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Of the New Process.-The chief distinctive feature of my process, as compared with the common one, consists in this, that the operator has complete and easy control of the temperature of the vapours given off in distillation, and consequently can readily cool these vapours to the lowest limit of temperature which the most volatile portion, under the circumstances, is able to bear and retain its vaporous condition. It will be seen at a glance that, under these conditions, the operator has it in his power to secure in any case the very largest possible amount of condensation of the heavier from the lighter vapours. The liquids resulting from the condensation of the less volatile portions of course fall back into the retort, while the vapours of the more volatile parts continue to go forward to a cold condenser, descending in the opposite direction, from which the condensed product falls into a special receiver. In this manner he is able to obtain in each succes sive operation a series of products which shall contain the minimum quantity of the less volatile constituents which a single distillation is capable of affording.

Of the common process, on the contrary, nearly the reverse of all this is true, the operator having no control whatever, being forced to receive the vapours at the temperature which they naturally acquire in passing from the retort, and laden with such proportion of the less volatile bodies as may be carried forward with them.‡‡

In the new process, perfect control of the temperature of the vapours is secured by simply conducting these vapours upward through a worm contained in a bath, aa,

Figs. 1 and 2,§§ the temperature of which is regulated by means of a separate lamp, b, Fig. 2, or by a safety furnace, p, as shown in Fig. 1. The bath may be of oil or water, or of metal for very high temperatures, as the case may require, and is furnished with a thermometer, t. That this bath may be equally adapted for the separation of liquids boiling below the common temperature, an empty vessel, c, Fig. 1 and 2, is permanently secured in the interior of the bath by means of straps of metal across the top to serve as a convenient receptacle for ice or iced water, by means of which a low temperature may be steadily maintained. This interior vessel also serves a good purpose in economising time and fuel in heating the bath, as it diminishes the quantity of oil required to cover the worm. It is made to extend to within about three inches of the bottom of the bath, and large enough to fill the greater part of the space in the centre of the coil. The bath and interior vessel are both made of sheet copper, with joints brazed so that they will bear a high temperature. I generally use also copper worms, especially in the earlier distillations, the quantities then operated upon being larger, as such worms are conveniently procured and not liable to break. In the larger sized apparatus, the tube of which the worm is made measures ten feet in length and half an inch in diameter. I have tried several lengths of worm and several diameters of tube, but not as yet with any special view of determining the precise proportions, in relation to the size of the retort, which would be best adapted to the purpose. There appears, however, to be nothing gained by increasing the length of the worm beyond what is required to reduce the temperature of the vapours to that of the bath I have in use three sizes of apparatus. The largest has a copper worm 10 feet long and inch bore; the medium size, a worm 5 feet long and 3 inch bore; and the smallest size, for very small quantities, a worm 1 foot 6 inches long and inch bore. Each of these has been found to answer a good purpose. The distillation may be conducted in a glass flask, or more conveniently in a glass retort of the form shown at d, Figs. 1 and 2. The body of this retort, as appears in the figure, is of the form of the corresponding part of the common retort, but which, in place of a long neck, has only a short tubulure, e, in the side, for escape of the vapours, and another tubulure, which the retort is charged.

The only apparatus of which I have any knowledge which can be regarded as bearing any analogy to my own is that employed in the rectification of alcoholic spirits on a manufacturing scale. In one of the older forms of this apparatus, that of Solimani, to which my attention was first called by a friend, after my process had been in use more than a twelvemonth, the temperature of a dephlegmator is kept within such limits as to give alcohol of any required strength more readily than by the common methods. The mode of construction of this apparatus is, however, only adapted to manufacturing, in the top, which contains the thermometer, and through purposes, and it could not be utilised in the more exact experiments required in scientific research. Either on account of its complication, or some other cause, the apparatus of Solimani has, I believe, long

eince been abandoned.

Mansfield (Quarterly Journal of the Chemical Society, 1849, i. 264), observing that "the boiling point of benzole is the same as that of alcobol of sp. gr. o 825," remarks that "any of the summary processes of rectification which are practised by distillers in the manufacture of alcoholic spirits are applicable to the separation of benzole from the less volatile fluids of naphtha;" and appeuded to his scientific treatise on coal tar, under the title "Of a Practical Mode of Preparing Benzole," goes on to describe a process for that purpose, which believe he had previously patented. It appears that Mansfield did not employ this process in his research, but obtained his benzole, as well as the other less volatile hydrocarbons, in the usual manner-by simple distillation. In the belief that no process of fractioning at all analogous to mine has ever been employed in scientific research, and that I am not in any way directly indebted to any of the devices of my predecessors, I have taken no special pains to consider these devices in much detail. I may say, however, that I have found no record of any one's ever having employed the oil bath and a separate fire to regulate a heated condenser, this being the essential feature on which the superiority of my process is based, adapting it at once to both high and low tenperatures and for the most delicate work.

The employment of bulbs above referred to, as proposed by Wurtz, is simply a modification of the old process. The bulb apparatus furnishes the same, or at most but slightly better, results than a simple retort, being no more than equivalent to increasing the height of the sides of the retort itself, without introducing any control over the accuracy of the results, the only advantage gained being that these results are obtained somewhat more quickly.

VOL. XII. No. 300.-SEPTEMBER 1, 1865.

the lower end of the elevated worm by means of a glass In the larger apparatus the retort is connected with tube of about the same diameter as the end of the worm. One end of this tube enters the retort at the lateral tubulure through a perforated cork, and the other end is joined to the end of the worm either by being firmly bound with a strip of cloth thickly covered with vulcanised caoutchouc such as is found in commerce-or by means of a perforated cork, which is made to fit the ends of both tubes as snugly as possible, and then tightly pressed together upon the joint by means of an iron clamp, as shown at g, Fig. 2. This clamp is figured on a larger scale at E. As it is highly important that all joints in the apparatus should be perfectly tight, inasmuch as the least leakage, when continued a long time, would cause in the aggregate a serious loss of material, I would call special attention to the clamp joint as the best which I have tried. Before falling upon this device I had used exclusively the vulcanised caoutchouc joints, which were found to answer a good

§§ We owe these illustrations to the kindness of the author, who has been good enough to forward them from America.

purpose in most cases, except that they required too frequent renewal. I have found the cloth covered with vulcanised caoutchouc preferable to the common caoutchouc tubing. In the smaller sizes of apparatus I have the end of the worm itself project far enough from the bath to connect directly with the retort by means of a perforated cork, without the use of an additional connecting tube.

The upper end, h, of the elevated worm is brought out through the side of the bath at a point about three inches below the top, so that, when working with a low temperature of the bath, the worm may still be completely covered with oil, and also give sufficient space above the worm for the expansion of the oil when higher temperatures are employed. To avoid contaminating the atmosphere of the laboratory with the disagreeable

fumes which are given off in large quantity from such a mass of heated oil, the top of the bath is tightly closed with a sheet iron cover, from which a small funnel, A, Fig. 1, conducts these fumes to a chimney. In the larger apparatus, the vapours which succeed in passing through the heated worm are conducted downward into a cooled worm contained in a bath of water, ii, Fig. 2, and the liquid product is collected in the receiver, k. The cold bath, i, contains two condensing worms-one for each apparatus-and is large enough to condense for both without the necessity of renewing the water. I have represented two apparatuses combined, as it will be found more economical of time to operate with two at once. In the smaller apparatus for the table, a Liebig condenser may be conveniently substituted for the cold worm, as shown in Fig. 1.

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For collecting liquids which boil below the common temperature, when such are present, I attach a refrigerator, B, Fig. 2, which is provided with two block tin condensing tubes-one for each apparatus. These are bent in a zigzag form, and attached to the inner sides of the refrigerator. The lower ends of the tubes extend through the end of the refrigerator far enough to form a convenient connexion with the second receiver, 1, Fig. 2, which communicates with the first receiver, k, by means of the glass tube, m.

In order to successfully collect and condense the vapours of such extremely volatile liquids as are now under consideration, it is of course indispensable that the apparatus should be constructed with very tight joints; and for greater convenience, but more especially to prevent breakage, such of the joints as require to be frequently taken apart should be made flexible. A very convenient and perfectly tight joint of this kind may be made as follows:-The short stationary tube, n, in the cork of the receiver, k, Fig. 2, is made with the opening somewhat divergent upward; the end, o, of the worm

is enough smaller than the inside diameter of the upper end of the tube, n, to leave room for a piece of caoutchouc tube to be drawn over it and still admit of its being inserted in the end of the tube, n; the flexible tube is drawn on far enough to prevent the drops which form on the end of the worm from coming in contact with the caoutchouc; a perfectly tight and convenient flexible joint is now made by pressing the tube, n, over the caoutchouc covering of the end of the worm, o. The joints of the receivers, ll, are made in the same manner.

The vapours which escape condensation in i pass through the receivers, kk and I, to the refrigerator, B, which contains ice or a mixture of ice and salt, are there condensed and fall back into the receivers, ll, which should stand in a wooden vessel also containing ice or a freezing mixture. The refrigerator, B, is made with double bottom and sides, with an inch space between, which is filled with pulverised charcoal. Being tightly covered, a charge of ice and salt will serve for a long day's operations without renewal. In this manner I have been able to collect in considerable quantity bodies

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AVIVERSITY

OF THE

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boiling nearly at o° C., and this from mixtures in which such bodies had been quite overlooked by previous investigators.

It will be observed, on reference to Fig. 2, that the larger distilling apparatus is represented as standing in a brick fire-place, with brick work, CC, a few inches high, built up in front, and a sheet iron apron, DD, folded above. This is for security against fire in case of accident, either to the retort or hot bath of oil. As arranged, the contents of either or both of these could run out and burn without danger to the operator or the premises, as the brick work in front would prevent the liquid from spreading beyond the fire-place, and the dropping of the sheet iron apron would cause an additional draught, and thus insure the passage of the flames into the chimney. Instead of placing the apparatus in a fire-place, where that is not convenient, equal security against accidents may be attained by the use of my safety heating lamp,||||| q, Fig. 1, to heat the retort, and safety furnace, p, containing a Bunsen's burner, for heating the bath. The bottom of this furnace, and also a large part of the sides, is formed of wire gauze, such as described for the safety lamp.¶¶ The gauze upon the bottom need not be permanently attached to the furnace, but may be simply laid over an opening cut in the stool or board on which the furnace is to be placed; if the furnace be then set upon it, taking care that the joint shall be tight around the edge, nothing more will be required. A strip of vulcanised caoutchouc, about an eighth of an inch in thickness, is riveted around the edge of the opening for the door. Against this the door tightly closes, so that no ignition can take place through the cracks which would otherwise remain under the edges of the door,

We have here, then, a rare example of the precipitation of one of these salts under conditions which do not appear to affect the other. Chlorothallate of ammonia, therefore, would appear to be useful in the laboratory as a means of quickly distinguishing bismuth from lead. Whether it is of use in completely separating one of these metals from the other remains to be decided. Bromothallate of ammonia has the same reaction as the chlorothallate.

It may be as well to add that chlorothallate of ammonia is most easily formed by treating chlorothallic ether or alcohol (see CHEMICAL NEWS, vol. ix., p. 241) with sal ammoniac. The salt is obtained in the form of beautiful colourless six-sided tables, which are soluble in alcohol and in water.

cent.

PHARMACY, TOXICOLOGY, &c.

On Diffusion of Fluids by the Atomiser for the Purposes of Deodorisation and Disinfection. AT the recent meeting of the British Medical Association, Dr. Richardson explained a process he had adopted for applying the atomiser for the purpose of deodorisation. He made a mixture by adding iodine to solution of peroxide of hydrogen until saturation occurred, and afterwards concentrated sea-salt in proportion of 2 per In this combination a water was produced like sea-water, and which was rendered active by being in one of Krohne's hand atomisers could be diffused in charged with free iodine and ozone. The solution placed the finest state of distribution at the rate of two fluid For an apparatus to stand upon the table, the safety ounces in a quarter of an hour; but in an ordinary bedlamp and furnace are especially desirable. I have also the air so active that ozone test-papers were discoloured room or sitting-room one ounce was sufficient to render used them for the larger apparatus, placed upon the floor of the laboratory. As a practical test of the by it to the highest degree of Moffatt's scale in from five to ten minutes. For charging the sick room rapidly security which they afford, I may relate an incident and effectually with active air-in a word, with sea-air which happened to myself. I had left the laboratory Dr. Richardson said this plan was by far the most for a short time with such an apparatus in full opera-effective of any he had known. A nurse could put the tion, the retort containing nearly a quart of light petro- apparatus into action at once, and could deodorise hour leum boiling below 100° C. Having been detained longer by hour, according to the directions of the Medical than I expected, on returning I found the laboratory filled with the vapours of hydrocarbons; and on approaching the retort, found that the caoutchouc joint, connecting the retort with the elevated worm, had failed, and that the larger portion of the liquid had distilled into the room, having been mainly condensed in the upper worm, and conducted thence down the outside of the retort into the safety lamp. This process was still going on, the lamp being highly heated from the excess of fuel thus added to it, but no ignition took place outside the lamp. Although this experiment was rather injudicious, it furnishes a valuable test of the efficiency of the safety lamp and furnace.

(To be continued.)

Chlorothallate of Ammonia as a Reagent,
by M. NICKLES.

CHLOROTHALLATE of ammonia completely precipitates
nitrate of bismuth. The precipitate is chlorothallate of
bismuth in the form of a white powder.

Under the same conditions solutions of salts of lead remain transparent, with the exception of the basic acetate, which becomes cloudy, the cloudiness, however, disappearing on agitation.

American Journal of Science, 1862 (2), xxxiii. 275.
Loc. cit.

Practitioner.

Calabar Bean-Its Alkaloid, by FERDINAND F. MEYER. SOME sixty beans were kindly contributed by Professor Torrey towards the preparation of the alkaloid. A preliminary examination proved that the base, as well as its its salts, were colourless, and whenever they became coloured a loss was sustained. To avoid evaporation as much as possible, I adopted the following method:The beans were reduced to moderately fine powder, and repeatedly digested with 85 per cent. alcohol, and then displaced with alcohol of the same strength. The tincture was subjected to distillation, while the residual powder was boiled with dilute sulphuric acid until all of the starch had disappeared. The residual extract from the tincture and the acid solution were then mixed, filtered and precipitated with iodohydrargyrate, the precipitate washed by decantation, transferred to a cask with good stopper, in which it was treated with a strong solution of protochloride of tin in tartrate and bicarbonate of soda, and then with ether. The colourless ethereal solution was distilled, the soft residue redissolved in dilute sulphuric acid, and again treated with ether and ammonia. The alkaloid was now obtained as an almost colourless mass, readily combining to form crystalline salts, but without any distinctive reactions.

On dissolving the impure alkaloid in acids, a reddish- solved off, and the same physical impression may be brown substance separates, which, from the experiments made to produce a second picture by a simple application made with it, may be assumed to be inert.-Amer. of a developing agent. ·Jour. of Pharmacy.

PHOTOGRAPHY.

On the Nature of the Invisible Photographic Image, by M. CAREY LEA.

SOME experiments in which I have lately been engaged seem to me to finally settle the long-contested question as to the nature of the invisible photographic image, and I hasten to write a very brief description of them.

The view that the change which takes place in iodobromised plate in the camera is a purely physical one, that no chemical decomposition takes place, and neither liberation of iodine nor reduction of silver, has obtained a pretty general acceptance. But latterly it has been opposed by two distinguished photographers-Dr. Vogel and Major Russel. The former affirms that iodide of silver is never sensitive unless there is a body present capable of taking iodine from it under the influence of light. And Russel believes that the developed image is chiefly produced at the expense of the silver haloid in the film.

The following experiments seem to me to decisively close this controversy in favour of the physical theory :Experiment 1.-If the iodide or bromide of silver in the film undergoes decomposition in the camera, and, still more, if the developed image is formed at its expense, the film of iodide-bromide must necessarily be greatly consumed in the development under the dense portions of the negative, which it has contributed to form. To settle this point, I exposed and developed an iodobromised plate in the ordinary manner. Then, instead of removing the unchanged iodide and bromide by fixing in the ordinary manner, I took measures to remove the developed image without affecting the iodide and bromide. This I succeeded in doing with the aid of a very weak solution of acid pernitrate of mercury. Now, if the iodide, or bromide, or both, had been in any way decomposed, to form, or aid in forming the developed negative image, when this came to be removed there should have been left a more or less distinct positive image, depending upon varying thicknesses of iodide and bromide in the film, much like a fixed negative that has been completely iodised. Nothing of this sort was visible, the film was perfectly uniform, just as dense where an intense sky had been as in those parts which had scarcely received any actinic impression, and looking exactly as it did when it first left the camera, and before any developer had been applied.

This experiment seems sufficiently decisive. But the following is far stronger.

Experiment 2.-A plate was treated in all respects as in No. 1, except that the application of the nitrate of mercury for removing the developed image was made by yellow light. The plate now showing nothing but a uniform yellow film, was carefully washed, and an iron developer, to which nitrate of silver and citric acid had been added, was applied. In this way the original image was reproduced, and came out quite clearly with

all its details.

Now, as every trace of a picture and all reduced silver had been removed by the nitrate of mercury, it is by this experiment absolutely demonstrated that the image is a purely physical one, and that after having served to produce one picture, that picture may be dis

P.S.-Since the above was written, I have repeated the experiment with a pyrogallic development with similar results. Both the first and second developments may be made with an iron developer or both with a pyrogallic. The experiment succeeds without the least difficulty in either way.-Am. Jour. Science and Arts, vol. xi., No. 118.

PROCEEDINGS OF SOCIETIES.

COLLEGE OF PHYSICIANS. "On Animal Chemistry." A course of Six Lectures by WILLIAM ODLING, M.B., F.R.S., F.R.C.P. Friday, May 5, 1865.

LECTURE 4.

(Concluded from page 92.)

producing organic compounds artificially, I will make one Before proceeding, however, to exemplify this power of or two further remarks upon their natural production. At present we are unable to trace the series of changes, undergone by carbonic acid and water, which result in the formation of tartaric acid, or sugar, or fat, or other complex vegetable product. It seems probable, however, that the process by which such bodies are formed does not consist in the simultaneous deoxidation of several atoms of carbonic acid into one complex molecule, as illustrated by the equation used in my last lecture to explain the production of mannite,

=

Manuite.

C6H1406;

Carbonic anhyd. Water. Oxygen. 6CO2 + 7H20 130 but that a series of more and more complex, less and less oxidised, intermediate bodies are successively formed, by the fixation of deoxidised carbonic acid upon the first-produced compounds. For example, we may conceive mannite to be built up somewhat in this manner. By a simultaneous dehydration and deoxidation of two molecules of carbonic acid, we should first obtain oxalic acid thus:— C2H ̧06 (H2O + 0) C2H204. Then by a further deoxidation of oxalic and carbonic acids, we might obtain tartaric acid, thus:

2 Carbonic acid.

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1 Oxalic acid

2 Carbonic acid

4 Oxygen

Tartaric acid

1 Oxalic acid.

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C2H2O4 C2H406

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The actual occurrence of these particular actions is quite unproven; but that some such actions take place is rendered highly probable by a variety of considerations. Thus, in the gradual development and ripening of the olive, we find certain vegetable acids replaced by mannite, and at a later stage the mannite itself replaced by the less oxidised and more complex oleine. Moreover, the compounds formed in one organ of a plant are known to be transferred, in a more or less altered form, to other organs, in which they become accumulated; and it is not impro

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