sulphuryl dia. menis, Boddiker's and Hartmann's researches and are referred

mide, SO,(NH.), but also sulphuryl imide, SONH, the imide to at some length. Comets, meteorites, and shooting stars also

of sulphuric acid, and has, moreover, prepared several metallic come in for a good share, and under the fixed stars, in which are

derivatives of each. included all variables, nebulæ, &c., are included references to the

Sulphuryl Diamide. Nova in Auriga, stellar spectroscopic observations, motion in line of sight, &c.

The most advantageous mode of preparing sulphuryl diamide

consists in saturating a solution of sulphuryl dichloride, So,cl, in THE OBSERVATORY.--From the cover of the Observatory one chloroform with ammonia. It is necessary to dilute the sulpburyi quite misses the familiar name of Dr. Common, in place of dichloride with 15-20 times its volume of chloroform, and to which are now inserted Messrs. T. Lewis and H. P. Hollis. || maintain a low temperature by extraneous cooling in order that In an editorial notice Mr. Turner says a few words to account the reaction may be under complete control, and the amm nia for this perturbation, mentioning that it is owing to pressure of gas must be carefully dried before being allowed to bubble work, which has made it impossible for either of them to con- through the liquid. The main reaction occurs in accordance duct the magazine. He concludes by saying, “ It would be with with the following equation : the keenest satisfaction that we should return to the manage. ment of the magazine if the future should have that in store for

SO,C1, + 4NH; = 2NH,CI + SO, NH.), The products are gradually deposited in the form of a white solid, which, after the completion of the reaction, is agitated with water until the whole of it is dissolved. The ammoniacal

aqueous solution is then separated from the chloroform, acidified GEOGRAPHICAL NOTES.

with nitric acid, and the whole of the chlorine removed by the The Scottish Geographical Magazine for April contains a

addition of silver nitrate. After removal of the silver chloride paper of some value by Colonel Justin C. Ross on irrigation

by filtration the acid solution is neutralised with alkali and and agriculture in Egypt, giving the result of his experience as

silver nitrate again added, when a crystalline precipitate is obDirector-General of Irrigation in that country. In consequence

tained consisting of a silver derivative of sulphuryl diamide, of the indisposition of Colonel Bailey the Magasine is now

SO,(NHAg),, together with another silver compound, whose edited by Mr. W. A. Taylor, Librarian to the Royal Scottish

composition has not yet been definitely ascertained. In order Geographical Society, who has for several years had charge of

to isolate the silver compound of sulphuryl diamide, the washed the book reviews and geographical notes.

precipitate is decomposed with the calculated quantity of hydro

chloric acid, and the resulting acid liquid carefully neutralised The April number of the Deutsche R'undschau für Geographie with ammonia ; upon now adding silver nitrate only the silver contains a coloured map of the density of population in Holland compound of unknown and complex composition is deposited. which illustrates in a manner very rare in continental map-work The pure silver compound of sulphuryl diamide is finally de an ignorance of the first principles of map colouring. The objects posiled upon adding a further quantity of silver nitrate and of map-colouring are two--one is to indicate the areas occupied sufficient ammonia to render the liquid strongly alkaline. by discontinuous and uplike conditions, such as countries, races of When the precipitated silver compound of sulphuryl diamide people, or geological formations. For this the colours have to be is decomposed wiih hydrochloric acid a feebly' acid liquid is as strongly contrasted as possible and the map is necessarily and obtained, which, when evaporated to a syrup in vacuo, at a properly a patchwork. The other object is to show the dis temperature not exceeding 40°, and afterwards allowed to stand iribution of a continuously varying quantity, like altitude, in vacuo over oil of vitriol, gradually deposits large colourless lemperature, or rainfall, and in order to attain it the colours crystals of pure sulphuryl diamide, SÓ,(NH,l. ought to merge one into the other so that the eye is carried Sulphuryl diamide is an extremely deliquescent substance from the lowest to the highest value by just perceptible grada: The crystals are rapidly dissolved by water, but are practically tions. The Austrian map referred to applies the first method insoluble in organic solvents. They sosten at 75o and melt at to bring out the second result, each different density of popula. 81. As the liquid cools, however, it exhibits the property of lion being coloured so as to contrast with the others, and io show supersusion to a very marked extent, remaining liquid many no defoile gradation from less to greater.

degrees below its melting point. The moment, however, it is Globus states that the Russian Government, dissatisfied with

disturbed by contact with a sharp body, it instantly solidifies the foreign sound of the names Dorpat and Dünaburg, have

When heated above its melting point sulphuryl diamide losos resolved to rename those towns Jurjew and Dwinsk respec.

| ammonia even below 100°; up to 250° no further decomposilively.

rion than the loss of ammonia occurs, the residual compound

being the sulphuryl imide to be presently described. Above The Paris Geographical Society held a special meeting in 250° complete decomposition ensues with the evolution of acid commemoration of the discoveries of Columbus on March 4, sumes. the four bundredth anniversary of his return from the first trans The aqueous solution of sulphuryl diamide reacts neutral lo atlantic voyage. A masterly address by M. Levasseur on the litmus and possesses a bitter laste. It yields no precipitates in moral and material consequences of the discovery of America, acid solutions either with salts of barium or platinic chloride. and a paper by Dr. Hainy on the traces of Columbus in Spain On long boiling with acids, however, it is gradually converted and Italy were the principal features of the meeting,

into sulphuric acid and ammonia, and then yields the nasual precipitates for those substances with barium or platinic verted by rapidly heating it to its melting-point over a small chloride. Its behaviour with nitrous acid is interesting. Upon gas flame. adding to an acid solution of sulphuryl diamide a few drops of Acicular crystals of a hydrated barium salt, (SO,N), Ba.2H,O, the solution of a nitrite nitrogen is at once evolved, in the have been obtained by saturating a solution of the imide with cold, and sulphuric acid is formed.

barium carbonate and afterwards adding alcohol ; also needles Sulphuryl diamide does not combine with acids. Alkalies of a lead salt and a green amorphous copper salt. appear to be only capable of removing one amido group, con The acid character of sulphuryl imide, so different from the verting the diamide into sulphaminic acid, SO,(NH) (OH). neutral nature of sulphuryl diamide, is thus seen to be quite As described in the course of the preparation of sulphuryl conclusively established.

A. E. Tutron. diamide, ammonia precipitates from a solution mixed with silver nitrate a silver compound. If the precipitate is allowed to remain in contact wiih the excess of the reagents for some time, it invariably yields numbers upon analysis which agree with THE DENSITIES OF THE PRINCIPAL The formula SO,(NHAg), If, however, it is at once separated,

GASES. it is found to consist of a mixture of this salt with the salt SO,(NH,) (NHAg).

IN former communications (“Roy. Soc. Proc.,” February, These silver compounds of sulphuryl diamide are amorphous, 1 1888; February, 1892) I have described the arrangements even after deposition from solution in hot water. When dry by which I determined the ratio of densities of oxygen and they are white powders very slightly sensitive to light. Upon hydrogen (15.882). For the purpose of that work it was not heating to 200° they decompose with evolution of sulphur necessary to know with precision the actual volume of gas dioxide.

weighed, nor even the pressure at which the containing vessel Sulphuryl diamide likewise forms a compound with mercuric was filled. But I was desirous before leaving the subject of oxide when its solution is mixed with one of mercuric nitrate. ascertaining not merely the relative, but also the absolute, The composition of this precipitale, however, appears to vary densities of the more important gases--that is, of comparing with the degree of conceniration of the solutions employed, and their weights with that of an equal volume of water : if chlorides are present a precipiiate is only obtained with a To effect this it was necessary to weigh the globe used very large excess of mercuric nitrate. Mercuric chloride pro. to contain the gases when charged with waier, an operation duces no precipitate at all.

not quite so simple as at first sight it appears. And, further, A somewhat similar lead compound is also formed when lead in the corresponding work upon the gases, a precise absolute acetate is added to a moderately concentrated solution of specification is required of the temperature and pressure at which sulphuryl diamide.

a filling takes place. To render the former weighings available Sulphuryl Imide.

for this purpose, it would be necessary to determine the errors of As previously mentioned, wlien sulphuryl diamide is heated

| the barometers then employed.
the b

There would, perhaps, be no for a considerable time above its melting point it loses ammonia

great difficulty in doing this, but I was of opinion that it would and becomes converted into sulphuryl imide :

be an improvement to use a manometer in direct connection with

the globe, without the intervention of the atmosphere. With SO,(NH,), = NH, + SO.NH.

| respect to temperature, also, it was thought better to avoid all The best temperature for the rapid production of sulphuryl ' further questions by surrounding the globe with ice, as in Reg. imide is 200°-210". The evolution of ammonia at this tempera

| nauli's original determinations. ture is very vigorous, occurring with much frothing, but after

The Manometer. a lime dimini-hes and finally ceases, the mass becoming eventu. ally solid. To purify it from impurities the solution in water

The arrangements adopted for the measurement of pressure is treated with a solution of silver pitrate when the silver com- must be described in some detail, as they offer several points of pound of sulphuryl imide, SO,NAg, is precipitated, and may be i

novelty. recrystallised in long acicular crystals, first from water slightly

The object in view was to avoid certain defects to which acidified with nitric acid, and finally from pure water.

ordinary barometers are liable, when applied to absolute Upon decomposing the silver compound with the calculated

measurements. Of these three especially may be formu. quantity of diluie hydrochloric acid an aqueous solution of free

lated :sulphuryl imide is obiained, which reacts strongly acid, and

(a) It is difficult to be sure that the vacuum at the top of the liberates carbon dioxide from carbonales. Upon evaporation,

mercury is suitable for the purpose. however, it decomposes, and deposits hydrogen ammonium

(6) No measurements of a length can be regarded as satisfacsulphate. Even evaporation in vacuo is sufficient to decompose

tory in which different methods of reading are used for the two il, so that crystals of the imide itself have not been obtained.

extremities. It exists, however, in the solid form, although soinewhat con

(c) There is necessarily some uncertainty due to irregular reTaminated with smaller quantities of other products, in the

fraction by the walls of ihe tube. The apparent level of the residue obtained by heating sulphuryl diamide as previously

mercury may deviate from the real position. described.

(d) To the above may be added that the accurate observation Salts of sulphuryl imide, however, are readily obtained. | of the barometer, as used by Regnault and most of his successors, either by decomposition of the silver salt with metallic chlorides. | requires the use of a cathetometer, an expensive and not always or by the neutrali-alion of solutions of sulphuryl imide with

satisfactory instrument. metallic oxides or carbonates.

The guiding idea of the present apparatus is the actual appli. The potassium salt, SO,NK, was obtained in the form of cation of a ineasuring rod to the upper and lower mercury surwell-developed colourless crystals hy adding a quantity of the faces, arranged so as to be vertically superposed. The rod silver salt to a hot solution of the calculated quanuity of potas. | AA, fig. I, is of iron (7 mm. in diameter), pointed below B. Slum chloride, removing the precipitated silver chloride by fila | At the upper end, C, it divides at the level of the mercury into tration, and evaporating the solution. Both the solution and a sort of fork, and terminates in a point similar to that at B, and, the salt are very stable; it requires long boiling with acids to

| like it, directed downwards. The coincidence of these points convert it into sulphuric acid. When the dry salt is heated it with their images reflected in the mercury surfaces, is observed ilecomposes with considerable violence and production of Aame.

| with the aid of lenses of about 30 mm. focus, held in position Nitrogen and sulphur dioxide escape, and potassium sulphate

upon the wooden framework of the apparatus. It is, of course, and sulphi.e are left.

independent of any irregular refraction which the tube may The sodium salt, SO,N Na, obtained by neutralising a solu

exercise. The verticality of the line joining the points is tested tion of sulphuryl imide" with caustic soda and subsequent

without difficulty by a plumb-line. evaporation, forms small crystals, which decompose upon heat

The upper and lower chambers C, B are formed from tubing ing in a manner similar to ihe crystals of the potassium salt.

of the same diameter (about 21 mm. internal). The upper The ammonium salt, SO,NNH,, iso meric with sulphury!

communicates through a lap, D, with the Töppler, by means of diamidle, was likewire obtained in colourles: needles by neu.

which a suitable vacuum can at any time be established and Tralisatiou of the free imide with amm»nia. It is interesting to

tested. In ordinary use, D stands permanently open, but its note that this substance is not capable of being converted into

1 Abstract of a paper read by Lord Rayleigh before the Royal Society on its isomer by repeated crystallisation, but is partially so con. | March 23.

introduction was found useful in the preliminary arrangements and in testing for leaks. The connection between the lower chamber B and the vessel in which the pressure is to be verified takes place through a side tube, E.

The greater part of the column of mercury to which the pressure is due is contained in the connecting tube FF, of about 3 mm. internal diameter. The temperature is taken by a thermometer whose bulb is situated near the middle of FF. Towards the close of operations the more sensitive parts are protected by a packing of tow or cotton-wool, held in position between two wooden boards. The anterior board is provided

under microscopes by comparison with a standard scale, before the apparatus is put together. As the rod is held only by the rubber connexions, there is no fear of its length being altered by stress.

The adjustment of the mercury (distilled in a vacuum) to the right level is effected by means of the tube of black rubber LM, Terminating in the reservoir N. When the supply of mercury to the manometer is a little short of what is needed, the connexion with the reservoir is cut off by a pinch-cock at 0, and the fine adjustment is continued by squeezing the tube at P between a pair of hinged boards, gradually approximated by a screw. This plan, though apparently rough, worked perfectly, leaving nothing to be desired.

It remains to explain the object of the vessel shown at Q. In the early trials, when the rubber tube was connected direcily to R, the gradual fouling of the mercury surface, which it seems impossible to avoid, threatened to interfere with the setting at B. By means of Q, the mercury can be discharged from the measuring chambers, and a fresh surface constituted at B as well as at C.

Connexions with Pump and Manometer. Some of the details of the process of filling the globe with gas under standard conditions will be best described later under the head of the particular gas; but the general arrangement and

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with a suitable glass window, through which the thermometer may be read.

It is an essential requirement of a manometer on the present plan that the measuring rod pass air-tight from the upper and lower chambers into the atmosphere. To effect this the glass tubing is drawn out until its internal diameter is not much greater than that of the rod. The joints are then made by short lengths of thick walled india-rubber H, G, wired on and drowned externally in mercury. The vessels for holding the mercury are shown at I,K. The distance between the points of the rod is determined

the connexions with the pump and the manomeler are common to all. They are sketched in Fig. 2, in which S represents the globe, T the inverted bell-glass employed to contain the enveloping ice. The connexion with the rest of the apparatus is by a short tube U of thick rubber, carefully wired on. The tightness of these joints was always tested with the aid of the Toppler X, the tap V leading to the gas generating apparatus being closed. The side tube at D leads to the vacuum chamber of the manometer, while that at E leads to the pressure chamber B. The wash oui of the tubes, and in some cases of the generator, u as aided by the Töppler. When this operation was judged to be complete, V was again closed, and a good vacuum made in the parts still connected to the pump. W would then be closed, and the actual filling commenced by opening V, and finally the lap of the globe. The lower chamber of the manometer was dow in connexion with the globe, and through a regulating tap (not shown) with the gas-generating apparatus. By means of the Toppler, the vacuum in the manometer could be carried to any desired point. But with respect to this a remark must be made. It is a feature of the method employed that the exhaustions of

1 Due to von Jolly,

the globe are carried to such a point that the weight of the add 0.00056 to the apparent weight, so that the result for air residual gas may be neglected, thus eliminating errors due to a becomes second manometer reading. There is no difficulty in attaining

2-37717. this result, but the delicacy of the Töppler employed as a gauge is so great that the residual gas still adinits of iolerably accurate This is the weight of the contents at oo and under the pressure measurement. Now in exhausting the head of the manometer defined by the manometer gauge at 15° of the thermometer. it would be easy to carry the process to a point much in excess The reduction to standard conditions is, for the present, post. of what is necessary in the ca e of the globe, but there is evi. poned. dently no advantage in so doing. The best results will be

Oxygen. obtained by carrying both exhaustions to the same degree of perfection.

This gas has been prepared by three distinct methods : (a) The Water Contents of the Globe.

from chlorates, (6) from permanganate of potash, (c) by

electrolysis. The globe being packed in finely-divided ice, was filled with In the first method mixed chlorates of potash and soda were boiled distilled water up to the level of the top of the channel employed, as recommended by Shenstone, the advantage lying through the plug of the tap, that is, being itself at oo, was filled in the readier fusibility. Two sets of five fillings were effected with water also at oo. Thus charged the globe had now to be with this oxygen. In the first set (May, 1892) the highest result weighed; but this was a matter of some difficulty, owing to was 2'6272, and the lowest 2.6266, mean 2.62691. In the the very small capacity available above the tap. At about go second set (June, July, 1892) the highest result was 2.6273 and there would be a risk of overflow. Of course the water could the lowest 2.6267, mean 2 62693. be retained by the addition of extra tubing, but this was a com The second method (6) proved very convenient, the evolution plication that it was desired to avoid. In February, 1882, of gas being under much better control than in the case of during a frost, an opportunity was found to effect the weighing chlorates. The recrystallised salt was heated in a Florence in a cold cellar at a temperature ranging from 4° to 7o. The flask, the wash out, in this case also, being facilitated by a weights required (on the same side of the balance as the globe vacuum. Three fillings gave satisfactory results, the highest and its supports) amounted to o'1822 gram. On the other side being 2-6273, the lowest 2:6270, and the mean 2'62714. The were other weights whose values did not require to be known gas was quite free from smell. so long as they remained unmoved during the whole series of By the third method I have not as many results as I could operations. Barometer (corrected) 758.9 min. ; temperature 6° 3. have wished, operations having been interrupted by the break:

A lew days later the globe was discharged, dried, and re age of the electrolytic generator. This was, however, of less placed in the balance with tap open. 1834-1701 grams had importance, as I had evidence from former work that there is now to be associated with it in order to obtain equilibrium. The no material difference between the oxygen from chlorates and difference,

that obtained by electrolysis. The gas was passed over hot 1834-170-0'182=1833988,

copper, as detailed in previous papers. The result of one filling,

with the apparatus as here described, was 2.6271. To this may represents the weight of the water less that of the air displaced be added the result of two fillings obtained at an earlier stage of by it.

the work, when the head of the manometer was exhausted by an It remains to estimate the actual weight of the air displaced independent Sprengel pump, instead of by the Töppler. The by the water under the above mentioned atmospheric conditions. | value then obtained was 2.6272. The results stand thus :It appears that, on this account, we are to add 2314, thus obtaining

Electrolysis (2), May, 1892

2.6272 1836'30

2.6271 Chlorates (5), May, 1892

... ...

2.6269 as the weight of the water at oo which fills the globe at o'.

, (5), June, 1892

2.6269 A further small correction is required to take account of the

Perinanganale (3), January, 1893 .. 26271 fact that the usual standard density is that of water at 4' and not at oo. According to Broch (Everett's “C.G.S. System of

2.62704 Units "), the factor required is o'99988, so that we have

Correction for contraction ... O'00056 1836-30

2.62760

Mean

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Air.

It will be seen that the agreement between the different as the weight of water at 4° which would fill the globe at oo.

methods is very good, the differences, such as they are, having all the appearance of being accidental. Oxygen prepared by

electrolysis is perhaps most in danger of being light (from conAir drawn from outside (in the country) was passed through | tamination with hydrogen), and that from chlorates of being a solution of potash. On leaving the regulating tap it traversed

| abnormally heavy. tubes filled with fragınents of poiash, and a long length of

Nitrogen. phosphoric anhydride, followed by a filter of glass wool. The

This gas was prepared, in the usual manner, from air by arrangements beyond the regulating tap were the same for all the gases experimented upon.

removal of oxygen with heated copper. Precautions are reIn deducing the weight of the gas we compare each weighing

quired, in the first place, to secure a sufficient action of the "full" with the mean of the preceding and following weights

reduced copper, and secondly, as was shown by v. Jolly, and "empty," except in the case of October 15, when there was no

later by Leduc, to avoid contamination with hydrogen which

may be liberated from the copper. I have followed the plan, subsequent weighing empty. The results are

recommended by v. Jolly, of causing the gas to pass finally over September 27 ... ... ... 2'37686

a length of unreduced copper. The arrangements were as

follows:
... 2-37651
October

Air drawn through solution of potash was deprived of its
... ... 2-37653
... 237646

oxygen by reduced copper, contained in a tube of hard glass

heated by a large flame. It then traversed a U-tube, in which 237668 237679

was deposited most of the water of combustion. The gas, prac... 237647

tically free, as the event proved, from oxygen, was passed, as a

further precaution, over a length of copper heated in a comMean ... ... ... 2*37661

bustion furnace, then through strong sulphuric acid,' and altei

wards back through the surnace over a length of oxide of copper. There is here no evidence of the variation in the density of air

It then passed on to the regulating tap, and thence through the suspected by Regnault and v. Jolly

remainder of the apparatus, as already described. In no case To allow for the contraction of the globe (No. 14) when

1 There was no need for this, but the acid was in position for another weighed empty, discussed in my former papers, we are to purpose.

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