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58

On the Formation of the Topaz and the Zircon.

By passing fluoride of silicium over calcined alumina placed in a porcelain tube and heated to whiteness, the whole is converted into staurotide; fluoride of aluminium is disengaged, which may be collected, and which is identical with that I prepared after obtaining crystallised silicium (silicium diamond). This staurotide, which is in right rhomboidal prisms, resembles natural staurotide in form and optical properties. Their composition is identical, as my analyses prove,

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and ought to be represented by the mineralogic formula SIAL. It contains no trace of fluorine.

This circumstance led me to make the following experiment:-Into a porcelain tube, placed vertically, I put alternate and cylindrical layers of alumina and quartz, commencing with alumina, and finishing with quartz, and through this pile, when heated to white heat, I passed a current of fluoride of silicium. The layer of alumina became transformed into staurotide (SIA), with production of fluoride of aluminium, which was entirely absorbed either by the quartz or silica. By this means the same staurotide (SiAl2) is obtained, and the fluoride of silicium regenerated, and so on; the alumina and the quartz both being changed into the same crystallised matter, staurotide, of which I have given the analyses. As the last layer is composed of quartz, and as no trace of fluorine remains in the contents of the porcelain tube, it follows that after all these transformations the identical quantity of fluoride of silicium issued from my apparatus as entered it; a fact which is besides easily proved by experiment. Thus, fluorine itself, without becoming fixed, served to combine two substances the most fixed and most difficult to enter into combination-silica and alumina. Thus, a very small quantity of fluorine is required to transform into staurotide or to mineralize indefinite quantities of silica and alumina.

My analyses, which very nearly confirm those of M. Forchhammer, give for the composition for topaz the following numbers, which have reference to the least volatile elements of this mineral:

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At first sight it appears that it is possible to form this singular substance by the action of fluoride of silicum on alumina, under the above circumstances; but in my experiments I have never found any substance resembling topaz. Moreover, it Brazilian topaz is put in a current of fluoride of silicium in contact with alumina, which becomes transformed into staurotide, the topaz entirely decomposes, losing 22 per cent. of its

It is advisable to introduce into this porcelain tube another tube

of gas carbon, and to put the alumina also in carbon boats. (See the description of this apparatus in the Annales de Chimie et de Physique, Third Series, vol. xlvi. p. 194).

2 This staurotide, obtained by both M. Caron and myself (ComptesRendus, vol. xlvi. p. 764), must not be confounded with natural

staurotide, which, containing always a large proportion of iron, I have never succeeded in producing by this process. I have even some doubts as to the identity of their crystalline forms. By-and-bye I shall revert to this interesting question in natural philosophy.

3830 Annales de Chimie et de Physique, vol. xlix. "Memoirs on Bilicium and the Metallic Sesquifluorides."

{CHEMICAL NEWS,

Feb. 1, 1862.

weight. This experiment clearly proves that topaz cannot be reproduced in our laboratories, nor be naturally formed by the contact of alum and fluoride of silicium at a high temperature.

Topaz must be formed by the wet way. This is proved by Dr. Brewster's observations on the liquids which it contains, and by the results of my own analyses,* in which I estimated a volatile matter which I considered to be water; but according to M. Lervy it is ar. organic matter, and a nitrogenised organic matter according to M. Delesse. To these observations let me connect a remark to which I attach some importance. I have found vanadium in a great many hydrated aluminous matters, particularly in the Gibbsite of Baux. I have also found it in topaz which I believe came from Brazil; and this characteristic, common to many substances which decompose or are transformed by the action of fire, appears to me to indicate the intervention of water in the formation of minerals which contain vanadium. I hazard the hypothesis that it is decidedly from the hydro-fluo-aluminic acids which I have described in a recent memoir that topaz may be most easily derived. Chondrodite, humite, or even lime and magnesia silicates cannot be formed under the influence of fluoride of silicium, for the magnesia or lime when heated in this gas are changed into vitreous or crystalline matters with a composition bearing no relation to veins of minerals and metamorphic earths. The following shows the composition of these substances, formed atomically in the most simple manner. Their formulæ, given in the following hypothesis, clearly shows their formation :Silica. Magnesia Magnesium Fluorine (by loss).

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With glucina, which, like alumina, yields a volatile fluoride, I hope to obtain phenatite. By passing fluoride of silicium at red-white heat over glucina, I obtained, besides fluoride of glucinium, some beautiful crystals which I have not yet measured, and which I can identify with no known mineral, for they have given the following results:

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Thus fluoride of silicium yields by the dry way no known earthy mineral; but this is not the case with a substance found in volcanic earths-zircon-which is produced in the most beautiful forms by passing fluoride of silicium over zirconia. The octahedral crystals thus obtained, which I have measured, are exactly analogous to the zircons of Somma (Vesuvius). They have the same facettes, the same angles, the same external appearance; and it is almost absolutely certain that they were formed under the influence of fire. Here again it is evident that fluorine in small quantities present in

"On the composition of volatile substances in natural silicates." (Lithographed lessons on mineralogical analysis, given at L'Ecole Normale.)

metamorphic earths of this kind has been sufficient to produce indefinite quantities of zircon.

If, in fact, alternate layers of zirconia and quartz are placed in a porcelain tube, the first layer being of zirconia and the last of quartz, the zirconia by contact with fluoride of silicium is transformed into zircon and volatile fluoride of zirconium, which encountering the quartz converts it into zircon and fluoride of silicium, &c. Finally, the mineralisation extends throughout the porcelain tube, and exactly the same quantity of fluoride of silicium issues from as entered the tube. No portion of the fluorine becomes fixed.- Comptes-Rendus.

of acid papers for Seidlitz powders, evidence of corrosion
or chemical action, and the presence of lead was shown
by the resulting compound blackening in the presence
| of HS.

For simply detecting the presence of the lead, I found the readiest method to consist in oxidising the foil with nitric acid, and to dissolve out the nitrate of lead from the insoluble peroxide of tin with hot water. Crystals of the salt were generally deposited from the solution on standing. For the quantitative estimation of the two metals, I have tried several processes, with varied degrees of success.

First, dry chlorine gas was passed over the foil, heated in a bulb tube, when the volatile bichloride of tin distilled over, leaving the fixed chloride of lead in the bulb. On the Adulteration of Tin Foil, by J. H. BALDOCK. This process was not however, adopted, for two reasons: HAVING occasion, a short time back, to prepare some 1st, because some difficulty was experienced in condenscompounds of tin, I employed for the purpose, in the ing the whole of the distillate; 2ndly, and most imabsence of granulated metal, some tin foil, and was sur-portant, that some of the foil at the termination of the prised to find my product very largely contaminated process fused and escaped the action of the gas. with some other metal. Upon careful examination of the tin foil which I had used, I found it to contain a large amount of lead. Believing that the presence of this metal in such considerable quantity in the foil is not generally known and recognised, I obtained a number of specimens of commercial foil and submitted them to analysis. Some of these were kindly supplied to me by Mr. Haselden, of Conduit Street, the remainder being collected by myself. They consisted of,-. Ordinary commercial foil; 2. Embossed foil; 3. Tinned paper; and 4. Foil lining the packets of Horniman's tea; together with a sample of "pure tin foil," from Mr. Saddington's, and some of Betts' patent capsules. The following table of the results of the analysis in the several cases will show the proportion of lead and tin present in the different samples. The processes employed will be subsequently described.

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It thus appears that tin foil is such only in name, though the reason of this large admixture of lead is not very apparent, because the so-called pare foil noticed above, which contains a much smaller proportion of lead, appears to be in every respect better suited to general requirements, being at once thinner, lighter, and tougher. The only cause that I can assign is, that the alloy may be more easily rolled than the pure metal. I may remark that the specific gravity of the alloy is less than would be indicated by calculation from the specific gravity of the two metals. In Gmelin's Work a table is given showing the actual and calculated specific gravitics of these two metals when alloyed in different proportions.

Not long since there was a great deal said respecting the packing of tea, tobacco, snuff, &c., in lead foil, as in several instances accidents had occurred, owing, as it was then shown, to the formation of a sub-carbonate of lead, which was disseminated through the contents of the packet; and, if I recollect rightly, it was suggested that tin foil should be substituted for that made from lead. If it is true, however, that tin foil is itself so extensively adulterated with lead, it is obvious that no advantage would be gained. On the contrary, such an alloy is more easily acted upon than either of its components would be alone. Some time back I noticed on some foil, which had been in contact for some time with a packet

Secondly, the foil was treated with nitric acid, specific gravity 137, whereby the tin became converted into the insoluble binoxide, and the lead into nitrate; the latter was dissolved out by water, the lead precipitated as sulphate, which was washed, dried, and calcined, and from which was calculated the amount of the metallic lead; the binoxide of tin was also washed, dried, and calcined, and the amount of metalic tin calculated from it; this process is simple, expeditious, and appears to give very good results.

Thirdly, the foil was treated with nitric acid, and evaporated nearly to dryness, with a small excess of sulphuric acid, whereby the two metals were converted into sulphates; the nearly dry residue was then washed with water, and digested repeatedly with solution of acetate of ammonia of specific gravity 106 or above, which dissolved out the whole of the sulphate of lead. Sulphide of ammonium was added to the solution, and the precipitated sulphide of lead washed and re-converted into sulphate by heating with a mixture of nitric and sulphuric acids, and from this the metallic lead was calculated as before: the sulphate of tin was then calcined to convert it into binoxide, from which the metallic tin was calculated. There appears to be no objection to this process, except that it is rather long, as it gives very good and accurate results; it has, moreover, the merit of simplicity. The annexed table gives at A the results of the second process upon sample No. 1; and at B the results of the third process upon the same sample :

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Both these, it will be observed, estimate the lead a little too low, arising from insufficiency of washing, some time being required to complete that part of the process.

The process, however, which I found to give me by far the best results, and to be the most convenient in execution, is one described by Rosé. It consists in fusing the alloy with an excess of a mixture of sulphur and carbonate of soda. The metals combine with the sulphur to form sulphides, while at the same time the sulphur and carbonate of soda react to form sulphide of sodium. The sulphide of tin combines with the alkaline sulphide, forming a soluble compound, while the sulphide of lead remains unaffected. The fused mass is digested with water, and filtered. The insoluble sulphide of lead is

60

On the Preparation of Picramic Acid.

(CHEMICAL NEWS,

Feb. 1, 1862.

A small quantity of hypochlorous acid does not sensibly alter the colour of the solution; but a large quantity changes it to orange, then to yellow, and finally the colour disappears.

washed, dried, and calcined with a mixture of nitric and
sulphuric acids, whereby it is converted into sulphate,
from which the lead is calculated as in the previous
cases; to the filtrate excess of hydrochloric acid is
added, which decomposes the sulphur compounds, and
precipitates sulphur and the sulphide of tin; the pre-liquid.
cipitate is washed, dried, treated with nitric acid, and
calcined, when binoxide of tin results, from which the
metal is calculated.-Pharmaceutical Journal.

:

On the Preparation of Picramic Acid. WE are generally directed to dissolve picrate of ammonia in alcohol, saturate with ammonia, and then with sulphydric acid. These saturations are tedious and troublesome, and as picrate of ammonia is but sparingly soluble in alcohol, much of the latter is consumed, and the solutions are very bulky. The following process will be found greatly preferable :Picric acid (which is very soluble in strong alcohol) is dissolved in cold alcohol, and excess of sulphydrate of ammonia added. The liquid then only requires to be evaporated over the water bath, the residue to be exhausted with boiling water, filtered, and treated with acetic acid. The picramic acid obtained in this way is very pure, and the quantity large. In one experiment, were the quantities were weighed, over 63 per cent. of the weight of the picric acid consumed was obtained. If too little sulphydrate be used, picric acid remains in the mother water, from which the picramic acid crystallises, and may be recovered by precipitating with carbonate of potash.-American Journal of Science,

No. 95.

TECHNICAL CHEMISTRY.

On the Reduction of Binotronaphthaline by Sulphuric Acid and Zinc, by M. E. JAQUEMIN.

Potash and ammonia dissolve it, forming a purple Notwithstanding this apparently similar reaction, it is impossible to confound it with alizarine; for by adding alum to this alkaline liquid, I obtained a violet lake; while alizarine, dissolved in an alkali and treated by a salt of alum, produces a red lake.

By combining this new colouring principle with zinc, stannous, stannic, and mercuric oxides, I have produced violet lakes, with more or less blue in them.

An alcoholic solution of the colouring matter, diluted with twice its volume of water, is made opaline by acetate of lead; the addition of a few drops of carbonate of soda forms a violet-blue precipitate. Basic acetate of lead forms an opaque blue in a similar solution, from which carbonate of soda produces a clear blue-violet precipitate. I have obtained a brown lake with ferric oxide, violetbrown with ferrous oxide, and red-brown with cupric acid.

The facts I have stated will suffice, in the absence of a closer examination, to characterise this colouring principle, and to differentiate it, not only from alizarine, but from every other colouring matter. To ensure conviction, I prepared two symmetrical specimens mordanted with alum and iron. One I dyed with madder in the ordinary way, the alum mordant in red, the iron mordant in violet; the other, on the contrary, dyed with the colour obtained by reducing binitronaphthaline, is coloured in an entirely different way,-the alum mordant became violet, and the iron mordant grey.

The violets and greys appear to be very fast on cotton; for they resist soap and concentrated acetic acid. I have not yet had time to discover what influence light has upon them. Whatever it may be, I believe this new body will be of great service in dyeing and printing stuffs.- Comptes Rendus.

BUT little convinced, d priori, of the possibility of transforming binitronaphthaline into alizarine-which would On the Colouring Matters Derived from Naphthaline, constitute a singular anomaly,-I felt I ought to repeat M. Roussin's experiment. The results I have arrived at are entirely opposed to the facts announced by M.

Dumas.

I have three times treated binitronaphthaline by commercial sulphuric acid and zinc, at the temperature and for the length of time indicated by M. Roussin, carefully following the stages of the reaction, collecting separately the chief part of the colouring matter, and urging the reducing action to the highest point with the last portion. After having diluted it with about eight times its volume of water, and then boiled it, I let it cool, and threw it on a filter. The liquid which passed, was of a beautiful violet-red colour; this could not be alizarine, as this is entirely insoluble in water charged with sulphuric acid.

By washing the precipitate with distilled water, the liquid passes coloured so long as there is acidity. The insoluble portion in the pure water, dissolved in alcohol, to which it gave a violet-red colour; now alizarine, dissolved in alcohol, takes a yellow colour. A black carbonaceous residue remained.

The new colouring matter is soluble in ether, to which it imparts a violet-red tinge; while alizarine gives it a golden yellow colour.

by M. SHEUERER-Kestner.

M. RoUSSIN's recent works, as well as a paper sent by M. du Wildes to the Chemical Society, have determined me to send the following paper to the Academy, which is a copy of a sealed packet deposited by me in the records of the Industrial Society at Mulhouse, on November 15, 1860.

The specimen of silk I exhibit was dyed with the colouring matter obtained by treating naphthylamine at 200° by dry nitrate of mercury. The matter is more or less red according to the quantity of metallic salt and degree of heat employed. The shade may thus be varied, from a slight tint of ordinary aniline violet to the colour of fuchsine. The nitrate of mercury may be replaced by bichloride of tin, and generally by the other bodies which are used to produce aniline reds and violets. These methods of preparation have been taken from the works on Organic Chemistry, in which they are partially described; for example, I quote the principal passages from these works:

1. "Naphthylamine, when treated by concentrated nitric acid, is transformed into a brown powder, forming, when dissolved in alcohol, a red or violet liquid. Sometimes, also, it forms gold-like crystals, similar to

NEWS

murexide. Nitric acid colours all sorts of naphthylamine violet."

2. “When chlorine is passed into an aqueous solution of hydrochlorate of naphthylamine, it takes a violet colour and a brown resin is separated.”2

3. "The salts of naphthylamine, treated by perchlo ride of iron, chloride of gold, or nitrate of silver, produce a purple precipitate, soluble in alcohol and ether, to which they impart a violet colour."3-Comptes-Rendus.

PHARMACY, TOXICOLOGY, &c.

On the Conversion of Monohydrated into Common
Phosphoric Acid, by J. M. MAISCH.

SINCE the investigations of Graham into the nature of phosphoric acid, and his important discovery of the three hydrates, which form three corresponding series of salts, no further researches appear to have been instituted. The standard works on chemistry contain scarcely any thing beyond an abstract of the statements made by Graham about thirty years ago, and thus it happens that we know very little yet about the transition of one hydrate into another one. Starting with the phosphate of lime in bones and the common phosphate of soda, the pyrophosphate of soda and metaphosphoric acid have undoubtedly been often the subject of experiments. What is known, however, of the reconversion of meta and pyrophosphoric acid into the ordinary tribasic acid is contained in the following paragraph of Graham's "Elements of Chemistry":"When solutions of the metaphosphate and pyrophosphate of water are warmed they pass gradually into the state of common phosphate, combining with an additional quantity of water; and the metaphosphate of water appears then to become at once common phosphate without passing through the intermediate state of hydration of the pyrophosphate." Otto says that on boiling the solution of metaphosphoric acid it is very rapidly converted into the common acid, without, it seems, previously forming the deutohydrate. The glacial phosphoric acid consists chiefly of HO PO,. To obtain from it the ordinary acid would appear to require merely to warm or boil its aqueous solution. On making the experiment, however, it will not be found so easy as supposed. The committee having charge of the final revision of the Pharmacopoeia experienced this difficulty, and handed the subject over to me for investigation.

It is well known that the monobasic acid produces gelatinous precipitates in the solutions of most metallic oxides, coagulates albumen, and after neutralisation yields with nitrate of silver a white precipitate. The deutohydrate resembles the former only by precipitating silver salts white after it had been previously neutralised. The terhydrate under the same circumstance yields a yellow precipitate. For the following experiments Merck's glacial phosphoric acid was employed, and care taken to select pieces perfectly transparent and free from

earths and other acids.

If some of this glacial phosphoric acid is thrown into cold water it is slowly dissolved, and the solution shows the above reactions of the monohydrated acid. Set aside at our summer temperature for two or three weeks the solution ceases to coagulate albumen, and yields now a purely yellow coloured precipitate with alts of silver.

1 Liebig, Chimie Organic, vol. iii., p. 178.

2 Ibid., vol. iii, p. 179.

3 Piria, Annales de Chimie, vol. xxxi., p. 217.

The acid has been converted into the terhydrated, and apparently without becoming first the deutohydrate; for in proportion to the decrease of the coagulation the yellow colour of the precipitate becomes more apparent. The change is not brought about suddenly, but gradually; and similar is the behaviour of the deutohydrate. Dissolved in water, it is gradually converted into the terhydrate. It is very probable that the bulk of the solution and its density-that is, the concentration of the solution-may have a marked influence on the time requisite for forming the terhydrate, as I shall show in another place, but my experiments were not extended so far.

When a strong solution of metaphosphoric acid in water is heated to the boiling point, and the boiling continued with the pcaution to condense the evaporating water, or most of it, in the retort, so that the solution may at no time assume a syrupy consistence, it will be found that the bulk of the precipitate produced in a hour or two, according to the amount operated with, solution of albumen will gradually lessen, and after an will cease entirely; but now and at all times during the ebullition, the liquid, neutralised with soda or ammonia, produces a white precipitate with nitrate of silver, free from any tinge of yellow. The solution, it appears, contains pyrophosphoric acid, and is not perceptibly changed on continuing to boil for several hours more.

The syrupy liquid contained in bottles filled with glacial phosphoric acid, after having absorbed some moisture, consists at first of the mono- and deutohydrate, dissolved in water; heated to boiling, it changes very slowly into the bibasic acid. As the conversion proceeded much slower than in the former instance, experiments were made with a very dilute solution. the glacial acid in eight or ten fluid ounces of water, This diluted solution, containing about a drachm of about twenty minutes it had lost the property of coaguwas heated to boiling and kept at this temperature; in lating albumen; but previous to this, the precipitate with silver was perceptibly yellow, though not quite as deep coloured as from the common phosphate of soda. after the liquid ceased to coagulate albumen, and if the This precipitate had not become of a deeper yellow boiling was continued for several hours, little change could be perceived. It was evident that the solution contained some terhydrate and deutohydrate mixed. Experiments were now made with the same solutions, the strong, syrupy, and dilute, at temperatures between 1100 and 200° F. In all instances the result was similar to that just described, with the exception that generally a longer time was required to alter the monohydrate, the lower the temperature was to which the solution was exposed. Now, too, the strong solutions afforded no evidence of the presence of the terhydrate after the monohydrate had disappeared, while the weak solution, the colour of its silver precipitate. on the contrary, contained terhydrate, as was shown by

contains common phosphoric acid, which, after evaporaIf phosphorus is oxidised by nitric acid, the solution tion, may by heat be converted into the deuto- and monohydrate. If the monohydrate is now dissolved in diluted nitric acid and heated, it will lose its property of coagulating albumen, and will produce a yellow precipitate with silver salts, identical in colour with that obtained from the common phosphate of soda. This change in the presence of nitric acid does not appear to be unaffected by the density of the solution; but, as before, a more dilute solution is more readily converted into the tribasic acid than a concentrated one, and

62

The Behaviour of Essential Oils to Iodine and Bromine

apparently without the previous production of the

bibasic acid.

At first, I supposed that the metaphosphoric acid contained some compound requiring oxidation, before the change could be effected, but a careful trial showed the absence of any nitrous acid vapours by the time the conversion was complete. It is, likewise, not the presence of another mineral acid which effects the change of the mono- into the ter-hydrate; for when boiled with hydrochloric acid, the solutions scarcely yield more of the terhydrate than is obtained by the aqueous solution alone, while pyrophosphoric acid remains mixed with it, and an addition of common phosphoric acid does not exert any influence on the solution provided it be perfectly free from nitric acid.

That the cause cannot be looked for in the higher temperature necessarily produced by the addition of nitric acid is evidenced by the facts that the more concentrated solutions of the glacial phosphoric acid yields no terhydrate by boiling, while the diluted solutions boiling at a lower temperature, yield some, and that after the addition of nitric acid, the liquid need be but heated to near its boiling point to effect the change completely though more slowly than by boiling. The density of the solution, as will be seen from the above statements, exerts a strong influence in this process; but nitric acid converts both concentrated and diluted solutions into the common phosphoric acid.

It will require more and very careful experiments to determine precisely the way in which nitric acid acts in this case. That nitric acid merely acts as a catalytic agent, seems probable, from the absence of nitrous acid vapours; but it might be possible that a compound between metaphosphoric and nitric acid is formed for a short time, and decomposed again into nitric acid and the common phosphoric acid; or the monohydrated acid might be oxidised to a still unknown oxide, PO, or PO,, which is instantly decomposed into common phosphoric acid and oxygen, the latter in its nascent state uniting with NO, or NO, to form nitric acid again. Certain it is, that a small quantity of nitric acid will, with proper precaution to prevent its evaporation, change a considerable amount of metaphosphoric acid; and it acts quite or nearly as quickly upon the pyrophosphoric acid.

CHEMICAL NEWS,
Feb. 1, 1862.

On the Behaviour of Essential Oils to Iodine and
Bromine, by JOHN M. MAISCH.

THE reaction of iodine with the essential oils has first
been noticed and recommended as a test by Dr. Tuchen,
a German apothecary; it has subsequently been studied
by Winckler, Beschoener, Flashaff, Walker, and others,
and particularly by G. H. Zeller, who has laid down his
classical researches on the properties of the essential oils
in his important work, "Studien über die ætherischen
Oele." He has also first directed attention to the im-
portance of employing certain quantities and proportions
of the oil and of iodine, so as to make the examinations
under conditions as nearly alike as possible. His sug-
gestions were to place five or six drops, according to
their size, of the oil in a watch crystal and add to it two
grains of iodine, previously fused and rubbed into
powder; the iodine is to be added at one time and right
into the middle of the oil; after the reaction has ceased,
the oil is stirred with a glass rod, and the nature of the
mixture is noted. If oils of a thicker consistency are
tested, Zeller has been in the habit to heat slightly the
crystal containing the oil. In all the following experi-
ments, I have omitted this precaution of Zeller, because,
undoubtedly, the reaction between the oil and iodine is
increased by the application of heat, while it appears to
me essential for the detection of adulterations by cheaper
oils, to be familiar with their behaviour under like
circumstances and conditions.

Acting under this conviction, I have taken the precaution to make the experiments at a medium temperature, selecting the medium heat of summer, ranging from 70° to 85° F.; but few experiments were performed at a higher temperature, and they were verified or corrected at the lower one mentioned. By adopting these limits, I thought to confine the influence of heat within practical bounds, which may easily be observed in all cases without any great inconvenience.

behaviour of a few of the oils to pure bromine will be noticed under their respective heads; it was employed by allowing a drop of bromine to fall in the centre of five or six drops of the volatile oil, placed in a watch crystal. By the violent reaction which was shown by all, I was induced to think of a diluent for the re-agent, and found ether to answer this purpose best.

The difference in the reaction of iodine with volatile oils suggested to me the idea of employing bromine, which, while in its chemical properties closely resembling iodine, has for this purpose the advantage of being in a liquid state, so that a more energetic and complete action was to be expected from it. This expectation was verified Graham, though he does not state so, undoubtedly by experiment, but I soon found that it was so violent operated with diluted solutions of metaphosphoric acid, as to most likely exclude the possibility of noticing a by which his statement above quoted will be partly ex-difference occasioned by the presence of other oils. The plained, and the entire conversion into the terhydrate is merely an oversight, as a partial change only takes place. It is self-evident, that if a portion is thus altered, there ought to be a possibility of altering the whole in a like manner; the difficulty appears to consist in placing the entire solution in the same favourable condition, which is the proper large amount of water, and probably a certain temperature, which, when at the boiling point, induces the change most rapidly. If the proper conditions are ascertained, we may perhaps succeed in converting the entire bulk of a solution into the terhydrated acid; but an important point must be to prevent the formation of the deutohydrate, which, it appears to me, offers under all circumstances more resistance to form the terhydrate, than the pure monohydrate. Both, however, when in solution, succumb to the influence of time and of nitric acid, assisted by heat. Of the behaviour of the three hydrates in their free and combined state to reagents, we still know too little, though it is an important and at the same time an interesting subject for further researches.-American Journal of Pharmacy.

An

After some trial experiments, I have selected a solution of one measure of bromine in about five measures of officinal ether; with a solution of this strength the reaction does not proceed too quick, while the changes in colour and consistency may be easily observed. ethereal solution of bromine is decomposed spontaneously; it is, therefore, best to prepare it extemporaneously. While mixing the two liquids some caution is necessary to prevent their becoming heated, as decomposition would take place, and so much of both liquids volatilised that the resulting mixture would be of uncertain strength It is, therefore, best to immerse the vial containing the ether in cool water, and for each fluid drachm of this solvent add fifteen drops of bromine to it. To five or six drops of an essential oil placed in a

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