NEWS

interest.

The present year will be fraught with interest to the chemist and druggist. A national Pharmacopoeia is about to appear of more important a character than any which has issued from the College of Physicians. This work will receive our earliest attention. Again, the rights of chemists and druggists are seriously threatened; and it will be necessary for the majority to combine in order to defeat any attempt of the Medical Council to deprive them of their privileges, as well as to secure the exemption from serving on juries, which has already been conceded to a section. To promote these objects we shall render every possible aid.

The thorough organisation of the trade should be completed as early as possible, and the machinery is fortunately ready by which this can be effected. The United Society of Chemists and Druggists offers the means by which the entire body may operate in concert. We say this in no spirit of opposition to the Pharmaceutical Society. That society voluntarily closed its doors to the majority of the trade some years ago, and now can be in nowise astonished that, at the present crisis, some other organisation should be found necessary.

But it must never be forgotten that the occupation of a chemist and druggist has a scientific as well as a commercial aspect; and we are glad to have the opportunity of recommending to our readers an organisation which has for its object "the encouragement of pharmaceutical research." The British Pharmaceutical Conference offers the means by which every one who will interest himself in the improvement of pharmacy can be brought into communication with others similarly disposed, so that all may work in concert for the common good. We heartily commend the Conference to the notice of our readers. It has been organised on a thoroughly catholic VOL. IX. No. 213.-JANUARY 2, 1864.

basis, and has for its sole object the promotion of knowledge.

In conclusion, we may add that it is our intention to publish occasional courses of lectures, and popular papers, on different branches of the science; and it is to be hoped that our more recondite readers will look with favour on these attempts to diffuse more generally a knowledge of chemistry, and so, we hope, stimulate a desire for a more profound acquaintance.

SCIENTIFIC AND ANALYTICAL CHEMISTRY.

Contributions to the History of Thallium,

by WILLIAM CROOKES, F.R.S.

The

Oxalate of Thallium.—This salt is readily prepared by boiling together equivalent quantities of carbonate of thallium and oxalic acid, in just sufficient water to dissolve the product when hot. Upon cooling, oxalate of thallium crystallises out in the form of small prisms, brilliantly white and lustrous. It is not very soluble in water, and is insoluble in alcohol. One hundred parts of boiling water dissolve 9.031 parts of the salt; and the same quantity of water at 60° F. dissolve 1'443 parts. One part of the oxalate, therefore, requires 1107 parts of boiling water, and 69.27 parts of cold water to dissolve it. M. Kuhlmann has ascribed to the neutral oxalate of thallium the somewhat improbable formula, CTIO; but several closely concordant analyses have shown me that this salt has the normal constitution of neutral oxalates. method adopted for analysis is very simple, and gives remarkably accurate results. A weighed quantity, which had been dried over sulphuric acid, was gradually heated in an air bath to an increasing temperature, the trace of hygroscopic moisture was driven off, and the weight being taken from time to time. At 230° F. a oxalate then bore a temperature of 400° F. without further change. At 480° F. it began to discolour slightly, but it was found to have lost scarcely any appreciable weight. Pure concentrated hydrochloric acid was afterand in a few minutes they were converted into a porous, wards poured over the crystals; slight heat was evolved, evaporated off over a water bath, and the residue was spongy mass of chloride. The excess of acid was acid was then poured on, and the evaporation and heating heated to 400° F. for ten minutes. More hydrochloric of weight took place, the final heating being in an air were repeated. This was performed until no alteration bath at 500° F. As oxalic acid is entirely dissipated by exposure to a temperature of 320° I., the above treatment effectually removes this acid. Many experiments have satisfied me that chloride of thallium will bear a temperature of 500° F. without any loss of weight; at a slight increase of heat the chloride sudsimultanecuely evolved. denly fuses to a thin brown liquid, white vapours being

following pertentages of metal in this salt:Analyses conducted in the above manner gave the

82.298

Binoxalate of Thallium.-Upon mixing together two equivalents of oxalic acid to one of carbonate of thallium, and boiling, the binoxalate is deposited, on cooling, in the form of large plates, having a pearly lustre. The crystals were purified and analysed in the same way as the neutral oxalate. Upon exposure for 1 hours to a temperature of 270° F., the crystals became opaque, and were found to have lost 3.61 per cent. of water. Further heating did not increase this loss. The percentage of thallium in this dried salt was found to be 69'341. The formula CHTIO, requires 69.520 per cent. of metal.

The amount of water present in the crystallised binoxalate did not correspond in my analyses to a definite number of equivalents. The mean percentage obtained was 3.61. One equivalent of water in the binoxalate would require a loss of 2'99 per cent., whilst two equivalents of water would correspond to 5'80 per cent. The method of analysis was such as to render the probable error of manipulation insignificant; and the closely concordant results obtained in the estimating the thallium in the dried salt prove that the error was in the amount of water originally possessed by the binoxalate when taken for analysis. It had been dried for thirty-six hours over sulphuric acid, and it is not unlikely that it may have slightly effloresced. An estimation of the water of crystallisation, in a specimen taken out of the mother liquor, and merely dried by pressure between blotting paper (containing, therefore, a little free moisture), gave results corresponding to a little more than two equivalents of water. I am, therefore, justified in assuming that the formula for the crystallised binoxalate of thallium is

Separation from Rubidium.-Bunsen* has made further investigations on this rare element. He could not apply Allen's method to the preparation of pure caesium compounds because of the small quantity of the element obtainable from the sources at his command. He discovered that cæsium could be separated from rubidium by another plan, which is as follows:-In a mixture of pure RbCl and CsCl the Cl is determined, and from its amount that of Rb is calculated. The chlorids are converted into carbonates, and to the latter salts a little more tartaric acid is added than is necessary to produce neutral tartrate of cæsium and bitartrate of rubidium. The mixture dried and pulverised is brought upon a funnel, whose neck is stopped by a small filter, and the whole is placed in an dtnrosphere saturated with moisture. The neutral caesium salt deriquesces, and passes the filter, while the acid' fubidium-salt remains

behind.

Equivalent. The caesium tartrate was converted into chlorid, and the latter was purified from traces of KO and LiO, which it acquired from the tartaric acid, by conversion into platin-chlorid, washing, &c. This operation was repeated six times, the salt being each time analysed. The last three results coincided very closely, and, from their average, the equivalent 132.99

Pogg. Ann., cxix., 1.

was deduced, which agrees with the number obtained by Johnson and Allen, viz., 133'03, and fully authorises the use of the round number, 133, as expressing the combining proportional of this element.

Deliquescence of CSCI.—Bunsen further maintains the accuracy of his original assertion that CsCl is deliquescent. Johnson and Allent had stated that it was "not only not deliquescent, but scarcely hygroscopic." The observations of both are entirely correct for the circumstances under which they were made. We have since observed pure CsCl to deliquesce in a few moments on an August day; while at this writing, September 24, the same specimen has been exposed all night to the air in a room with open windows, temperature 55° F., and is in appearance perfectly dry. Bunsen rightly remarks that "Johnson and Allen appear to have made their experiments in a comparatively dry atmosphere, in which, as is known, many deliquescent salts are unaltered, and, therefore, overlooked the deliquescent character of CsCl." The experiments of Johnson and Allen were made in the cloudy and foggy, but cold weather of November,-weather which is commonly designated as damp, but the real moistness of the atmosphere they only judged of from sensation.

CsCl much resembles urea in its hygroscopic relations, The latter substance is stated by most recent authors, including those who have had occasion to observe it especially, to be unaltered in the air. Thus Lehmann, "Physiological Chemistry;" Gorup Besanez, "Zoochemische Analyse;" Mitscherlich, "Lehrbuch; " Gerhardt, on authority of Pelouze, "Traité de Chimie Organique;" and Neubauer, "Analyse des Harns," assert that it is unchanged by exposure to the air. Gorup Besanez, "Lehrbuch der Physiologischen Chemie," 1862, states that it is "permanent in the air, but rapidly absorbs moisture." Gmelin mentions that "according to earlier statements it deliquesces in moist air." We have repeatedly observed that in very moist air urea rapidly deliquesces, though usually, except in summer weather, it is not visibly affected by atmospheric moisture.

Spectrum of Casium.-Johnson and Allen, in the paper above referred to, observed that "Kirchhoff and Bunsen, in the figure given by them (Pogg. Ann.. 1861, and Fres. Zeitschrift für Analyt. Chemie, Heft 1, 1862), represent eleven lines. We find without difficulty seven more lines, and observe further that some of those figured by Kirchhoff and Bunsen are not mapped in their correct position."

In relation to this, Bunsen remarks, " We regret that Messrs. Johnson and Allen appear to have neglected to make an accurate comparison of their spectrum with ours, otherwise they would have easily convinced themselves that the lines given by them agree with ours as closely as is possible; that, on the other hand, three lines are figured on our plate which do not occur at all in the cæsium spectrum. These lines have been printed on a number of lithographs by fault of the lithographer, in consequence of a misunderstood proof that was not sent to us for revision, and lie near and to the right of the lines designated by Johnson and Allen as VI., X., and XV."

Johnson and Allen could but conclude that the coloured plate in Poggendorff's Ann., accompanying the paper of Kirchhoff and Bunsen, was a copy of their spectrum as far as the important, ie., the characteristic and brilliant lines were concerned. They are therefore scarcely more in fault in having "neglected to make an accurate comparison" than Kirchhoff and Bunsen are in permitting incorrect spectrum plates to be circulated. Fresenius

† CHEMICAL NEws, vol. vii., p. 110,