NEWS

THE CHEMICAL

VOL. XXXIV. No. 883.

ON REPULSION RESULTING FROM

RADIATION.-PART II.*

By WILLIAM CROOKES, F.R.S., &c.
(Continued from p. 166).

87. With a large bulb, very well exhausted and containing a suspended bar of pith, a somewhat striking effect is produced when a lighted candle or other radiant source is brought about 2 inches from the globe. The pith bar commences to oscillate to and fro, the swing gradually increasing in amplitude until the dead centre is passed over, and then several complete revolutions are made. The torsion of the suspending fibre now offers resistance to the revolutions, and the index commences to turn in the opposite direction. This movement is kept up with great energy and regularity as long as the candle burnsproducing, in fact, perpetual motion, provided only the radiation falling on the pith be perpetual. If the candle is brought closer to the bulb, the rotation of the pith becomes more rapid; if it is moved further away the pith ceases to pass the dead centre, and at a still further distance the index sets equatorially. The explanation of the different movements of the pith index according to the distance the radiant body is off, is not difficult on the supposition that the movement is due to the direct impact of waves on the suspended body.

88. It is not at first sight obvious how ice, or a cold substance, can produce the opposite effect to heat, cold being simply negative heat (33). The law of exchanges, however, explains this perfectly. The pith index and the whole of the surrounding bodies are incessantly exchanging heat-rays; and under ordinary circumstances the income and expenditure of heat are in equilibrium. A piece of ice brought near one end of the index cuts off the influx of heat to it from that side, and therefore allows an excess Attraction of heat to fall upon it from the opposite side. by a cold body is therefore seen to be only repulsion by the radiation from the opposite side of the room.

Bearing the law of exchanges in mind, several apparent anomalies in the movements of these indices are cleared up; and it is also easy to foresee what the movement of a body will be when free to move in space under the inAuence of varying amounts of radiation.

The heat which all bodies radiate into space can have no influence in moving them, except there be something in the nature of a recoil in the act of emitting radiation. And even should there be such a recoil, if the body radiates heat equally all round, the recoil will be uniform, and will not move the body in one direction more than in another. I need therefore only consider the effect of the radiation received by a body. Here also the influx of radiation to a body free to move in space of a uniform temperature may be considered to be equal, and it will acquire the temperature of space without moving in any direction.

89. The case is, however, different if two bodies, each free to move, are near each other in space, and if they differ in temperature either from each other or from the limiting walls of the space. I will give here four typical cases, with experiments sufficient to prove the reasoning

to be correct.

Z,,,>

CASE II. Two cold bodies, A and B, in space of a higher temperature than themselves. A will receive much heat from space, except where B cuts it off, and on that side it will only receive slight radiation from B. A will therefore be driven towards B. In the same manner it can be shown that B will be driven towards A; and the result will therefore be an apparent mutual attraction.

CASE III. Two bodies, A hot and B cold, in cold space. The body A receives heat uniformly from all sides, even from that opposite B (B being of the same temperature as B receives heat unispace). A will therefore not move. formly from all sides, except from that opposite A, on which side the influx of heat is more intense. The result will therefore be that A remains stationary whilst B is repelled.

CASE IV. Two bodies, A hot and B cold, in hot space. The body A receives heat uniformly from all sides, except from that opposite B. Here the heat is less intense. A is therefore driven towards B by the extra influx of heat on the other side of A. B receives strong influx of heat from all sides, and just as much from the side opposite A as from any other. B will therefore not move. The result will be that A will be apparently attracted towards B, whilst B will remain stationary.

The force with which the bodies A and B in these four

176

WITH the view to study the actions of different fatty oils upon copper I made two series of experiments. In the first, which was commenced on the 1st October, 1875, I took twenty-six different samples and measured 150 grs. of each into bottles; into each bottle was then placed a piece of copper foil, 1 inch long by inch broad, so as to lie flat at the bottom of the oil. After a few days it was observed that some of the samples had acted on the pieces of copper, some had thrown on to the metallic surface a slight greenish incrustation, some had produced a dark coloured incrustation, and the remainder produced no effect on the bright metallic surface of the copper.

No special examination of either the metallic copper or the oils was made till they had remained in contact for ten months at the ordinary temperatures of the atmosphere.

* Read before the British Association, Glasgow Meeting (Section B.).

CHEMICAL News, Oct. 27, 1876.

The second series was commenced about one month later than the first, and differs from the first somewhat in the detail of its arrangement. Eighteen different samples were employed, each oil representing in both series a distinct and different sample, although in some cases two or more of the same kind of oil were employed, and I am indebted to the kindness of Mr. Wollaston, of Manchester, for the greater number of the samples used in both series and for the care which he exercised in obtaining samples which could be relied upon as being free from adulteration.

In this second series 300 grs. of each sample were placed in bottles, and a slip of well-cleaned metallic copper, 3 inches long by inch broad, put into each so that only one half of the slips was immersed in the oil, whilst the other half was exposed to the air.

The following is a list of the different samples used :— IN SECOND Series. Vegetable Oils.

IN FIRST Series.
Vegetable Oils.

1. Mesina olive oil.

2. Olive oil.

3. Rape oil.

4. Refined rape oil. 5. Cotton seed oil.

6. Pale cotton seed oil.

7. Cotton seed oil.

8. Linseed oil.

9. Almond oil.

10. Palm oil.

1. Olive oil.

2.

3. Pale rape oil.
4. Brown rape oil.
5. Cotton seed oil.
6. Raw linseed oil.
7. Palm nut oil.
8. Ground nut oil.
9. Castor oil.

Animal Oils. 10. Pure lard oil.

11. Common tallow oil. 12. American tallow oil. 13. English neatsfoot oil. 14. North American neatsfoot oil.

Fish Oils.

15: American sperm oil. 16. Whale oil.

17. Pure seal oil.

Mineral Oil.

18. Lubricating mineral oil.

All these samples of oil, together with the slips of metallic copper left in contact with them, were examined on the 9th of August, 1876, in the following manner :First. Each slip of copper was carefully examined and its appearance noted.

Second. The appearance of each oil was observed and noted.

Third. Ten grains of each sample were measured off by a pipette and placed in a small test-glass, and 5 grs. of a moderately strong solution of ferrocyanide of potassium added, and the oil and solution thoroughly mixed by stirring them together for some time and then leaving them for about a day. This method I found to give the of copper which had been dissolved by the oils; the characmost satisfactory result for testing the relative proportions teristic brownish red precipitate of ferrocyanide of copper being thrown down admitted of very accurate comparison.

Fourth. Fifteen grains of each oil were taken by means of a pipette, and each placed in a small stoppered test-tube; 15 grs. of distilled water were then added and each tube shaken violently. The tubes were then suspended in water and heated to about 200° F. and shaken violently two more times at intervals of one hour each, and allowed to remain in contact with the hot water at 200° F. for six hours; the source of heat was then removed and the oils allowed to remain over the night to allow the water to separate from the oils more completely.

NEWS

In the morning the water was drawn off from the tubes by a pipette having a long fine point, and each transferred to a small test-glass. A drop of each solution was then taken out by a clean glass stirring rod and spread across pieces of blue litmus paper in a series of lines side by side with each other, the intensity of redness thus produced by the acids dissolved by the water compared, and the results noted.

Fifth.-Five grains of a moderately strong solution of ferrocyanide of potassium were then added to each water solution above mentioned, the mixture stirred, and left for four hours, when the amounts of the precipitates of ferrocyanide of copper were observed comparatively and the results noted. The results of these observations I have arranged in tabular form.

(To be continued.)

PYROLOGY, OR ANALYSIS AND SYNTHESIS
BY THE BLOWPIPE.
By MAJOR ROSS, late R.A.
(Continued from vol. xxxiii.. p. 3.)

(11.) THE fact may have been noticed, with regard to the Scientific Loan Exhibition at South Kensington, that three-fourths of the apparatus, &c., there displayed are foreign, and that a great part of the remaining fourth, | although the property of English" Manufacturers," has in reality been produced in Paris, Berlin, or some other French or German town, while Sir W. Thomson, Sir. J. Hawkshaw, and others less celebrated, who have lately arrived from America, are unanimous in the opinion that, unless we are careful, the Americans will shortly pass us in those manufactures of which we have hitherto been most proud. In short, look on the matter as we may, deny the fact as we will, it seems doubtful if nationally England occupies more than the third place in scientific Europe.

(12.) The reason of this appears that, like everything else, scientific knowledge is made a mere matter of barter in England. Only rich men can here afford to do anything original in the way of physical or chemical experimentation.

:

(13.) Here then, briefly, is what the blowpipe will do for a student who takes it up with due appreciation:(a) The necessary apparatus is, or ought to be, cheapest of the cheap, even the balance required for quantitative analysis being the smallest and cheapest kind made. (b) Accurate observations can be made so rapidly that even the public teacher in chemistry and physics can thus most beneficially employ his little leisure. (c) The field of observation is almost entirely unoccupied, so that the disciple, unencumbered by the terrific terminology of chemistry, may after a short time bring contributions to physical science really worthy of her acceptance; while geology and mineralogy will after a time acquire a new zest from such examinations. (d) If our manufacturers were only equal to the Germans or French, a traveller's apparatus might be made for a few shillings, in a leather case, which would roll up and go into the breast pocket of a coat, enabling the investigator to start at a moment's notice for the country or abroad. I shall try to induce Messrs. Griffin to make up such a case of blowpipe necessaries, and to sell it as cheaply as possible.

(14.) All sciences are so linked together that a correlation can be shown to exist even between two of the most apparently widely separated. Few, for instance, would suspect that the political economist could derive any benefit from the study of blowpipe analysis, and yet the case of the tumble-down barracks and public buildings all over Northern Indian, publicly stated, without denial, to have cost the Government £40,000,000, between the years 1861-75, is one in point; but the account of this must be reserved for the next paper.

ON ANTHRACEN TESTING. By DR. FREDERICK VERSMANN.

IN a paper "On Anthracen and Alizarin," read before the Society of Arts in March, 1874, I ventured to express my opinion that the quinon test was not trustworthy, because it did not represent true anthracen convertible into alizarin, and also because the stipulated correction, equal to 1 per cent, made the whole process illusory.

At that time I stood alone in my opinion, but it is now perfectly well known among manufacturers and buyers of anthracen that the quinon test does not always indicate the exact and true value of the merchandise; and even Messrs. Meister, Lucius, and Brüning, who first proposed the test, now acknowledge its inaccuracy by issuing in last week's CHEMICAL NEWS (vol. xxxiv., p. 167) a new and improved method.

This new test differs from the previous one merely by an increase of the oxidising agent-chromic acid and its solvent acetic acid and water-and by the treatment of the quinon with fuming sulphuric acid instead of with potassium permanganate, and subsequent volatilisation of the remaining quinon.

The publication of this "new and improved method" induces me to collect the results of prolonged investigations on the subject, which, although not yet brought to a final conclusion, may tend to throw some light on the nature of the products obtained, and I am the more inclined now to publish my experience, because more than six months ago I tried the sulphuric acid myself, but found it neither satisfactory nor practical. In fact it was exactly the failure with sulphuric acid which induced me to follow up the subject in a different direction, and, as I believe, with more satisfactory results.

After boiling a sample of anthracen with chromic acid solution, and allowing the mixture to stand for hours, long, well-defined crystals separate, and on adding water a further separation takes place, not in the form of crystals, but of an amorphous powder. The product collected on the filter is always a mixture of crystals and powder, part of the last of which is again removed by potassium permanganate and potassium hydrate.

This observation induced me to collect the crystals and powder separately, and to ascertain their nature by practical tests applicable for commercial analyses. As such I adopted, above all, the melting- and solidifying-points, and then the action of potassium permanganate and potassium hydrate.

The determination of the melting- and solidifyingpoint I look upon as most important and valuable, and I can only express my surprise that it has not been introduced long ago, especially as it formed so important a part in the alcohol and bisulphide test.

I have collected in the following table some results from a great many, which fairly represent commercial anthracen from the lowest to the highest percentage. The first column gives the percentage of quinon actually obtained, i.e., without correction; the second and third columns give the crystals and powder separately; and the last column the number of drops of 5 per cent potassium permanganate solution required to leave a distinct colouration after prolonged boiling of each of the three products.

As to the operation itself, the first result was obtained by the usual test with appendix. In the separation of crystals and powder the solution was allowed to stand over night; the crystals were then collected on a small filter, and the solution allowed to run off to the last drop, before the crystals were washed with water, until the filter and filtrate were perfectly colourless. The filtrate was then diluted to 600 c.c., and after two hours' standing the powdery precipitate was also collected on a filter; both crystals and powder were then treated with potassium permanganate and potassium hydrate.

I have long adopted an increased addition of water, but for a different reason than the one now stated by Messrs.

1. 114 275-279 66 272-275 48 not at 300

Drops of 5 p.c.
Potassium

Permanganate.

153 20

12 4 12

II. 20 2 274-276 16'3 273-275 37 not at 300

93 10

62 6

10 3 12

625

10 4 16

278

277

260 80 256-258 278 36 270-274

82 7

CHEMICAL NEWS,

{ Oct. 27, 1876.

Meister, Lucius, and Brüning. I have always doubted the accuracy of adding 1 per cent of quinon, supposed to be retained in solution, and I have satisfied myself on that point by actual experiment. I have frequently evaporated the green solution to perfect dryness, and exhausted the dry powder with benzol and alcohol, but I have never succeeded in separating real quinon. The larger quantity of water merely separates the powder more completely, which no doubt accounts for the increased quantity of potassium permanganate used with the powder.

The conclusions drawn from this table, I may state as follows, viz. :—

1. The total of crystals and powder in all cases very nearly agrees with that of the mixture; no loss is incurred by the separation.

2. The melting- and solidifying-point of the mixture,
i.e., of the usual test, is mostly suspicious, in many
cases a direct indication of undoubted impurity of
the quinon.

3. The melting- and solidifying-points of the crystals
alone are much more uniform; the product is pure
quinon.
4. The powder in almost all cases is no quinon at all;
in eleven cases out of thirty it does not melt at
300° C., but blackens and remains solid; in eleven
other cases the mean of the two points is below
270° C., and in several of the other cases the
melting- and solidifying-points were only partial or
indistinct at the points indicated.

5. The effect of potassium permanganate is uniformly
very trifling upon the crystals, very considerable
upon the powder, and exactly the same is the case
with potassium hydrate; while the mixture often
imparts distinct colouration to the solution and
becomes itself lighter in colour-from orange to
pale straw-yellow-the crystals alone scarcely show
any change, but the powder invariably gives a
strong colour to the solution.

6. While the crystals may safely be taken as pure quinon, the question arises whether the powder always consists of nothing but impurities, or whether it still retains some quinon, as in a few cases the melting point tends to indicate.

Although I have not completed my experiments in that direction, I shall shortly be able to definitely settle this point by practical tests.

But I think it advisable not to delay the publication 83 10 of my results hitherto obtained, as I am satisfied of the correctness of separating crystals and powder and of its undoubted advantage over the other known test.

10 4 14

I have meanwhile brought my test into practical work22 6 20 ing by taking the crystals as pure quinon, and by considering the powder as valueless impurity in all cases where the melting- and solidifying-point is below 270° or above 280°, and by adding the powder to the crystals as quinon whenever these two points range between 270° and 280'.

16 5 18

12 5 16 82 8

10 3 12

IO 2 10

This compromise, for such I admit it to be at the best, has given general satisfaction to those who had it tried; and although I hope in a short time to complete my inves tigation, I meanwhile propose the above test, which, briefly

stated is as follows:

Boil 1 grm. of the sample for four hours with 15 grms. 9 3 10 of chromic acid dissolved in 10 c.c. of glacial acetic acid and 10 c.c. of water; allow it to stand for twelve hours, collect the crystals on a small filter, and let the solution run off to the last drop; then wash the crystals with boiling water till the filter and filtrate are quite colourless, dilute the filtrate with water to 600 c.c., let stand for two hours, and collect the powdery precipitate on a filter and wash well. Then treat both crystals and powderseparately, of course-with potassium permanganate and 12 2 14 potassium hydrate as hitherto, collect each on a double filter, dry and weigh, but do not add the correction; then take the melting- and solidifying-point of both. The

16 4 16 16 3 16

10 3 12

NEWS

crystals to be taken as pure quinon, the powder also to be taken as quinon if melting- and solidifying-points range between 270° and 280°, but as valueless impurities if these two points are below 270° or above 280°.

This test is more reliable, and more just to buyer and seller, than either the usual quinon test or the one now proposed by Messrs. Meister, Lucius, and Brüning. My experience as to the action of sulphuric acid upon crude quinon is as follows.

(To be continued.)

NOTES OF WORK BY STUDENTS OF PRACTICAL CHEMISTRY

IN THE

LABORATORY OF THE UNIVERSITY OF

VIRGINIA.

No. V.

Communicated by J. W. MALLET, Professor of General and Applied Chemistry in the University. (Continued from p. 169.)

(3.) On the Chemical Character of the Pigment of the Negro Skin. By Dr. F. P. FLOYD, of Tazewell Co., Virginia.

It is natural to suppose that the substance which gives the characteristic black colour to the skin of the negro is probably modified blood pigment, as is pretty generally assumed to be the case in reference to the "melanin" of the choroid coat of the eye; but this point does not seem to have been made until now the subject of experiment. I suggested to Dr. Floyd to examine qualitatively the character of the pigment in question, and to get, if pos sible, some approach to a determination of the amount of iron in the ash as the means of testing the probability of a connection with hæmatin.

Strips of cuticle with a little of the outer layer of true skin attached were taken from a negro cadaver, and having been well washed with water and alhohol, and with ether to remove fatty matter, were cautiously scraped with the blunt edge of a scalpel, in order, if possible, to loosen up the pigment granules and permit of their separation and purification by mechanical washing. A very little examination with the microscope, however, showed that this could not be done without breaking up the whole substance of the cuticular tissue, and mixing its débris with the granules, which therefore could not be obtained in a state of purity. By selecting only those parts in which there was most pigment, and cautiously treating these as above, enough of it was procured with but little admixture to establish the following points. The colouring matter is insoluble in water, alcohol, and ether. It is also undissolved by treatment with dilute acid or alkaline solutions. It is but slowly attacked by the strong acids, even by concentrated nitric acid. Chlorine, especially in the presence of alkalies, completely destroys it. Heated for some time with a strong solution of sodium hydrate it is gradually dissolved. and the solution when diluted yields a partial precipitate on neutralisation with an acid. In all these respects the behaviour of this substance agrees perfectly with the melanin of the eye.

In order to get an approximation to the quantity of iron present, as the pure pigment could not be had, comparative experiments were made with the cuticle of black and white subjects with the following results:

No. 1.-Skin from the outside of the upper arm of a Negro man, aged about 50 years, born in United States.— The cuticle and a little of the outer portion of the cutis were taken, washed with water and alcohol, macerated in ether for twenty-four hours to remove fat, and then dried at 100° C. 21 249 grms. of the dry material on being carefully and completely burned left 0'424 grm. of ash

=2'0 per cent. This ash was dissolved in a very small quantity of sulphuric acid, the solution diluted, and the iron (easily diluted in previous quantitative experiments) reduced to a ferrous salt by a minimum of pure zinc, determined by a much diluted solution of potassium permanganate. The result was 0.00859 grm. of Fe per cent of the ash.

=

=2'02

No. 2-Skin from the outside of the thigh of a Negro woman, aged about 40 years, born in Virginia. - The cuticle was rather more completely separated from the true skin than in the last instance. The same trea ment was applied. 2 grms. of material dried at 100° C. left 0'056 grm. of ash 2.8 per cent, and in this there was present o'00142 grm. of Fe = 2'54 e cent of ash. These specimen of negro skin were obtained from the Anatomical department of the University of Virginia; for those from white subjects, which at the time were not available here, we were indebted to my friend Dr. Souchon, of New Orleans.

No. 3.-Skin from the anterior surface of the thigh of a white man, 40 years of age, born in Maine.-The epidermis was taken off pretty clearly, with very little of the true skin remaining attached to it. Same chemical treatment as above. 18 grms. of the dry cuticle gave 0'207 grm. of ash 115 per cent, in which was found Fe = 0'00235 grm. = 1'13 per cent of the ash. No. 4.-Skin from anterior surface of upper portion of thigh of a white man, aged 45, born in France.-Cuticle taken off as clearly as possible and treated as before. 15.354 grms. of dry skin gave 0175 grm. of ash I'14 per cent, yielding o'00226 grm. of Fe 29 per cent of the ash.

-

=

It appears from the mean of these results that the negro cuticle leaves on being burned double as much ash as that of the white man (2:40 per cent against 115), and that the difference is nearly as great in the percentage of iron in the ash (2.28 against 1.21), thus rendering the presence of a considerable amount of iron in the black pigment highly probable, and increasing the likelihood of this being a product of the alteration of the colouring matter of the blood.

As regards the local distribution of the pigment granules there seems to have been hitherto a little confusion of statement. In the older books they are said to occur in the "rete mucosum" between the epidermis and cutis, and, although the existence of such a distinct middle layer of the skin is no longer admitted and the name for it has therefore disappeared, the same general idea seems to remain that the colouring matter belongs to the subcuticular portion of the skin, and hence impliedly that it does not extend outwards into the cuticle itself. I have found too in the Southern States many physicians under the impression that a blister produced upon the negro skin is white, or at any rate much lighter in colour than the surrounding surface. From the chemical inalterability of the pigment, as above ascertained, this would seem very unlikely; a few observations were therefore made upon the subject.

Thin vertical sections of negro skin from the cadaver were made, and these under the microscope showed brown and black granules to the very edge of the cuticular surface, which, however, seemed to have been partially removed, probably by post mortem softening and the washing which the subject had received.

A few extremely thin horizontal shavings were therefore taken off with a razor-like scalpel from the arms of two living negroes, man and woman respectively, drawing no blood and cutting with the blade so slanted as to thin off one side of the shaving to nothing. These sections showed under the microscope the pigment granules through the whole of the cuticle, though less easily observed among the epidermic scales than in the less dense structure beneath in which the flattening of the cells had not yet gone so far. Finally, one or two small blisters were produced by very small drops of a solution of cantharidine, and the raised cuticle from these gave quite th