complete confirmation of the burden of this paper, it only needs that we should obtain the corresponding diphenyl citramide, (C12H308) Ph2N.

Finally, it is plain that if these principles be applied to the identification of organic radicals, that the diatomic alizarine, and an infinitude of others, will yanish into a clear comprehension of the simple truth.

ON THE DISSOCIATION OF OXIDE OF
MERCURY,
By J. MYERS.

DEBRAY*, in 1867, promised that he would publish his researches on the dissociation of mercury, but he has not yet done so. No older researches on this subject exist, except those of Pelouze and Gay-Lussact, from which it resulted that the decomposition of the two modifications of that oxide begins at the same temperature. My experiments only relate to the red modification of the oxide of mercury, which, of course, I took care to prepare in pure state, so as to be quite free from suboxide, which is decomposed at 100°. The red oxide of mercury of commerce always contains suboxide; and I therefore prepared the oxide by ignition (gentle heating rather) of the nitrate prepared from pure mercury, obtained by reducing crystalline cinnabar by means of iron, the metal being next dissolved in nitric acid. The oxide so prepared was not, however, quite free from suboxide, which was eliminated by heating it with nitrate of ammonia. The oxide was put into a glass tube which had previously been weighed, and which was connected with a Geissler pump: Prior to this I had, however, measured-(1), the cubical capacity of the balloon of the pump, taking a mark made on it as starting point; (2), the cubical capacity of the tube and other parts of the apparatus; (3), the diameter of the barometer tube of the pump. This enabled me to control the indications of the manometer (pressure gauge) by means of the balance, and I found that they agree

with each other.

The tube filled with oxide was in these experiments heated to the requisite temperature by the following means:-(1), in an air bath kept at a constant temperature by the modified Schlösing's temperature regulator; (2), in a bath of mercury and sulphur for temperatures of 350° and 440°; (3), a bath of sulphur and zinc for temperatures of 400° to 560, the heat being regulated by adjusting the gas-flame by a well-made tap. The determination of these high temperatures was effected by the aid of Berthelot's air thermometer. Before weighing the tube it was always cooled by the aid of a Liebig condenser. In the first experiments the tube was heated to 105.5° for an hour; the manometer did not indicate any pressure. In the second experiments the tube was heated to 150° for an hour; the result was that oxygen was evolved, but in too small a quantity to exert any pressure; a deposit of mercury was also visible. At 240° the tension of the mercury was, after an hour's heating, 2 m.m., and did not increase by continuing the experiment. For about two hours the temperature was kept at 293°, and the tension was 2m.m. No increase was observed during the second hour. These four experiments prove that the maximum of tension is reached in a short time, while it (the tension pressure) is very small, and amounts only to a very small fraction of the atmospheric pressure. In the fifth experiment I heated the tube to 350° in an air bath, the temperature of which was kept constant, and determined by an air thermometer. After having continued the application of heat to the tube for about the same time as in the previous experiments, the pressure exerted by the oyxgen amounted to 8 m.m., which was found to be the maximum for this temperature. I heated the tube to 400° for five

Comptes Rendus, 1867, 603. + Ibid., vol., xvi. 310,

hours; at the end of this period the manometer still rose (mercurial gauge), the pressure was 16 m.m.

It was not an easy matter to keep the temperature of the boiling sulphur bath constant. The tube was in it for thirteen hours; after seven hours the pressure was 39 m.m., and it increased during the last 6 hours by 27 m.m. The tube was next transferred to a bath of molten zinc kept at 560°. After seven and a quarter hours the pressure of the oxygen under these conditions was 343 m.m. After three hours and a half the pressure was 271'5, and by observing and noting the reading of the manometer every quarter of an hour, I found that maxima and minima occur as exhibited by the following figures:304, 369, 3155, 323, 329'5, 334'5, 339, 343.

This experiment also enabled me to estimate the melting-point of the ordinary zinc of commerce, which I found to be 440°. The course of the experiments just alluded to, and the fact that in no instance a decrease of the tension of the oxygen occurred either when the cooling was rapidly or slowly effected, rendered probable the view with which I undertook these researches. looseness of the combination of mercury and oxygen made it reasonable to expect that an anomaly of the dissociation should arise, and this the more so if Pfaundler's definition of dissociation is viewed as correct. But the

The

main point of that definition, viz., that by a given constant temperature as large a number of molecules are split up as are by contact reunited, so that, in fact, a condition of equilibrium is obtained (maximum of tension), does not, I think, hold good in the case of oxide of mercury; because only the first parts of the definition just given obtains with it and not the second.

In order to make sure of the correctness of my first researches, the results of which were somewhat contrary to my expectations, I again placed the tube in a bath of boiling sulphur, having first filled the apparatus with 66 m.m. of oxygen, the same quantity left in the apparatus at a previous experiment. The stopcock of the air pump was so adjusted that the balloon of the pump did not form and a half hours, the pressure of the O increased by The tube was heated for twenty part of the apparatus. 60 m.m.; yet in this case also, the increase of the pressure tabulated form :was not uniform, as may be seen from the subjoined Reading of the Manometer.

Duration of Experiment. Hours.

Increase per Hour.

m.m.

2.13 2:54 3'45 3'50 2'50

to the lake of Myvatn. At the present time, the greatest amount of volcanic activity is manifested at the southern end of this line, in the district some peculiarities of which I now propose to bring before you.

In the last century it was the northern end of the volcanic diagonal, near about Myvatn, where, according to the Icelandic records, the kind of pseudo-volcanic action was most vigorous, by which the boiling springs are set in operation and the sulphur deposits are formed; but a violent eruption of the mud volcano, Krabla, to a great extent buried the then active strata beneath enormous masses of volcanic mud and ashes, so that the energy has been probably transferred along the line southwards.

The Krisuvik springs are in a valley beneath some high mountains (see plan; the shaded portion represents the

|

sulphur beds surrounding the active springs). They are reached by a track, so narrow that there is no more than room to enable horses to pass along it-across the brink and along the side of a vast hollow, termed the "kettle." Following this rude track, the "Ketilstip," the summit of the range of hills, is reached which overlooks Krisuvik. In the midst of a green and extensive morass, interspersed with a few lakes, are cauldrons of boiling mud, some of them 15 feet in diameter, numberless jets of steam, and boiling mud issuing from the ground, in many instances to the height of 6 or 8 feet. Sir George Mackenzie (who was accompanied by Sir Henry, then Doctor, Holland, now the President of the Royal Institution), in his justlycelebrated "Travels in Iceland, in 1810," gives a vivid word-picture of the scene. "It is impossible," he writes, "to convey adequate ideas of the wonders of its terrors. The sensation of a person, even of firm nerves, standing on a support which feebly sustains him, where literally fire and brimstone are in incessant action, having before his eyes tremendous proofs of what is going on beneath him, enveloped in thick vapours, his ears stunned with thundering noises. These can hardly be expressed in words, and can only be conceived by those who have experienced them."

The photographs which I have the honour to exhibit are many of them taken from paintings made on the spot by Mr. Waller, a nephew of Prof. Huxley, who certainly, by his faculty of close and accurate observation, does great credit to his distinguished relative. I have obtained from him corroboration of many facts which, though they might be expected to be noted by a chemist, or physicist, do not lie within the ordinary vocation of an artist.

On the other side of the mountains, subterranean heat is also manifested, and hot springs, accompanied by sulphur beds, are also found; but they have not been as thoroughly examined as those in the valley, and are represented as being less active.

Mr. Seymour, who has spent many months at Krisuvik, tells me that the sulphur beds on this side have been sub

merged by the clays washed down by the winter rains, and are, for the most part, now completely overgrown with grass. On digging beneath the surface, however, the sulphur earth is found to be only a short distance down, and on analysis the percentage of sulphur in one bed, 116 yards long, running up the side of the mountain, was discovered to range between 64 and 65.5. Here the earth was completely cold, and all further deposition of sulphur appeared to have ceased.

In the valley itself the springs are not always visible at the surface, being so completely covered by the earth, that it is only by piercing through the crust of indurated sulphur earth that their presence is discovered. Sometimes the explorer is made unpleasantly aware of the insecure nature of his footing by falling through, and thus opening up a fresh thermal spring. The late Sir William Hooker, when visiting this place, in endeavouring to escape a sudden gust of strongly odourous vapour, jumped into a mass of semi-liquid hot earth and sulphur-and but for his presence of mind, in throwing himself flat upon the ground, would have sunk to a considerable depth; as it was, the difficulty of extricating himself was very considerable.

The surface of the ground is covered in many places with a crust of 2 to 3 feet in depth of almost pure sulphur ;

It has been suggested by those who wish to utilise the immense sulphur-producing power of this wonderful locality, that chambers should be erected (Sir George Mackenzie), or walls built up (Dr. Perkins), by which means, the force of the wind being broken, the sulphur would be quietly floated to the ground, instead of being carried up the sides of the hills, and thus more widely distributed.

With little variation the general appearance of the "solfataras," over the space of 25 miles along the volcanic diagonal, is much alike; an elevation about 2 feet high and 3 feet in diameter, which is composed of a dark bluishblack viscid clay, forms a complete circle round the mouth of a medium-sixed spring. The water is sometimes quiescent, and sunk about 2 feet within the aperture; at other times it is ejected, with great hissing and roaring noise, to the height of from 5 to 8 feet. At all times clouds of steam, strongly impregnated with sulphuretted hydrogen and sulphurous acid gas, issue from the orifice,

both of which, during an eruption of the water, are greatly augmented in quantity. From the dark-coloured and evelated margin of the fountain the yellow crust of crystallised sulphur extends a great distance in every direction. Columns of steam ascend from numberless points in the whole district, which are thus impregnated; and thus it is that, apparently for ages past, sulphur has been gradually heaped up in this locality till there are actually hills, which, as far as they have yet been pierced, show sulphur-earth to be their main constituents; hence they have acquired the name of the Sulphur Mountains.

The soil is of different colours, but most generally white. It is, in the vicinity of the springs, a viscid earth, less plastic than clay, and more readily broken.

When excavations are made into this earth, it is found to be composed of multitudinous layers, of different colours or shades of colour, each layer being quite distinctly divisible from those above and below it, though frequently no more than an inch or two in thickness.

It is much to be regretted that the good example set by Olafsen and Povelsen, of investigating the nature of the earth's crust round about the solfataras by piercing the soil, has not been more frequently carried out. In the summer of last year one of the suggestions which I made, for the instruction of an expedition to this place, was that boring implements should be taken out and extensively used; but accident prevented the necessary appliances being forthcoming at the right time. I believe, however, that one of the chief features in the expedition which is to set out in March, will be the thorough examination, to as great a depth as practicable, of the strata in various parts of the sulphur-valley.

The spring chosen by Olafsen and Povelsen as the subject of their first experiment, was one which had made its appearance since the preceding winter, and which was

and jets of steam. The ground was still covered with lovely verdure, and charming flowers were abundant, even at the very verge of the cauldron of hideous hue and odour. A short distance from this opening they established their boring apparatus. The sequence of the layers was as follows:

1. Three feet of reddish-brown earth, of a fatty consistence, of the ordinary temperature; at the bottom heat was perceptible to the touch.

2. Two feet of a firmer kind of earth, nearly the same in colour as the first layer, unctuous to the touch. 3. One foot of a lighter kind of soil.

4. Five feet of a very fine earth of different colours, the first 2 feet being veined red and yellow, with streaks of blue, green, red, and white intermingled. The lower portion of this earth was somewhat firmer than that which covered it. The heat of this thick bed was so great that the soil extracted by the auger could not be handled until it had been for some time exposed to the air. 5. One foot of a compact greyish-blue earth. 6. In tapping this bed, which was 4 feet 9 inches in thickness, and consequently at a depth of about 12 feet, water was first met with. It was found by comparison that the level of the water in the boiling mud spring coincided at this time with that of the water thus discovered. The heat was now very great, and a constant hissing and bubbling could be heard as proceeding from the bottom of the hole which had been made.

7. Nine inches of greyish-blue earth.

8. One foot six inches of a similar unctuous earth, containing many small white stones. This was the hottest layer of any yet pierced; the buzzing humming noise was now much louder than before.

9. Three feet of the same kind of clay, but much harder and more compact; this layer was also full of small, round, white stones.

10. Six inches of a violet-tinged earth, very greasy to the touch. In this bed the heat sensibly diminished.

II. One foot six inches of red and blue clay intermingled. The heat continued to diminish very fast.

12. One foot of reddish-looking clay, the temperature remaining about the same.

13. Six inches of yellow and red clay.

14. One foot of a greenish-coloured earth, much less coherent than the previous layers. Here the heat again began to increase.

15. One foot six inches of blue clay, filled with small pieces of white tufa. This bed was much hotter than either that above or that below it.

16. One foot three inches of soft blue clay.

17. Nine inches of an earth, easily pulverised when dry, which, whilst moist, was of a violet colour; on exposure to the air, however, this rapidly changed to a chocolatebrown. The heat was again augmented as the centre of the bed was approached.

At thirty-two feet the full length of the boring implements was used up; but, from the set of the country in the vicinity, the experimenters believed they were close upon basaltic rock, when the heat probably ceased.

In digging for the peculiar kind of browncoal which they call "surturbrand" (a kind of fuel very much resembling Irish bog-oak, which can be used for like purposes), the inhabitants frequently go as deep as 28 feet. They report that before reaching this depth they frequently pass through three or four beds of blue, yellow, and brown clay, and almost invariably find that the layers of blue clay are much hotter than any of the other strata.

A second trial of the soil was made in the neighbourhood of some recent springs, further to the east. The activity of the agencies at work here appeared to be greater than in the former case, and to have been longer in operation. The whole surface was thickly covered with sulphur in a finely-divided state; there was much gypsum, and a large efflorescence of feathery alum. Thousands of very minute holes were discoverable on close examination, through

which continuous jets of steam, sulphuretted hydrogen, and sulphurous acid gases were emitted.

An attempt was made to dig with spades, but the soil was found to be so hot, whilst the footing was at the same time so insecure, that it could not be persisted it. A spot some distance further off was therefore pitched upon, where the earth was firmer and colder. The borer pierced through 6 feet of blue clay with great facility, the lowest portion being extremely hot. After this depth the earth became rapidly softer; at the depth of 7 feet the same peculiar bubbling noise before noticed was heard. Continuing to bore, the bottom of the hole appeared to be in a state of ebullition, a boiling liquid being ejected in the narrow space around the handle of the auger with extraordinary violence, and, no sooner was the tool withdrawn, than a thick black fluid was ejected from the orifice to the height of several feet. A short time afterwards the jet ceased, the subterranean fire appeared to have expended its fury, but it soon re-commenced with re-doubled activity to dart forth fresh jets of steam and black muddy water, continuing to boil and dance with but slight intermission. It appeared, therefore, evident that the result of this experiment was the premature formation of a fresh hot spring, which would otherwise have been, perhaps, a considerable time in forcing its way to the surface. (To be continued.)

PROCEEDINGS OF SOCIETIES.

GLASGOW PHILOSOPHICAL SOCIETY.

(CHEMICAL SECTION).

Ordinary Meeting, February 24th, 1873.

= 3.00 19

=II cwts. 3 qrs.

In the second part of his paper the author treated of anthracene, commencing with the discovery by Dumas and Laurent, in 1832 of a hydrocarbon, to which they gave the formula C15H12, and applied the name paranaphthaline. On making further examination, Laurent named the body anthracene. Fritzsche, in 1857, discovered a substance very closely resembling Dumas and Laurent's compound, and he assigned C14Hro as its formula. Anderson, in 1862, described a hydrocarbon of the same formula under the name of anthracene, although many of his observations differed essentially from those made by

A PAPER

Chair.

was read on "The Chemical History of Anthracene, and its Production from Coal-Tar," by Mr. R. F. SMITH, Glenpark Chemical Works, Glasgow. The author first devoted a considerable amount of attention to the nature and composition of coal-tar, incidentally tracing its history from before the Christian era down to the present time. Exact researches into the proximate composition of coal-tar were not attempted before 1848, the basic constituents being attaked first. Runge described carbolic, rosolic, and brunolic acids, Laurent confirming the existence of the first under the name of phenole. Hofmann, Fritzsche, Erdmann, Zinin, Anderson, Reichenbach, Young, Faraday, Mansfield, and other chemists each contributed to extend the knowledge of the composition of coal-tar; and many distinct chemical compounds were obtained from it. Proceeding to notice the chemistry of coal-tar as known at present, the author said that the substance varies much in specific gravity, some samples being as low as 100, and others as high The further away from retorts the lighter it is, the heaviest portion condensing first, while the condensertar, if it contains enough of oils to retain the naphthaline in solution, is very light. The more fluid the tar, the richer it is in naphtha. Crude naphtha is frequently found in considerable quantity, free from pitchy matter, in the "dreeps" between the purifiers and the gas-holder; and in the holder-tank it sometimes accumulates on the surface of the water. English tar generally contains less fluid matter than Scotch tar. In distilling the tar, water and naphtha are first separated, then the light oil, next ordinary creosote, or pitch oil, and sometimes there is obtained a further distillate, known as green oil, green grease, or heavy pitch oil, the residue in the boiler being pitch, which varies in hardness according to the amount of oil contained in it. The following is the average composition of coal-tar, as determined by the experience of many years in an English tar distillery :

as 15.

anthracene by heating benzyl chloride with water to 180° C.; and in the same year Berthelot showed that it was obtainable by the action of heat on various simple hydrocarbons, such as toluol, a mixture of styrol and benzol, or a mixture of benzol and ethylene. He also confirmed Anderson's observations. Graebe and Liebermann, in 1868, obtained from alizarine a hydrocarbon posessing the same properties and composition as Anderson's anthracene. After giving an outline of the view generally taken of the constitution of anthracene, and showing its relation to benzol and other members of the aromatic group of hydrocarbons, Mr. Smith described the various methods by which anthracene is produced on the large scale. Probably not more than 10 tons of the commercial anthracene of 95 per cent has yet been pro duced in all the Scotch tar distilleries together, but in England the manufacture is proceeding on a more extensive scale, and as knowledge extends, additional works are taking it in hand. The great practical difficulty in the way of distilling the pitch for its contained anthracene is to find a proper arrangement of flues for the regulation of the heat. What is wanted is a sharp, quickly applied heat, sufficiently powerful to coke the pitch in a proper manner, and yet not strong enough to melt the iron walls of the retorts. Clay retorts have been tried, but they do not appear to answer, owing to the intermittent nature of the heat required, partial cooling being necessary after each charge, to allow the coke to part properly from the retort. Ordinary coke ovens with condensing arrange ments do not suit, as part of the oil is burnt; the practical difficulties will, however, be overcome, and in many localities retorts for coking pitch have been in regular use for years. In working a charge, it is found that, under ordinary circumstances, all volatile matters can be driven off in about six hours; but the fire is still maintained a few hours longer, to get the coke hard enough. After cooling for some time, the coke is withdrawn and drenched with water. The first distillates in the operation are hydrogen gas and water vapour, with a little oil contain