NEWS

on the screw. The glass is covered with an india-rubber

THE CHEMICAL NEWS. tube, and the two are put into the brass tube, previously

VOL. XXXIX. No. 1021.

DETECTION

OF

FIRE-DAMP.

By Dr. R. ANGUS SMITH, F.R.S. &c.

having the bottom and sides well covered with glue, the best substance for this yet found. A mixture of resin and wax (and even caoutchouc if dry) was itself ignited by the improved mode to be mentioned.

The amount of gas detected is not minute, but it is a quantity which will not explode, or flash, or spark, unless under such exceptional circumstances as are here mentioned. It would be quite safe to make this explosion in any atmosphere, as the flash is confined to the tube, and a man could go in the dark and, as it were, feel the state of the air by making a spark as he went along. The apparatus needs nothing to be renewed except the air within. The piston must be taken out and care taken to bring in a fresh supply of air to be tried. The mode of doing this must have some attention. It must not be done by

This very strong apparatus has not yet been much tried, but before it was got a series of trials was made, by which it seemed certain that less than 5 per cent of marshgas could not be distinguished in air. In order to increase the delicacy of the process there was inserted a small amount of platinum-black, a very small amount is enough. THE detection of fire-damp, marsh-gas, or mine-gas, has The use of platinum I have had in view for several exoccupied many minds since the time that Sir Humphry periments in condensation of gases, and here it was Davy began his enquiries and invented his celebrated pre- found remarkably successful, bringing down the amount cautions. I have often thought of two methods of testing of marsh-gas to be detected to 21 per cent. On the other for the gas, but only lately had them really tried. The hand, it was necessary to use a lubricator without oil, so first is by the use of the small instrument called, unfortu- | that the friction is considerably increased; at present we nately, a compression syringe. It is commonly used for are using soap only. very rapidly compressing a small tubeful of air, so as to cause it to heat and ignite a piece of tinder. The tube used to be made of glass, but lately a method, inferior as I think, since the action becomes hidden, is employed, and the compression is made in a brass tube. A piston, which fits well, is put into the tube, and driven down rapidly by a blow with the palm of the hand on a smoothly rounded piece of wood at the top. As it was important to see the effect directly, a glass tube was necessary, and various substances were subjected to the heated air, so as to obtain a little experience as a beginning. There was no good tinder at hand, and cotton-wool in small quan-blowing as some might suppose, but it might be done by tities failed to ignite until it was well dried. Charcoaldust ignited readily without special preparation. Minute quantities of gun-cotton at first did not take fire, and made the experimenters too bold, which ended in the shattering of the tube, which was 7 m.m. thick, and 6 m.m. internal diameter. When there was uncertainty the trial was made in the dark, and it was found that when a good lubricant was obtained there never was a failure; a spark was elicited readily. Coal-dust gave many sparks; ether fired readily, and a mixture of coalgas and air exploded, bursting also more than one tube. It happened, however, that in trying the lubricant to see if the piston went down with ease, common air only being used, there was still a spark, and at last when the apparatus was in good order one was obtained on every occasion. It seemed clear that the olive oil used for lubrication was itself ignited. There were flashed alcohol, ether, turpentine, charcoal powder, coal powder, cotton-wool, olive oil, Young's lubricating oil.

The work, which had been at first difficult, had become at last too easy. The next step was to seek a non-combustible lubricant, and for a time a thick emulsion of oil and soft soap was used. This did not give any sparks alone, but the use of water is an objection. A strong glass tube, such as is sometimes sold for the compression, was shattered by one of the gas mixtures. For small explosions thinner tubes were used, 1 m.m. in thickness of glass. Eventually this glass tube was put within a brass one o'5 m.m. thick, in which was a window to allow the spark to be seen. Even this glass tube was shattered, giving way at the window, and bulging out the brass when 20 per cent of marsh-gas was added and exploded. I decided to have a much stronger tube, and that now made is unnecessarily thick. The glass is used only for about two inches at the bottom, and as the diameter must be at least as great as that of the brass it is necessary to put it in from below. To effect this a cap is made to screw upon the larger tube; this cap contains the glass tube, part of which forms the glass of the window. The screw is in. long, so as to hold well. The glass must not be closed below by the blowpipe, as a blow upon the conical base, or even a base of any shape, readily breaks it, and the piston may at times go quite to the bottom. The airtightness must therefore be produced by a good stuffing between the glass and the brass as well as

putting a fine tube into the cylinder and sucking out the air that had been compressed, and so letting fresh air in. It might also be done by having a stopcock below and letting the air in by that method, but the difficulty of keeping the joints tight is remarkable. The use of a loose plunger of wood to drive out the air is probably the easiest. The blow has a wonderful power. The cylinder and piston are only 8 m.m. in internal diameter, and the compression is more than thirty atmospheres, about 420 lbs. on the square inch.

Another method has gained my attention. Some time ago Mr. Ansell proposed to find the influx of fire-damp into the air of mines by using its diffusive power. By a well-known law of the diffusion of gases, the marsh-gas or fire-damp will pass into a porous vessel, if filled with common air; and if the covering is of caoutchouc the pressure will raise it. The rise of the cover may be used for making a communication with an electric bell, and this is the method Mr. Ansell used.* The action is very rapid, but the raised caoutchouc soon falls. Besides this the air inside requires to be heavier than the outside gases which are expected to enter. It would be necessary to keep a supply of this air I did not obviate this difficulty, but designed simply the in order to make the apparatus self-acting, as it was intended. mode of filling the vessel with nitrogen, a gas nearly of the same specific gravity as air. When the experiment was to be made the vessel was filled with the nitrogen, and passed into the air to be tried. The pressure at once began within from the entrance of the lighter gas, and it raised a needle which was made to magnify the movement considerably.

This apparatus required, first, a solution of chloride of These mixed gave ammonium, next, chloride of lime. the nitrogen, which was made to pass into the vessel with place on which to point, and the whole required a box. the expansible cover. The pointers required some steady The plan was not found convenient, and it did not indicate under 5 per cent of marsh-gas as it was tried, but by varying the apparatus it could certainly be made to indicate much less. Such an apparatus may in some cases be found useful, and I give an account of it for that

A full description of the apparatus alluded to will be found in the CHEMICAL NEWS, vol. xii., p. 280, by Mr. George Frederick Ansell,

268

reason.

Nitric Nitrogen in Guano.

The first-mentioned is certainly the handiest when people require to move about, and the experiment can be done in the dark; whereas this second plan needs a steady place and light. Still, it is sound in principle, and may be a useful supplement to Mr. Ansell's apparatus, which the late Lord Kinnaird, a lover of everything that promised good to the working classes, was very desirous of introducing as a common instrument in coal-mines.

READY METHOD FOR PREPARING DIPHENYL.
By WATSON SMITH, F.C.S., F.I.C.

By the adoption of the following method I have fonnd that a rich yield may be obtained of the above hydrocarbon, and the experiment is easily carried out, proceeds rapidly, and without any danger. 624 grms. of benzene are mixed in a flask with 52 grms. of tin tetrachloride, or at least this proportion is observed, and the mixture is poured little by little into a dropping-tube, which allows it to fall drop by drop into a tube of Bohemian glass, itself lying in a combustion-furnace, and maintained at a bright red heat. The combustion-tube should be bent at the outlet, almost at right angles, so as to pass through a cork fitting into a wide-necked bottle. A tnbe passes from this bottle to another large bottle containing some water and also a quantity of blotting- or filter-paper. This arrangement serves to partially condense the hydrochloric acid evolved,

ON NITRIC NITROGEN IN GUANO.*
By ROBERT R. TATLOCK, F.R.S.E., F.C.S.

PART I.

FROM the results of some experiments which I made many years ago, I was led to the conclusion that a large proportion-in some cases nearly the whole-of the nitrogen existing as nitrates in guano appears, and is estimated as ammonia, in the ordinary process of combustion with soda-lime. As there are no means known, so far as I am aware, even up to the present time, of preventing the conversion, in presence of organic matter, of a very indefinite but always large proportion of the nitric nitrogen into ammonia, it follows that all determinations of the latter made in guano are inaccurate unless they are based upon the complete decomposition of the nitrates with production of ammonia from the whole of their nitrogen; and I am not aware that up till now this has been accomplished, or even the necessity for it admitted. The amount of error will depend chiefly on the ratio of the nitrates to the organic matter present, but will also be much influenced by the nature of the latter as well as by the completeness or otherwise of its admixture with the subject of the analysis. As it is not uncommon for natural guanos to contain from 1 to 2 per cent of nitrates, the error due to partial or imperfect decomposition of the latter is considerable, but in the case of guanos or artificial manures which have been purposely mixed with a considerable proportion of a nitrate, such as nitrate of

but another tube passes from this bottle into a draught- | soda, it is much augmented, and if, say 10 per cent of place, or through a window, to lead off the uncondensed gas. There is no need to pass the evolved gases through a Licbig's condenser, for if a bright red heat be maintained not more than one drop of undecomposed benzene would be condensed, the above weights being taken. The diphenyl is found mixed with stannous chloride in the receiver in solid masses. Separation is easily effected by warm concentrated hydrochloric acid, which dissolves the stannous chloride, and leaves behind diphenyl. The latter is purified by distillation alone, and finally with steam.

In a paper read before the Chemical Society, and published in the Journal (July, 1876, and November, 1877), I recommended distilling the contents of two flasks into the red-hot tube, one containing the tin tetrachloride, the other the benzene, and so that the vapours of the benzene passed through the flask containing the tin tetrachloride heated up to boiling. I now find that the method above recommended is much safer and easier of execution.

Widmannstætten's Figures on Artificial Iron.-J. Lawrence Smith.-These figures, developed by the action of an acid upon a polished surface, have been considered characteristic of meteoric irons, some of which, however, do not show these figures. The author has succeeded in producing them upon silicide of iron.-Comptes Rendus.

the last named substance has been employed, the error may and probably will be as great as 1 per cent of ammonia-to the low side if it be assumed that the whole of the nitric nitrogen is obtained as ammonia, and to the high side if it be assumed that none of is obtained, in that form--in which case it is of course determined by a separate process and added to the result obtained by the or. dinary combustion with soda-lime. I was surprised to learn, recently, that the latter was the practice of chemists who had had a very large and varied experience in agricultural analyses, and the effect of it is that purchasers of guanos and manures containing nitrates either naturally, or artificially introduced, on the basis of their analyses, must pay for a large proportion, and in many instances practically the whole of the nitric nitrogen twice over. It is possible that this practice, erroneous as it is, has arisen from the circumstance that when nitrates are heated to redness with soda-lime, no ammonia is obtained; at any rate I have ascertained this by direct experiment. The result is very different, however, when organic matter is present, ammonia being always produced, varying in amount according to the nature and proportion of the organic substance and other circumstances. Being desirous of obtaining some reliable method by which the whole of the nitrates could be converted into ammonia during the A Paper read before the Newcastle-upon-Tyne Chemical Society March 27, 1879.

270

The Different Aniline-Blacks.

{CHEMICAL NEWS,

June 20, 1879.

length of time until all is of a dark green colour, and subsequently passing them through a warm bath of soda, which develops the black in a short time. Instead of the soda-bath, a bath with small quantities of chrome and hydrochloric acid develops a much deeper and finer black, which does not turn green.

although the inevitable result of its use is that the organic | in a moderately warm place to the action of air for such a nitrogen is included with the nitric nitrogen. The consequence of employing this method in conjunction with the practice of adding the nitric nitrogen to that obtained in the combustion process is that part of the nitrogen is stated, and consequently paid for three times, the organic nitrogen being inadvertently determined with the nitric nitrogen, and both added to the nitrogen obtained by combustion, which already contains both.

Pelouze's method, based upon the oxidation of ferrous salts by the liberated nitric acid, in an atmosphere of carbonic acid, I have found to give good results in some cases; but they are no doubt too low where much soluble organic matter is present, even if the latter be removed as far as possible by permanganate of potassium.

Of course there are nearly as many modifications of this method of dyeing as there are dyers, colourists, and chemists, who have been trying it, and have modified the original process with a view to improve upon it, many of them succeeding to a certain extent, but none completely. The introduction of vanadium in these processes (which is not new, as the late Mr. John Lightfoot mentioned it in his Patent specifications) was certainly a great improvethe difficulties in dyeing mentioned above. Even supposing these difficulties had been overcome, the process of dyeing Lightfoot-black would be a very tedious one on account of the length of time needed for the development of the green colouration and the great number of baths the goods would have to pass.

Crum's process (Proceedings of the Philosophicalment, but even with its aid it was impossible to overcome Society of Glasgow, 1848, p. 162), besides being a really scientific one, and capable of great accuracy, is free from the objection of giving too low results in presence of soluble organic matter; for although the latter is acted upon by the nitric acid, it is a matter of indifference what reduces the latter if only nitric oxide be produced, by the measurement of which the nitric nitrogen is estimated. It seems necessary, however, to prove, where organic matter is present, that the evolved gas consists entirely of nitric oxide, as a little nitrogen sometimes appears, probably as a result of the action of the strong sulphuric acid on nitrogenous organic matter. This can easily be done, as Crum describes, by introducing into the nitrometer some warm solution of iron sulphate, observing the amount of gas absorbed and regarding this only as nitric oxide.

I am at present endeavouring to obtain the perfect resolution of the nitric nitrogen into ammonia, and am also conducting some experiments with the view of finding the method best adapted for estimating nitric nitrogen in guanos and manures.

ON THE DIFFERENT ANILINE-BLACKS.*
By JUSTUS WOLFF.

In the first instance there are two different series of aniline-blacks, viz., those which are produced in or on the fibre, and those which are manufactured first and then applied to the fibre by the usual dyeing process.

The first-named series were invented by the late Mr. John Lightfoot, of Accrington, in the year 1866, and are extremely well adapted for printing black on vegetable tissues, being in some cases the best black-print out.

Many various fruitless and expensive efforts have been made to dye fibres and fabrics by the Lightfoot process and its improvements, but have failed, although the shades of the black produced by some of the methods in these series are extremely beautiful.

The greatest difficulty in dyeing according to Lightfoot's process is to get the shades evenly distributed over the fibres and fabrics, and it has not yet been overcome satisfactorily, although many experiments on a very large scale have been made for that purpose in Bradford and Manchester dve-works with cotton goods.

The difficulties in dyeing worsted and silk tissues by these and kindred processes in even shades are still greater, and that is the reason why this beautiful and fast dye is not produced on yarns and fabrics on a large scale except by printing on cotton, in which application it far surpasses all other black print by beauty of shade.

The methods of dyeing yarns and woven fabrics according to the Lightfoot process consist principally in soaking them thoroughly and evenly in a strong solution of aniline hydrochloride, with or without free aniline, and potassium chlorate, with or without the addition of other-especially metallic-compounds, afterwards exposing the goods

* All temperatures are given in Centigrades.

The Lightfoot-blacks can be divided into those which turn green by exposure to air, and those which remain black under the same circumstances. The first are the common and the second the oxidised Lightfoot-blacks. The shades of these series of blacks run from blue, dark blue, bluish-grey, blue-black, grey, and black to brown-grey and brown-black, and even to brown and black-brown.

The first link of these series is the blue which the late Dr. Crace-Calvert invented and obtained by the action on aniline hydrochloride with a smaller quantity of potassium chlorate than for black, and some ferrous sulphate in order to moderate the oxidation. Next to this blue ranges Lightfoot's blue-black, and then follow the other shades in the succession given above.

These blacks, in common with the other anilineblacks, are mixtures of at least two shades, viz., of a very deep blue and deep brown, the latter varying from reddish brown to yellowish brown, which quality enables it to produce many different shades of black in combination with the deep blue.

The purer the aniline-that is, the less toluydin it contains-the bluer is the black produced by that process, thus showing that the brown colouring matter accompanying the blue in the Lightfoot-blacks owes its origin to toluydin contained in the commercial anilines, even if only in small quantities.

Some metallic compounds-as, for example, of copper, cerium, vanadium, and certain others-have the property to deepen this dark blue to a very fine blue-black, even if employed only in small quantities, by their ability to increase the strength or power of oxidation.

The stronger the action of oxidation, up to a certain degree, on the aniline or the aniline salt the darker becomes the product of that oxidation, whilst the weaker the action of oxidation the bluer the shade obtained. On this principle a blue or black can be produced from the same quality of aniline.

As to the chemical constitution of the Lightfoot-blacks not much is known, and the investigations made to that purpose have not yet thrown much light on that dark object.

According to Reinbeck's results of research, the Lightfoot-black is a powerful base of violet-black colour, forming with acids green coloured compounds.

A. Müller's formula of Lightfoot-black, as the result of direct elementary analysis, C12H14N2O11, is an improbable one on account of the large proportions of hydrogen and oxygen. Without regarding this last-named defect, the proportion of carbon and nitrogen would allow us to consider it as a derivative from diphenylen-diamin by powerful oxidation.

A more reliable elementary analysis published by Goppelsræder (Dingler's Polytechnisches Journal, ccxxiv., 439 to 448) leads to the empyric formula Č24H20N4 for the

NEWS

common Lightfoot-black; he interprets in it the fol- | Orlowing ways.

I. (C6H5)N-(C6H5)N — (C6H5)N — (C6H5)N ̧

=

(C6H5)N-N(C6H5)
(C6H5)Ñ - Ñ(C6H5)

II. NH C6H4-NH-C6H4-
-C6H4-NH-C6H4
41

NH,

of which he considers the first as the most probable one. The chemical constitution of the oxidised black is, then,

Or,

(C6H5)N-(C6H5)N-(C6H5)N— (C6H5)N

O

With potassium bisulphate he produces naphthalin-pink
from the Lightfoot-black:-
5(C24H20N4)+16HKSO1 =

Naphthalin pink.

=8N+16H2O+8SO2+8K2SO4+4(C30H21N3), wherein the following decomposition of potassium bisulphate takes place :

2KHSO4 = K2SO4, H2O+O+SO2. Another author produces by treatment of Lightfoot's black with aniline a fine aniline-pink of the formulaC36H33N5.

These investigations have been made on the anilineblack produced by electrolysis, which is identical with the Lightfoot-black. All these formulæ of aniline-blacks show that they are the products of a powerful oxidation simultaneously with a considerable condensation.

It is very probable that in Lightfoot-black a connection of nuclei has taken place (an interpretation supported by the production of naphthalin-pink with bisulphate of potassium, as stated by Goppelsroder, by the property to form products of substitution with aniline,-aniline-pinkand also by some analogies coming forth in the course of this paper), which leads to the following formulæ for Lightfoot's black :

III.

C6H4-C6H4

The oxidised black

C6H4 -C6H4

Turning now to the other aniline-blacks, viz., those which are manufactured from aniline first, and then when ready are applied to the fibres by the usual dyeing process, the names used for them in commerce, viz., indulin and we meet with two series, which we will keep distinct by nigrosin.

The name nigrosin I gave to that series of black which I invented in the year 1862, in the laboratory of Messrs. Appold Frères, in Sulzbach, near Saarbrücken. But since then this name has been usurped by some firms for colouring matters belonging to the indulin series in order to sell an inferior article at the price of the real nigrosin. The first link of the indulin series I found out in 1865 by treating the bases of magenta-refuse with aniline and acetic acid, a process very similar to that of the production of aniline-blue from magenta. The spirit-soluble indulin produced by that process was converted with oil of vitriol into the water-soluble indulin, fradulently called by some firms nigrosin.

The indulins are manufactured in several ways; first from magenta refuse:—

The refuse is treated with boiling water containing hydrochloric acid in order to extract the salts of mauvanilin, rosanilin, and chrysanilin completely, and to leave the soda, and by this treatment the violanilin base is obtained violanilin salt undissolved, which is decomposed with caustic in a free state. To convert this violanilin (or also mixtures of bases containing it in the largest proportion), a mixture of say, 10 parts dry violanilin, 6 parts commercial acetic is heated to between 140° to 160° as long as ammonia is acid (of the equivalent 120), and 20 parts aniline for blue, developed, and till the mass dissolves in alcohol (acidulated state, the excess of aniline is liberated by addition of with acetic acid) in the desired shade. Arrived at that caustic soda sufficient to neutralise the 6 parts of acetic acid (which are in the mixture), and driven off by a current of steam. The indulin base thus obtained is separated powdered, and dried, and may be used in that state directly from the solution containing acetate of soda, washed, for conversion into the water-soluble state; but it may also be purified by treating it several times with boiling bases, which also have to be dried before conversion. This acidulated water in order to obtain the salts of the indulin conversion is effected in the following manner:

Into three or four parts of oil of vitriol of 66° B., or, if needed, of fuming oil of vitriol (Nordhausen vitriol oil), or mixtures of both, heated up to about 100°, one part of dry indulin base or its salts is given in slowly whilst the liquid is well agitated. When all is in, the heat is raised to about 120° to 140°, and kept there for such a length of time (about five hours) till a sample drawn and completely washed with water (in order to remove all free sulphuric acid), and treated with ammonia at about 60° or 70°, dissolves quickly and completely. This point reached, the solution of the colour in oil of vitriol is, whilst yet hot, poured into about five times its weight of clear cold water, which is well agitated, then settled for several hours, the water drawn off, and the sediment repeatedly washed in this way with fresh quantities of water till it produces no perceivable sour taste. Then it is filtered and boiled with caustic soda solution, just sufficient to dissolve it and to form a neutral salt, and then dried down at a temperature not higher than 70°. Sometimes in place of soda ammonia is used. It forms then the water-soluble indulin.

Another way to produce indulin is by heating a mixture of 10 parts aniline (possibly pure preferred) with 20 parts of syrupy arsenic acid (containing 70 per cent of dry