Obrazy na stronie

Fig. 3.

[ocr errors]
[ocr errors]

} Repulsion Resulting from Radiation.

187 Nov.3, 1876.

the radiation simply drove the balls apart, and immediately THE CHEMICAL NEWS. allowed them to come together again. When, however,

the beam was allowed to play upon the balls for about

half a minute they became warm and widely separated ; Vol. XXXIV. No. 884.

and upon now removing the beam of heat the balls did not fall together at once, but took several minutes to regain their original position. This experiment therefore proves Case I.

The bulb and contents being of the ordinary temperaON REPULSION RESULTING FROM ture, a spirit-flame was rapidly passed round the bulb to RADIATION.-PART II.*

warm it quickly on all sides. The balls were thus in the

condition imagined in Case II., being in a space warmer By WILLIAM CROOKES, F.R.S., &c.

than themselves. They immediately came together, (Continued from p. 176).

a touching c, and d touching b.

Many experiments were tried with the object of proving

experimentally the propositions in Cases III. and IV.; 90. Experiment proves the above reasoning to be correct, but with this apparatus it was found impossible to warm Á bulb-tube was prepared in the manner already described one of the balls without at the same time producing re(84), but in it were suspended, by separate silk fibres, two pulsion of the ball by the beam of radiation concentrated glass stems, each having pith balls at its extremity. upon it. There is, however, little doubt, from the experiFig. 3 shows the elevation and plan of the apparatus. mental proof of Cases I. and II., that the reasoning is The torsion of the silk fibres was so arranged that the equally correct in the other cases. pith balls a b hung freely about a millimetre from the 91. With a highly exhausted bulb and light pith index, balls c d. The glass stems were looped in the middle, which was found to be exceedingly sensitive to radiation, and bent so that they did not touch each other. After numerous experiments were tried to see if there was any complete exhaustion the following experiments were difference in action between the fingers and a tube of tried.

water of the same temperature. Many persons believe that there is a peculiar emanation or aura proceeding from the human hand, and Baron Von Reichenbach* considered that he had proved this to be the case. Were this true it was not impossible that the emanation would affect the pith index. I have been unable, however, to detect the slightest action exerted by my own or any other person's hand which I could not entirely explain by an action of heat.

92. A similar series of experiments were tried with various large crystals, which were presented in different ways and with various precautions to the pith index. At first a decided action was observed; but in proportion as precautions were taken to eliminate the effect of heat, so was the action seen to diminish, until very little doubt was left in my mind that the slight residual ađion would have been entirely stopped had it been possible, with the apparatus then used, to altogether eliminate the action of heat.

93. Attempts were made to see if chemical action would attract or repel the index. I could not, however, produce chemical action close to the exhaustel bulb, without at the same time liberating such an amount of heat as to mask any other action. .

94. Although I most frequently speak of repulsion by heat, and in illustrating any of the results obtained I genérally use either the fingers or the flame of a spirit-lamp as a convenient source of radiation, it must be clearly understood that these results are not confined to the heatingrays of the spectrum, but that any ray, from the ultra red to the ultra violet, will produce repulsion in a vacuum. I have already mentioned this fact in my first paper (58, 68). Experiments proving the similarity of action of all rays of the spectrum were shown before the Physical Society on June 20, 1874.7 They were, however, tried with a less perfect apparatus than the one I have since used for the same purpose, and need not be further alluded to till I describe the most ecent results obtained with the spectrum (110, 111).

95. Some experiments were tried with the object of ascertaining whether the attraction by heat, which, commencing at the neutral point (30 et seq.), increased with the density of the enclosed air, would be continued in the same ratio if the apparatus were filled with air above the atmospheric pressure.

Two bulbs containing ivory A beam of radiant heat was concentrated on to the two needles suspended by silk fibres were accordingly adjusted balls a c.

When applied momentarily and then removed to show the same sensitiveness to a hot body. One was A Paper communicated to the Royal Society, March 20, 1875. * "Researches on Magnetism, &c.,” translated by Dr. Gregory. From the Philosophical Transactions of the Royal Society of London, London, 1850. vol. clxv., pt. 2.

+ Phil. Mag., August, 1874.


Development of the Chemical Arts.


Nov. 3, 1876. kept for comparison, and the other was attached to an 8 litres, in which bromine and bromine-water collect. apparatus whereby the internal air-pressure could be into one of the lateral necks is fixed a movable glass artificially increased by a column of mercury. A little syphon, by means of which the bromine-water can be increase of pressure was enough to show that the sensi- drawn off into stoneware jugs. From the other neck a tiveness to radiation was greater; and under a pressure bent glass pipe passes down to the bottom of an iron of it atmosphere the superior delicacy of the ivory in the vessel, which widens upwards in a conical shape and dense air was very marked. Attempts to carry the pres- which is filled with water and iron turnings. Vapours of sure to higher points failed, owing to the bursting of the bromine which have not been condensed in the bottle are thin glass bulbs. With a little different arrangement no arrested by the iron. The impure chloriferous bromide of difficulty would be experienced in carrying the experi- | iron, as well as the bromine-water syphoned off are rements to a much higher point; but hitherto the greater turned to the stills for the next operation. interest attending the vacuum experiments has prevented At the beginning of the process scarcely anything but me from working further in this direction. My friend and bromine is evolved, afterwards chloride of bromine escapes, pupil, Mr. C. H. Gimingham, succeeded in the very diffi- and ultimately, when there is no more bromine in the cult feat of sealing up some of these tubes under an apparatus, pure chlorine is evolved. Dr. Frank, for the internal pressure of 1} atmosphere.

instruction of the author, kindly caused an operation to 96. To carry this experiment a step further bulbs con- be carried to the very end so that the three stages of the taining a suspended ivory or mica index were filled with process, which are easily distinguished by the colour of carbonic acid gas, water, carbonic disulphide, ether, the gas in the glass adaptor, were fully exhibited. In the alcohol, and other liquids. The index in carbonic acid ordinary routine of the works the operation is stopped behaved as if it were in air of somewhat higher density when the chloride of bromine begins to be given off. The than the atmosphere ; movements were also obtained workmen in these establishments receive in addition to when the liquids were present, but they were so obviously their wages a premium on the quantity of bromine obdue, in whole or in greater part, to currents, that they tained. Hence it is their interest to get through the proved nothing of importance.

greatest possible number of operations, and as the bro. (To be continued.)

mine lye is on hand in abundance they break off the operation as soon as the distillation of the bromine slackens. The quantity of sulphuric acid also is so cal

culated that it only just suffices for the liberation of the REPORT

bromine in a charge. Hence the bromine obtained ought

to be free from chlorine. It is found, however, in practice DEVELOPMENT OF THE CHEMICAL ARTS

that, on account, doubtless, of the imperfect mixture of

the reagents chloride of bromine is evolved even in the DURING THE LAST TEN YEARS.*

earlier stages of the distillation. The quantity of acid By Dr. A. W. HOFMANN.

(hydrochloric acid ?) must also be noticed which is given (Continued from p. 181.)

off towards the end of the process and produces such an evolution of hydrogen in the iron vessel that its contents

froth strongly. In order to prevent loss by running over Chlorine, Bromine, Iodine, and Fluorine.

a broad saucer-shaped rim is cast on the iron at the disBy Dr. E. Mylius, of Ludwigshafen.

tance of some centimetres from its upper margin in which The bromine lyes are kept in a large reservoir situate the overflow collects and is conducted away by a side above the stills, in which they can be preliminarily tube into a stoneware jug. heated by means of a coil of steam pipe. The height of Each operation takes up about two hours and yields the liquid is indicated by a float to which is attached a from 2 to 2'5 kilos. of bromine. The two bromine works cord passing over a pulley and supporting at its other at Stassfurt are so arranged that they are capable of pro. extremity a weight suspended in front of a scale, so that ducing 500 kilos. in twenty-four hours, but this quantity the workman in charging the stills is guided by the movehas never been actually furnished. ments of this weight.

(To be continued). The stone lid is closed by its own weight, but may be further loaded with extra weights ; the joints are made good with plastic clay. As we have already mentioned, the cover is raised by means of a counterpoise, but only THALLENE: ITS SOURCE, AND THE HISTORY when the apparatus is filled anew with manganese. The

OF ITS DISCOVERY. charge is about 4 cwts., which quantity serves for an entire series of operations. Not all qualities of manganese

By HENRY MORTON, Ph.D., are fit for this purpose, that of medium hardness being

President of the Stevens Institute of Technology. the most suitable. The charges of bromine liquor and of sulphuric acid are introduced through one of the small As the new hydrocarbon, thallene, which I succeeded in apertures in the stone cover, which is immediately after. isolating and investigating in 1872-3, is now being prowards closed with balls of clay held down by iron weights. duced on something approaching a commercial scale, As soon as the apparatus is thus suitably secured steam though in a very impure state, some points in reference to is turned on and bromine vapours immediately escape in its source, and the actual history of its discovery, may be abundance through the leaden tube cemented into the of interest at this time. second aperture in the cover. This leads to a worm sur. Petroleum is ordinarily distilled from first to last in two rounded with cold water in which the bromine is con

stages. densed. The original leaden worms have long ago been In the first place, it is heated in large stills until all replaced by a stoneware apparatus.

the lighter oils, consisting chiefly of benzin and the At first the excellent but very costly stoneware worms burning oils, are driven off, and there is then left a reof the English establishment "Lambeth Potteries," were siduum or petroleum tar, of a density of about 20°B. This used, but latterly German apparatus have been employed, residue or tar is then transferred to other stills, in many especially those furnished by the firm of Jannasch, in

cases run by other parties, and is again distilled for the Bernburg. The lower end of the stoneware worm opens production of lubricating oils and paraffin. by means of a bent glass adaptor into the central tubulure

At the end of this operation, when the bottom of the still of a large three-necked Woolff's bottle holding about is already red-hot and some coke has been formed, there *"

Berichte über die Entwickelung der Chemischen Industre runs very slowly from the condensor a thick yellow-brown Während des Letzten Jahrzehends."

tar, which is almost solid in cold weather, and in summer

II. 0:2750


[ocr errors]

II. 0*2750


On Thallene. Nov. 3, 1876.

189 only semi-fluid. Much of it seems to lodge permanently I of this new substance, which indicated that it was proin the heads of the stille, and my friend Prof. S. P. Lang- bably isomeric with anthracen. ley, of Pittsburgh, once secured me a barrel of it by A specimen of the same material was kindly conveyed having the still-heads blown out with steam.

by my friend Dr. H. C. Bolton, to Dr. Tiemann, of Berlin, This thick tar, prior to 1873, was only used as a lubri- who made two combustions of it with the following recant for the necks of rolls in rolling-mills, its great tena- sult :city securing its adherence under the very unfavourable I. O'2821 grm. thallene gave 0'1430 H20 5.63 p.c. H. conditions to which it was there exposed.

0'1412 H2O

5'70 p.c. H. About March, 1873, however, Mr. John Truax, of Pitts- I. O'2821

O‘9622 CO2 = 93.02 p.c. C. burgh, wrote me as follows, referring to this tar, a con

0.9384 CO2 = 93.06 p.c. C. siderable quantity of which he had before sent me from Anthracen requires-H, 5.62; C, 94.38. his own works :" Within a few months we have found a new use for it this subject, and hope to be able to give a rational formula

However, I by no means consider that I have exhausted in the manufacture of a lubricating oil, and we are trying for thallene before long. in every direction to obtain it. When we shall have our new works in order-in the course of a couple of months Stevens Institute of Technology in the Centennial Exhi,

Among the articles constituting the exhibit of the -we can let you have as many specimens as you want.”

It is this substance which contains thallene, and from bition at Philadelphia are the following preparations and which I extracted it. My attention was first drawn to it compounds of thallene :• in the following way:

I. Crude thallene washed with benzin. In the early part of 1872 I was engaged in the system

II. Crude thallene washed with benzin and hot atic examination of various fluorescent bodies, and one

alcohol. day in February Prof. E. N. Horsford calling upon me, I

III. Thallene purified by repeated crystallisations showed him some of these, and he then mentioned that he

from benzol. had brought from Pittsburgh a highly Auorescent tar, IV. Thallene as above re-crystallised from hot alcohol. which he would send to me.

V. Thallene chinone. Shortly afterwards about half an ounce of the yellow

VI. Thallene chloride. tar, enclosed in a bottle, was sent to me by Prof. Horsford

VII. Thallene bromide. from Cambridge. The bottle was broken in transit, and I

VIII. Thallene picrate. presume that part of the contents escaped. There was, IX. Sublimed thallene. however, enough for me to examine so far as to show that X. Solarised thallene. a solid crystallisable hydrocarbon could be extracted from Within the last few weeks I have received from Dr. H. the yellow tar. For convenience of reference I called this w. C. Tweddle (the same gentleman from whom I was “ viridine," from its green colour and fluorescence, and not able to procure any material with which to carry out made a preliminary note of it in a paper which I read be my investigations four years ago) a series of solid bodies, fore the American Institute in New York on March 29. to which he has given a variety of names, but which seem Wishing to carry my investigations further, I wrote to to consist simply of thallene in a greater or less state of Prof. Horsford for a further supply, and in answer re- purity. ceived the following note :

In the first place, under the name of petrozcene, he

“New York, March 2, 1872. sends me a quantity of the product obtained by washing "My Dear Sir,

thallene-tar with benzin or petroleum naphtha. This was “I am sorry the phial met with mishap. You might the first step of my process, published in 1872 (see Chem. obtain more from Dr. Herbert C. Tweddle, Pittsburgh, I News, vol. xxvi., p. 272), and, as might be expected, yields presume.

a product containing, it is true, some thallene, but con" The body that gives the fluorescence seems to me to taminated with a large amount of uncrystallisable tarry reside in the yellow semi-fluid substance. You will occa- matter and other impurities, which can be separated by sionally see streaks of green in it. I hope it may be use. washing with hot alcohol and repeated crystallisation ful to you in your investigations.

from solution in hot benzol (coal-tar naphtha) in the “I am, very truly yours, manner described by me at first.

"E. A. HORSFORD." Together with the above, Dr. Tweddle sends me a On receipt of the above letter I wrote at once to Dr.

series of products which he has obtained by distilling the Tweddle, describing the tar sent me by Prof. Horsford,

same, and separating from time to time what passed over, and he then and subsequenly promised to send me a quan

as the temperature of the still rose. tity, but never did so. In the meantime, my friend Dr.

The last but one of these products, which Dr. Tweddle G. F. Barker, then of New Haven, who had also brought

finds to have a melting-point of 460° F., which was the some of the same tar from the works of Mr. John Truax,

melting point found by me for thallene in 1872 (see of Pittsburgh, hearing of my destitution, sent me part of Chem. News, vol. xxvi., p. 274), appears to be a tolerably his specimen to see if my new body was in it, and on my pure specimen of thallene, yielding by two crystallisations finding that it was he wrote to Mr. Truax to send me a

from benzol a clear yellow substance characterised by the large quantity. This Mr. Truax did promptly, and on my

peculiar fluorescent spectrum and other physical properties further advising him how to purify it he sent me some by which this substance was first recognised. The other pounds of the new material, extracted from the tar as a

materials obtained at lower temperatures, prove to consist dark olive-green solid mass.

of thallene mixed with greater and greater amounts of the It was with the material so received by me from Mr. tarry substances and other matters which are removed by Truax that I made my investigations, already published, the process of crystallisation from hot benzol. Dr. which ended in establishing the individuality of a new

Tweddle's last or highest product seems to be a mixture hydrocarbon, resembling in many points anthracen, but of thallene with carbon and other matters, the result of a fusing at 460° F., and forming compounds with chlorine, partial decomposition caused by exposure to too high a bromine, oxygen, picric acid, &c., entirely unlike the cor- temperature. responding derivatives of anthracen.*

While it is interesting to find that by working on large Not having facilities in my own laboratory at that time quantities of a material a partial separation of thallene for such work, I was indebted to the kindness of my friend from other substances accompanying it may be effected, Dr. G. F. Barker, then of New Haven, for a combustion my observation of these products would not lead me to

recommend it as a desirable method of obtaining pure * See Chem. News, vol. xxvi., p. 272; Monit Scient,, vol. xv., p. 356; mer. Chem., vol. iii., p. 162; Phil. Map xlvi., p. 89; Poggen

thallene. Annalen, vol. clv., p. 551.

The best of the products sent me by Dr. Tweddle yielded


190 Practical Chemistry in the University of Virginia. { ,

Nov. 3, 1876. in benzol a dirtier and less pure solution than I obtained The deposition of free sulphur, doubtless as a result of from the material supplied me by Mr. Truax when that the reducing action at a low temperature of the stove-pipe had been well washed with benzin.

iron upon sulphur dioxide, is interesting; probably the Dr. Tweddle's material, according to his own description, reaction instead of Fe2+2S02=FeSO4+Fes, which was also washed with benzin before it was distilled, so occurs when the materials are more strongly heated, is that nothing was saved here, and evidently a considerable Fe+2S02=FeSO4+S. amount of the thallene must have been decomposed in the process of distillation. To obtain anything like a pure (6.) Analysis of the Ash of Hard Carbon Deposited in product crystallisation from hot benzol must, moreover, be Coal-Gas Retorts. By W. VAN SLOOTEN, of New resorted to at last.

Orleans, Louisiana. I have now on hand a large quantity of purified thallene The hard and heavy mass of carbon which encrusts the extracted from a barrel of the tar which was secured for inside of a gas retort for some time in use, and which me by the kind exertions of my friend Prof. S. P. Langley, results from the decomposition of volatile hydrocarbons of the Allegheny Observatory, and with this I am con- | produced during the distillation, forms an admirable fuel ducing a thorough investigation of its chemical properties for laboratory furnaces, in which a very high temperature and derivatives.

is to be attained, this use having been first suggested by Violette (Comptes Rendus, October 28, 1872, p. 1028).

Its value depends partly upon its high density, but chiefly NOTES OF WORK BY STUDENTS OF upon the small quantity of ash which it leaves when PRACTICAL CHEMISTRY

burned, so that the intervals between the fragments of

fuel do not become choked nor the draught of air obLABORATORY OF THE UNIVERSITY OF

structed. Mr. van Slooten undertook to determine the

amount of ash in specimens of this carbon taken from a VIRGINIA.

lot of several tons obtained from the gas works of RichNo. V.

mond, Virginia. Communicated by J. W. MALLET,

Small fragments of the material were burned in a Professor of General and Applied Chemistry in the University. stream of oxygen gas, supporting them on platinum foil (Concluded from p. 180.)

in a hard glass tube. The combustion was not very easy

to manage, since too slow a supply of oxygen readily led (5.) Analysis of a Stove-Pipe Deposit. By S. D. Cren

to the dense carbon ceasing to glow, while a little faster SHAW, of Orange Co., Virginia.

stream swept away the light particles of ash. It soon

appeared that different layers of the deposit varied conIn one of the working rooms of the Laboratory a“ base, siderably in the amount of ash. Thus three specimens burning” stone, burning Pennsylvania anthracite and fed

gaveby gravity from a central hopper, is kept alight during the

No. I

1.66 per cent whole winter both by day and night. The stove-pipe, of

No. 2

0:35 common Russia sheet iron, rises about 12 feet vertically,

0'95 and then runs horizontally about 24 feet before entering the chimney, When, in cold weather, the fire is burning while another sample, dull and earthy in appearance, slowly and draughts of cold air are allowed to enter the from the gas works of Charlottesville, Va, gaveroom from the doors, some of the products of combustion

3*77 per cent are condensed and come to the outside of the pipe at the The ash from this last was analysed, it having proved joints, running slowly down the outside as a thick, orange excessively tedious to get enough of either of the others. yellow, liquid mass in little streams of } to } inch wide. The results were :-In the course of three or four days such a deposit hardens


42'00 into an opaque mass of light brownish yellow colour.

47'00 Qualitative examination proved that this consisted

Na20 essentially of ammonium sulphate and free sulphur, with


trace small quantities of ferraus sulphate, free sulphuric acid,


372 and a hydrocarbon apparently of one of the higher series. A portion of the material was completely oxidised and the total sulphur determined as barium sulphate ; the

10129 amount of barium sulphate yielded by another (unoxidised)

Deduct O equiv. to CI 0.84 portion treated merely with water was also ascertained, and the difference gave the means of calculating the free

100'45 sulphur. Ammonia was determined in the cold by The trace of lithium was detected by the spearoscope in Schlösing's method. It was ascertained that the iron the flame of the furnace. was present altogether as a ferrous salt; it was then fully

The immunity from clinker or accumulation of ash in oxidised and determined as Fe2O3. 'The carbon and the furnace is seen to be due not always to the existence total hydrogen (there being also nitrogen and sulphur of a very small proportion of mineral matter in the fuel, preseri) were determined by combustion with cupric oxide but also to the very light condition in which this separates aided by a small amount of potassium chlorate, and the and is swept up the chimney with the draught. The gases were passed over heated lead chromate and re

occurrence in some cases of so considerable an amount of duced copper turnings respectively. The oxygen of the the not readily volatilisable elements silicon and iron in water was obtained by difference. The results were :

this retort carbon is not very easy to explain, and rather (NH4)2SO,


suggests the mechanical carrying forward of solid particles 3.73

with even the comparatively gentle rush of combustible H2SO4


gas escaping from the coal. S

735 с


(7.) Production of Metallic Zinc free from Iron and H comb. with

Carbon, for Analytical Use. By R. D. BOHANNON, ci

of Mathews Co., Virginia. Si02

On the whole, metallic zinc is the most convenient H20

material for reducing ferric to ferrous sulphate in the often recurring volumetric determination of iron by potassium permanganate. For this purpose we must have the metal

No. 3





O'II trace 012



Nov. 3, 1876.
Anthracen Testing.

191 perfectly free from iron and carbon, a condition in which not to give a blue reaction with the molybdic test, owing it is almost impossible to procure it in commerce, even to the minute quantities of volatile oils and other impuri. from the professed dealers in pure chemicals, while the ties they contain.” I think I shall be able to show that purification by distilling out of contact of anything which this blue reaction is due simply to the presence of alcohol, can yield either of the elements to be removed is not an and not to volatile oils or similar impurities. In the first easy or convenient laboratory process. It is true that place, I examined a sample of the ordinary unreduced zinc containing iron might be used if the amount of the chloroform prepared from ethylic alcohol by Messrs. J. F. latter were certainly known, and known to be uniform, Macfarlan and Co., and found that it gave no trace of blue but this can scarcely be depended on. Mr. Bohannon has coloration with the molybdic test, while the reduced tried the production of the pure metal from the chloride i chloroform (sp. gr. 1.496) gave the characteristic alcohol (free from iron) by means of sodium, and with fairly satis- reaction at once. I next procured some of the volatile factory results.

oil obtained in the purification of chloroform, and treated Commercial zinc was dissolved in crude hydrochloric it repeatedly with solution of calcic chloride, to remove acid, the solution diluted, and sulphuretted hydrogen the alcohol. When a drop of this oil was added to the passed through to saturation. The clear liquid was molybdic solution a pinkish tint was developed, but no blue filtered off from the precipitate of lead sulphide, &c., after coloration. I then mixed a drop of the purified oil with standing for twenty-four hours, heated to the boiling- 1 drachm of pure chloroform, and submitted the badly. point, and treated with nitric acid enough to peroxidise smelling mixture to the molybdic test, with the result that all the iron present, which was then precipitated by the no colour whatever was produced. addition of ammonia until a portion of the zinc had been I trust that I have said sufficient to prove that Dr. thrown down. After again standing for twenty-four hours, Davy's strictures on the character of commercial chlorothe solution was filtered off, evaporated to dryness, and form are unwarranted, and that the impurity he has discothe fused zinc chloride broken into small fragments. vered is simply alcohol, which is not an impurity in the These were mixed with bits of metallic sodium and thrown correct sense of the word. into a previously heated and clean earthen crucible. The

93, Abbey Hill, Edinburgh. reaction was so violent that most of the zinc was volati. lised and lost, but it was found that this could be prevented by previously diluting the fused zinc chloride either with sodium chloride or zinc oxide to a moderate

ON ANTHRACENE TESTING. extent. The metal obtained was quite free from iron

By DR. FREDERICK VERSMANN. (and of course from lead, copper, &c.) but afforded a trace

(Continued from page 179). of carbon derived from a little naphtha still adherent to the fragments of sodium used. This is easily prevented by careful drying of the larger pieces with a cloth, and then I am fully aware of the objections likely to be raised cutting off the outside crust. As regards the yield, to my test. It will be said some confusion will arise in I'9 ozs. of pure zinc was obtained with an expenditure of consequence, because the standard of valuation will be 20 ozs. of sodium, but it was found necessary to have changed, inasmuch as my test will always indicate a lower much more zinc chloride present (as a protective covering percentage than the one now in use. My answer is—My from the air) than the sodium was capable of reducing. test is more correct and more trustworthy; and at all University of Virginia,

events the buyers of anthracene are fully aware that the August 28, 1876.

present quinone test does not give them the true value of the article, but only an indication, which they supplement themselves by further analysis.

The history of anthracene testing has been gradually NOTE ON DR. DAVY'S TEST FOR THE PURITY progressive, from the alcohol the bisulphide of carbon, OF CHLOROFORM.

and thence to the quinone test. Each of these modifica

tions reduced the percentage, and was accompanied by By DAVID B. DOTT.

an increase in the price of per cent, and if my test should

be adopted the enhanced value of per cent will soon be In the Chemical News (vol. xxxiv., p. 137) appears an regulated and find its level. interesting and valuable paper on a "New Chemical Test In looking at the first table it will be noticed that for Alcohol,” by Dr. E. W. Davy. In that contribution, although the results found by the usual test range from however, there are some remarks of a misleading nature. 114 to 68.5 per cent, and that of the crystals from 6:6 to which I think ought not to be allowed to pass without 63-2 per cent, the percentage of the powder Auctuates correction. The first statement to which I would take within very narrow limits. Omitting Nos. 2, 12, 28 on the exception is the following :—“As regards chloroform, one one hand, and Nos. 9, 12, 26 on the other hand, the reof its common impurities is ethylic alcohol, which it may maining 24 samples yield between 4 and 6 per cent of contain either from imperfect preparation or from fraudu- powder. lent addition, the very high price of chloroform offering a I have been very particular, as far as possible, to learn great temptation to the unscrupulous vendor to increase the history of all these samples, and I can fully account its bulk or weight by the addition of alcohol." Now, it is for the exceptionally low and high percentage in powder manifest that as the specific gravity of pure chloroform is of the six samples; hence I am justified in neglecting them at least 1'500, while the British Pharmacopoeia gives 1.490 in the following considerations :as its standard specific gravity, the official chloroform The observation that a sample of the lowest quality must of necessity contain alcohol. It is therefore alto yields nearly as much powder as another of the best gether erroneous to assert that the alcohol is present quality, which last shows six times the amount of quinone either " through imperfect preparation or fraudulent addi- by the usual test, is a strong confirmation of the welltion, the real reason for its addition being the prevention known practical experience that the low per cent article of decomposition in the chloroform. It appears that this is always of less comparative value than a better quality new test can detect the presence of 1 part of spirit in article. 1000 parts of chloroform ; but as the addition of 1 part of Although this fact is well understood, it is but little spirit to 2000 parts of chloroform reduces the gravity by acted upon, or the many low-quality lots would long about o‘001, the specific gravity would seem to be a more have disappeared from the market. I think if the manudelicate test of the presence of alcohol than is molybdic facturer can be clearly shown that a better quality article acid. Dr. Davy informs us that “ he was unable to obtain is more profitable he will after all improve his make, and any sample of chloroform in commerce sufficiently pure as the buyers will take it all the more readily, I shall be

« PoprzedniaDalej »