Obrazy na stronie

Oct. 13, 1865.


Notes on the Fracture of Polished Glass Surfaces. smoke-colour glass. The results exhibited were after an many advantages-especially as regards the tenacity, exposure of eight days, and showed that the parts of the hardness, and homogeneous character of the metal proboard directly exposed to light were bleached ; those duced. This he proposed to apply to the manufacture protected by an opaque medium were not acted upon; of tubes, sheathing, cylinders for calico printers, and while with the glasses of different colours intermediate manifold other purposes. effects were produced, those of the violet glass being most Since the date above mentioned, Mr. Parkes has obdecided. Drying oils in conjunction with light rapidly tained other patents for modifications and improvements bleach sulphide of lead, and boiled oil effects the bleach- in his original process, and the manufacture of phosphoring still more rapidly. When water colour is used ised copper, containing from š to, į per cent. of bleaching takes place, but much more slowly than in the phosphorus, is now successfully carried on at the extencase of oil. After quoting authorities, stating that gene- sive works of the Stephenson Tube Company, in Birmingrally light was advantageous to the preservation of ham, with which the patentee is connected. pictures, Dr. Price showed a striking illustration of this This metal is forged, drawn, and rolled both hot and fact. He had a picture painted, and then exposed it to cold, and its successful application to the manufacture of the action of sulphuretted hydrogen, until it became tubes, cylinders, sheets, and various other purposes, has sadly discoloured, and to all appearance destroyed. established its claim to the possession of those qualities Some strips of paper were laid across the picture, so as which are stated by Mr. Parkes to be its especial chato cover some parts. The picture, thus partially covered, racteristics — viz., great hardness, homogeneousness, was exposed to light for a long time. The result, as smoothness and evenness of texture, and tenacity. Its shown at the meeting, was very curious indeed, the parts employment for the manufacture of large cylinders for of the picture exposed being perfectly restored, while calico printing has been especially satisfactory, by reason those protected by the paper remained still discoloured. of these qualities. From his experiments he came to the conclusion that it The successful issue of the whole manufacture appears, was advantageous to have picture galleries well lighted, however, to depend upon the careful selection of mateespecially where, as in towns, the atmosphere was rials, and upon certain niceties of manipulation, which charged with sulphur compounds, and that it was quite are absolutely indispensable. a mistake to have curtains placed in front of pictures, with a view to their protection. In the course of his

PHYSICAL SCIENCE. communication Dr. Price referred to the use of zinc paint for houses, and considered it likely to be acted upon, as

Notes on the Fracture of Polished Glass Surfaces, the paint was rendered soluble by the acids contained in

by F. H. WENHAM.T the atmosphere of towns.

The short communication which I submit to your notice

scarcely merits consideration as a discovery; but as the Compounds of Copper and Phosphorus, by microscope has in this case immediately detected the Mr. F. A. ABEL.*

cause of a well-known phenomenon, I bring it forward

as an example of the use of the instrument in practical This paper was devoted to the description of a series of investigations. experiments made to ascertain if phosphorised copper It is a fact known to the philosophical instrument would be more effectual as a material for the manufac-makers that if a metal wire be drawn through a glass ture of cannon than the alloy now in general use. After tube, a few hours afterwards the tube will burst into referring to the different chemical compounds of copper fragments. The annealed glass tubes used for the waterand phosphorus known, Mr. Abel spoke of his experi- gauges of steam-boilers are sometimes destroyed in this ments on phosphorised copper, with respect to its tensile

way, after the act of forcing a piece of cotton waste strength. He found that an ingot of copper one inch in through them with a wire for the purpose of cleaning area broke under a strain of about 25,000 lbs., that of a the bore. This will not happen if a piece of soft wood similar ingot of gun metal required 32,000 lbs. Whilst

is employed. copper combined with 5 per cent. of phosphorus required The late Andrew Ross informed me that on one occa38,389 lbs., and with 14 per cent. of phosphorus the sion, late in the evening, he lightly pushed a piece of strain that the ingot would bear was upwards of 47,000 lbs. cotton wool through a number of barometer-tubes with Although these experiments showed the very superior a piece of cane, for the purpose of clearing out any partenacity of the phosphorised copper, yet there were ticles of dust. The next morning he found most of the practical difficulties which prevented the application of tubes broken up into small fragments, the hard siliceous This compound to gunnery. In the course of the discus-coating of the cane proving as destructive as he had sion which followed the reading of this paper, Mr. Abel previously known a wire to be. stated that this phosphorised copper would not be at all

After having drawn the point of a steel burnisher suitable for telegraphic purposes, as the presence of over the surface of a slip of polished glass, the following phosphorụs was most detrimental to the metal as a con- appearances will be observed under the microscope, using ductor of electricity,

the polarising apparatus and selenite plate, with a twoAfter the paper of which the above is an abstract had thirds object-glass. A coloured stripe is visible in the been read, Mr. A. W. Wills made the following state- passage of the burnisher, showing that the surface of ment:-

the glass has been placed in a state of tension in the So long ago as 1848 a patent was taken out by Mr. direction of the line. The glass, too, seems not altoAlexander Parkes, of Birmingham, for the use of com-gether devoid of plasticity, for the waves of colour pounds of copper, zinc, nickel, and other metals, with show that it has been carried forward in ripples, rephosphorus. The result of Mr. Parkes' experiments, more sembling the mark left on a leather-bound book after the especially with respect to the copper compounds, had passage of a blunt point. It may be inferred from this been so favourable as to enable him to claim for them that the mere burnishing of the surface of the glass * Read at the meeting of the British Association.

† Read before the Microscopical Society.

[ocr errors][merged small][merged small][merged small]

with a substance inferior in hardness will, without any that complaints are made that the existing fiscal scratching, cause an irregular strain in the bore of restrictions imposed on the production and assessment tubes sufficient to split them, and the concussion of dutiable commodities are unnecessarily stringent, attendant upon the fracture often reduces the tube to and that a relaxation of such restrictions might safely small fragments.

be allowed. Some of these complaints are, no doubt, If the burnished lines apon the glass slip be examined well founded and deserving of serious attention, but a few days afterwards, the colours will have become others are insidious, and the pleas upon which they much less visible, showing that the strained portions of are based require to be examined with the utmost care, the glass partly recovers its equilibrium.

under the guidance of the laws and regulations reOn attempting to polish out a minute scratch on the lating to the collection of the revenue, and also by surface of a piece of glass, it sometimes appears to scientific investigations of the modified processes which widen during the process, and at length resolves itself may be proposed as beneficial to trade, but which, if into two irregular parallel rows. Also, a clean cut sanctioned, might lead to frauds on the revenue. Thus, made with a diamond on a piece of plate-glass, if left the number of samples analysed does not give a full for a time, the surface in the vicinity of the cut will idea of the extent of the business of the laboratory, break up, forming a coarse irregular line. If the dia- as the researches and investigations undertaken for mond be raised and struck lightly on the surface of the special objects, and which demand much time and glass, the form of the edges of the short stroke thus made thought, are not included. As an instance, it may be may be plainly seen, using the binocular polariscope. proper to mention the following case, which is now A conical ridge of glass appears to be left with its apex depending :- The hop planters of Kent, being desirous under the line of ihe cut, and the glass is frequently to avail themselves of duty-free tobacco for the purpose wedged up on both sides of the ridge, explaining the of destroying the insects which infest the hop plant, cause of the double line of fracture which sometimes memorialised Government on the subject, and the quesmakes its appearance in polishing out a scratch. This tion being submitted to me, a series of experiments effect may also be exemplified by observing the marks were at once commenced to discover some mode by left on a polished glass surface from the light blows of a which the extract of tobacco intended to be used might steel centre-punch. The point of the punch drives in be rendered unfit for the purposes of fraudulent tobacco an atom of the glass, and the fracture extends some manufacturers, without causing it to be injurious to the distance into the interior, expanding downwards in the hop plant. The problem may appear simple, but it was form of a truncated cone. The polariscope shows that soon found to be very difficult of solution, and all the the conical centre is in a state of compression, and that substances hitherto tried, which, when added to the the surrounding exterior portion of the glass is also tobacco extract, could not again be separated effectually, under strain.

and which would prevent an improper use of such exThe smooth, round edge of a glazier's diamond, when tract, have proved to be injurious to vegetation. Expedrawn over a polished glass surface, burnishes down riments are still going on, and I hope to be able soon to and compresses the glass beneath the cut, and in the surmount the difficulty. case of thin sheets the wedge-like force of the com- During the last financial year the Act allowing duty. pressed line splits the glass nearly through ; but when free male to be used in the feeding of animals came into the glass is thick and rigid, as plate-glass, unless the operation, and up to March 31 last 519 samples of mixsheet is bent back and broken through immediately after tures of malt and linseed prepared for the purpose menthe cut, greater difficulty will be experienced if allowed tioned, and 365 samples of ground linseed alone, had to remain for a time, for the compressed line of glass been examined in the laboratory; and it is satisfactory will speedily tear up the portion on both sides, leaving a to be able to state that, with two or three exceptions, wide ragged groove in place of the original clean and the whole of the samples were found to be totally unfit scarcely visible line.

for the brewing of beer, thus proving that the revenue

derived from malt is not, as it was by some feared it THE EXCISE LABORATORY.

would be, endangered under the provisions of the Act in

question. REPORT FROM THE PRINCIPAL TO THE COMMISSIONERS The stringent measures adopted by the Customs to OF THE INLAND REVENUE, 1865.

prevent the importation of simulated wines are still conIn my last Report I alluded to the fact that, owing tinued, and 182 samples have within the year been to recent legislation, the business of the laboratory had examined, of which 102 were found to be composed altered considerably in character, and that, although chiefly of factitious wine, whilst nearly the whole of the the aggregate number of samples examined during the remaining. 70 were of very low value, and, although year was much less than the number examined in the genuine wine predominated more or less in their compoprevious year, the amount of work performed was sition, they still contained considerable proportions of much greater. In reverting to this subject, at the risk spurious wine.

There can be no doubt but that these of being charged with giving undue prominence to it, made-up liquids would, but for the energetical action of I am actuated solely by a desire to show that the ope- the Customs, have passed into consumption either per se rations of my department, as subsidiary to a highly as sherry, or mixed with genuine wine. organised system of levying and securing a large re- Within the past year two manufactories have been venue, have not lessened, but are steadily increasing established in London for the purpose of preparing gluin importance. That this should be the case is not cose or starch sugar for the use of brewers, and as this surprising, as the invention and adroitness brought to sugar differs considerably both in value and character bear on the acquisition of wealth are daily becoming from cane sugar, to which alone the existing rates of duty more refined, and more adopted by enterprising per apply, it has become necessary, for the purposes of assess

Occasionally bold attempts are made to circum- ment, to determine the ratio of dutiable value of the two vent the revenue under the guise of new and legiti- descriptions of sugar, and for this end 12 samples of glumate objects of trade, whilst it not infrequently happens coge have been analysed.



The Excise Laboratory.

Oct. 13, 1865.

in the

of Ireland.


[ocr errors]




Number of Samples

examined excluding
Coffee and Chicory,
and also those from




From the examined.



22 21

6251 6309


Analyses for the Customs continue to form a consider- from the article, and the following table may not be able proportion of the work devolving on the laboratory, uninteresting, as showing that the consumption of duty as during the past year no less than 2259 samples were paid tobacco has more than kept pace with the increase examined for that branch of the revenue.

of population in the United Kingdom :The progress of the business of the laboratory for the

Total population

Pounds Weight of Weight of last four years will be seen from the following table, in

of Great Britain,

Tobacco cleared Tobacco yearly Year.

for consumption consumed per which the samples of coffee and mixtures of chicory and

and approximately

bead of the coffee are distinguished from the other samples

United Kingdom. population. 1841 26,700,000 23,096,281

131 Number of Samples


27, 347,000 27,734,786 examined.

1861 28,887,000


35 Total

Number of

29,195,00 37,636,240
Coffee and

Population estimated according to the percentage in.

crease during the decennial period from 1851 to 1861. of Chicory and Coffee.

A few cases of the adulteration of tobacco with liquorice have been detected during the past year, but

the quantity of liquorice used was very small. In two 8364 3045


instances which occurred in London the tobacco con1862 5088 11360

71 tained not more than 1 per cent. of the illicit ingredient. 1863 25 2254 8588

2772 The practice of illegally using liquorice and other sac1864 8388 61 2259 10708

charine matter still lingers in Ireland, but the numerous

detections which were some time ago made, and the Thus, during the period to which the above table refers ro less than 42,000 samples have been analysed, an

penalties imposed, appear to have had a salutary effect, amount of work the results of which cannot have failed as the fraud, when now committed, seems to be done to exercise a beneficial effect not only upon the interests timidly, and not in that gross and daring manner of the revenue, but upon those of the community in the impression that the Revenue possessed no satis

which was the case when the offenders were under general. In the educational branch of the laboratory ten young of the fraud.

factory means of proving, by analysis, the commission officers have, since the date of my last Report, completed

As in previous years, I have myself closely inspected a course of study in chemistry, and in their final examination by Dr. Hofmann they acquitted themselves in such a large number of the tobacco manufactories in the a manner as to draw from that gentleman a very high kingdom, and I am in a position to say, from my own encomium. This satisfactory result is mainly due to observation, that the adulteration of tobacco is now the intelligence and assiduity of the students them

almost nominal. selves, who, in common with their predecessors, have been deemed necessary to examine 158 samples under a

It will be seen from the following table that it has shown a desire to profit to the utmost by the oppor- suspicion that they were illicit, but of these only 34 were mination to merit the approbation of the Board. Fifty: to defraud the Revenue as to impart à particular character and have evinced an earnest and praiseworthy deter: adulterated, the most of them to so slight an extent as

to lead to the inference that the object was not so much nine students have now passed through a course of

to the tobacco :-
education in chemistry, and it is perhaps not too much
to say that they form a valuable reserve from which Year.

Number of Samples.

Total. officers may be selected to assist in securing the revenue 1862.


109 in those cases in which it may be advantageous to 1863. 69

100 make their scientific knowledge available. At the pre- 1864. 124

158 sent time only six students are under instruction, as Of the adulterated samples, three contained caneowing to the limited space at the disposal of the de- sugar, four cane-sugar and liquorice, fourteen liquorice, partment, and the increase of the practical business of four coltsfoot, one cabbage leaves, two sulphate of iron, the laboratory, it was found difficult to spare room for one lamp-black; whilst five samples of “ fancy tobaccos” more.

contained stramonium, coltsfoot, lavender, and southern. During the period to which this Report relates four wood. teen examiners have received in the laboratory a month's

(To be continued.) instruction in the modes of detecting the adulteration of articles subject to revenue duties ; 170 of these officers, Manufactare of Arsenic Acid.-Girardin suspends whose position in the service is highly onerous and powdered arsenious acid in water, and passes chlorine demands much intelligence and practical knowledge, have into the mixture, by which he soon obtains a clear passed, on the whole, with great credit through my solution of arsenic acid in hydrochloric acid. By evapodepartment.

rating this solution a mass of arsenic acid containing no Tobacco.— The condition of the trade in this im- trace of arsenious is procured. As it is difficult to keep portant commodity, so far at least as relates to the any considerable amount of arsenious acid in suspension question of adulteration, continues in a most healthy solution' of that acid in hydrochloric, and pass the

in water, the author finds it better to make a saturated state; it cannot, of course, be supposed that an article chlorine into such solution while hot. The stream of upon which is imposed a duty of about 500 per cent. on chlorine is stopped when a little of the fluid neutralised its value, should escape the attention of the smuggler or with potash no longer gives a green precipitate with the adulterator, and it can only have been by well-directed bichromate of potash, thus showing that all the arsenious and sustained efforts that frauds on the tobacco rovenue acid has been converted. The hydrochloric acid may then have been kept down to a minimum which is insignifi. be recovered by distillation, and the syrupy solution of cant when compared with the large yearly duty derived ) arsenic acid left in the retort evaporated.


31 34

[ocr errors][merged small][merged small][merged small]


we distinguish by the simplest experiments. On opening the sealed tubes of the vessels under mercury, no change

takes place in the case of hydrochloric acid, ammonia, and ROYAL INSTITUTION OF GREAT BRITAIN. marsh-gas, while the mercury immediately rises and fills Weekly Evening Meeting, Friday, April 7.

the globe containing the condensed water vapour. When H.R.H. The Prince of Wales, Vice-Patron, in the Chair. the broken points of the tubes to dip in a layer of water

the remaining three vessels are now raised, so as to allow On the Combining Power of Atoms.

floatir on the mercury, the liquid rushes into the globes By Dr. A. W. HOFMANN, F.R.S.

containing hydrochloric acid and ammonia ; of the two (Continued from page 169.)

solutions thus produced by the absorption of the gases, In the preceding remarks, I have submitted to you an the one containing the hydrochloric acid reddens blue extensive series of examples taken from different pages in litmus ; the other, formed by the absorption of the ammothe vast volume of chemistry, which appear to indicate nia, changes red litmus to blue. The marsh-gas differs that oxygen combines atom by atom, that nitrogen enters from all the others by its insolubility and by its inflammathe compound freighted with one atom of hydrogen, and, bility. Indeed, if the globe be broken and á light applied, capital, so to speak, of two atoms of hydrogen. supposing, or are the differences observed in the structure of these for a moment, that this rule could be established without four hydrogen compounds less characteristic, although a single exception throughout the whole range of chemis- they cannot be so easily demonstrated by experiment,-at try, are we enabled to assign a probable reason for this all events, within the limited time at my disposal. Indeed, peculiar behaviour of the oxygen, nitrogen, and carbon to give you an idea of their structure which is necessary atoms?

for our purposes, I must be permitted to borrow a leaf To answer this question we must commence by con- from the book of the Wizard of the North, and to avail sidering for a few moments some of the simplest compounds myself of a simple mechanical contrivance devised for that of the elements concerned.

purpose. Let these four tin boxes represent two volumes Here we have four glass tubes surmounted by large of hydrochloric acid, water-gas, ammonia, and marsh-gas. globes. The first of these contains hydrochloric acid, the We wish to know the quantities of hydrogen contained compound of hydrogen with chlorine; the second did in two volumes of each of these four bodies, and we find contain the vapour of water,—the compound of hydrogen that out of the two volumes of hydrochloric acid we are with oxygen—but which is now condensed to small drops enabled to pull one volume of hydrogen ; out of the same of fluid water deposited on the sides of the globe; in the volume of water-vapour, two volumes of hydrogen; out of third ressel we have the compound of hydrogen with the same volume of ammonia, by a mechanical contrivance nitrogen, ammonia ; while the last is filled with one of the of the simplest description, three volumes of hydrogen ; compounds of carbon with hydrogen, viz., marsh-gas. and, lastly, out of two volumes of marsh-gas, four volumes

These four compounds, all transparent and colourless, of hydrogen.

[ocr errors][merged small][merged small][merged small][merged small]

We now require to know the quantities of the other | ammonia, one of nitrogen ; and, lastly, from the two elements present in the four compounds under examina- volumes of marsh-gas, an amount of carbon which protion, and again we extract from the original two volumes i visionally I may be permitted to represent by one volume, of hydrochloric acid one volume of chlorine ; from the two since, owing to the non-volatility of the carbon, the volume volumes of water-vapour, one of oxygen; from the two of of the carbon-vapour has not yet been ascertained.

[graphic][ocr errors][merged small][ocr errors][merged small][ocr errors][ocr errors][graphic][merged small][merged small]


Royal Institution of Great Britain.


Oct. 13, 1865.

FIG. 4:



| Na

[ocr errors]

The information mechanically conveyed to us by our different gases be submitted to the same pressure they tin boxes is embodied in the following diagram, which is, contract to an equal extent, and if they are equally heated moreover, calculated to enlarge our views respecting the they expand equally. combining powers of the elements chlorine, oxygen, We have an apparatus (Fig. 5) so disposed as to permit us nitrogen, and carbon :

to establish this point experimentally. It consists of a kind of double U tube, with one long and simple limb,

and one short limb bifurcated into two branches, each of Hydrochloric Acid. Chlorine (Molecule). Chloride of

which is provided with a stopcock. These short limbs lium.

are, moreover, surrounded by a glass cylinder. Near the

bottom of the apparatus another stopcock is placed, H Ci

| Na : Ci enabling us to empty the apparatus. The three limbs of

the instrument being filled with mercury, we introduce
into the stopcocked limbs the gases to be examined, into

the one hydrogen, and into the other oxygen, care being Hypochlorous Anhydride. Oxide of Sodium.

taken to have as nearly as possible equal volumes of the two. These volumes being marked by caoutchouc rings,

we pour mercury into the long open limb, and we find H CI


that the mercury column thus obtained compresses the

two gases to an exactly equal extent. Again, on letting 0


out mercury through the bottom sropcock, so as to lower

the column and diminish the pressure, we observe that H


| Nai

both hydrogen and oxygen undergo equal dilatation. And so, again, we are enabled to prove the expansion and contraction of the two gases to be equal, if the glass cylinder

surrounding the bifurcated limb of the apparatus be filled Ammonia. Chloride of Nitrogen.

Trisodamide. alternately by hot steam or cold air.

Now, if equal volumes of the elementary gases contain

an equal number of atoms, it is obvious that
The chlorine atom combines with ; atom of hydrogen,

2 atoms
» nitrogen

3 H N Ci N

Na N

and since there are reasons for believing that the quantity of carbon existing in two volumes of marsh-gas (but

which, as I have pointed out, has never been obtained in H CI


the gaseous state) represents the carbon atom, we may add that

The carbon atom combines with 4 atoms of hydrogen.

And in a similar manner we may say that the atoms of Marsh Gas. Tetrachloride of Carbon. Sodium-methyl.

the four elements in question, when uniting with chlorine, are found to be capable of fixing 1, 2, 3, or 4 atoms of

chlorine. H

| Na

These observations, which, if time permitted, might be considerably expanded, lead us to a very important dis

tinction of elementary atoms, which is based upon their H

atom-fixing capabilities, more shortly expressed, upon H

their combining powers.


If the atom-fixing power of the chlorine atom be taken

as standard of comparison, we are compelled to assign to H CI


the oxygen atom the twofold, to the nitrogen atom the threefold, and to the carbon atom the fourfold atom-fixing power; or, looking at this question from a different point

of view, we find that one atom of oxygen is performing II CI


the work of two atoms of chlorine; one atom of nitrogen, that of three ; one atom of carbon, lastly, that of four

atoms of chlorine. Hence we distinguish the chlorine In the second column of the diagram are given the atom as univalent, the atom of oxygen as bivalent, that compounds of these four elements with chlorine, and of nitrogen as trivalent, and, lastly, the carbon atom as exactly as we have seen them combining respectively with quadrivalent. I, 2,

31 and


volumes of hydrogen, we now find them With the recognition of these different combining associated with 1, 2, 3, and 4 volumes of chlorine. Again, powers in elementary atoms we have made a very con. in the third column we have the series of sodium com- siderable step towards the solution of the question which pounds of these elements, and although in this case we presented itself in the earlier part of this discourse-riz., must be careful not to speak of volumes of sodium-vapour, How is it that the oxygen atom is fixed directly, the since chemists have not as yet obtained sodium-gas in the nitrogen atom together with one, the carbon atom, lastly, pure state, we perceive at all events from the diagram that together, with two atoms of hydrogen ? This peculiar one volume of oxygen fixes exactly twice, one volume of mode of combination is the necessary consequence of the nitrogen exactly three times the quantity of sodium which special atom--fixing capabilities of the oxygen, nitrogen, is combined with one volume of chlorine.

and carbon atoms ; and this I believe I can show you by The study of elementary gases has led chemists to the a very simple contrivance. I ain again tempted to rely unanimous opinion that equal volumes of these different entirely on mechanical me of elucidating the subject, gases contain an equal number of the smallest particles or and I will on this occasion, with your permission, select atoms. Numerous theore:ical considerations and numerous my illustration from that most delightful of games, croquet. experimental inquiries inevitably lead to this result, which Let the croquet balls represent our atoms, and let us is now a generally received truth. If equal volumes of distinguish the atoms of different elements by different

[ocr errors]
[ocr errors]
[ocr errors]
[ocr errors]
« PoprzedniaDalej »