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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
having the bottom and sides well covered with glue, the VOL. XXXIX. No. 1021.
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.
This very strong apparatus has not yet been much tried,
but before it was got a series of trials was made, by DETECTION OF FIRE - DAMP.
which it seemed certain that less than 5 per cent of marshBy Dr. R. ANGUS SMITH, F.R.S. &c.
gas 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-darnp, marsh.gaz, 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
The amount of gas detected is not minute, but it is a quancause it to heat and ignite a piece of tinder. The tube tity which will not explode, or flash, or spark, unless under used to be made of glass, but lately a method, inferior as I such exceptional circumstances as are here mentioned. It think, since the action becomes hidden, is employed, and would be quite safe to make this explosion in any atmothe compression is made in a brass tube. A piston, which sphere, as the flash is confined to the tube, and a man fits well, is put into the tube, and driven down rapidly could go in the dark and, as it were, feel the state of the by a blow with the palm of the hand on a smoothly air by making a spark as he went along. The apparatus rounded piece of wood at the top. As it was important needs nothing to be renewed except the air within. The to see the effect directly, a glass tube was necessary, and piston must be taken out and care taken to bring in a various substances were subjected to the heated air, so as fresh supply of air to be tried. The mode of doing this to obtain a little experience as a beginning. There was must have some attention. It must not be done by 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. Charcoal. putting a fire tube into the cylinder and sucking out the dust ignited readily without special preparation. Minuto air that had been compressed, and so letting fresh air in. quantities of gun-cotton at first did not take fire, and It might also be done by having a stopcock below and made the experimenters too bold, which ended in the letting the air in by that method, but the difficulty of shattering of the tube, which was 7 m.m. thick, and keeping the joints tight is remarkable. The use of a 6 m.m. internal diameter. When there was uncertainty loose plunger of wood to drive out the air is probably the trial was made in the dark, and it was found that the easiest. The blow has a wonderful power. The when a good lubricant was obtained there never was a cylinder and piston are only 8 m.m. in internal diameter, failure; a spark was elicited readily. Coal-dust gave and the compression is more than thirty atmospheres, many sparks; ether fired readily, and a mixture of coal about 420 lbs. on the square inch. gas and air exploded, bursting also more than one tube. It happened, however, that in trying the lubricant to see
Another method has gained my attention. Some time if the piston went down with ease, common air only being ago Mr. Ansell proposed to find the influx of fire-damp used, there was still a spark, and at last when the appa- well-known law of the diffusion of gases, the marsh-gas
into the air of mines by using its diffusive power. By a ratus was in good order one was obtained on every occasion. It seemed clear that the olive oil used for lubrica.
or fire-damp will pass into a porous vessel, if filled with tion was itself ignited. There were flashed alcohol, ether,
common air; and if the covering is of caoutchouc the turpentine, charcoal powder, coal powder, cotton-wool, pressure will raise it. The rise of the cover may be used olive oil, Young's lubricating oil.
for making a communication with an electric bell, and The work, which had been at first difficult, had become this is the method Mr. Ansell used.* at last too easy. The next step was to seek a non-com
The action is very rapid, but the raised caoutchouc bustible lubricant, and for a time a thick emulsion of oil
Besides this the air inside requires to be and soft soap was used. This did not give any sparks heavier than the outside gases which are expected to alone, but the use of water is an objection.
It would be necessary to keep a supply of this air glass 'tube, such as is sometimes sold
for the compression; I did not obviate this difficulty, but designed simply the
in order to make the apparatus self-acting, as it was intended. was shattered by one of the gas mixtures. For small explosions thinner tubes were used, it m.m. in thickness mode of filling the vessel with nitrogen, a gas nearly of
the same specific gravity as air. When the experiment of glass. Eventually this glass tube was put within a brass one o-5 m.m. thick, in which was a window to allow and passed into the air to be tried. The pressure at once
was to be made the vessel was filled with the nitrogen, the spark to be seen. Even this glass tube was shattered, giving way at the window, and bulging out the brass began within from the entrance of the lighter gas, and when 20 per cent of marsh-gas was added and exploded. it raised a needle which was made to magnify the move
ment considerably. I decided to have a much stronger tube, and that now
This apparatus required, first, a solution of chloride of made is unnecessarily thick. The glass is used only
These mixed gave for about two inches at the bottom, and as the diameter ammonium, next, chloride of lime.
the nitrogen, which was made to pass into the vessel with must be at least as great as that of the brass it is neces
the expansible cover. The pointers required some steady sary to put it in from below. To effect this a cap is made to screw upon the larger tube ; this cap contains the place on which to point, and the whole required a box. glass tube, part of which forms the glass of the window. The plan was not found convenient, and it did not indicate The screw is fin. long, so as to hold well. The glass under 5 per cent of marsh-gas as it was tried, but by must not be closed below by the blowpipe, as a blow upon varying the apparatus it could certainly be made to indi.
cate much less. Such an apparatus may in some cases the conical base, or even a base of any shape, readily breaks it, and the piston may at times go quite to the be found useful, and I give an account of it for that bottom. The airtightness must therefore be produced by
A full description of the apparatus alluded to will be found in the a good stuffing between the glass and the brass as well as Chemical News, vol. xii., p. 280, by Mr. George Frederick Ansell.
June 20, 1879. The first mentioned is certainly the handiest ON NITRIC NITROGEN IN GUANO.* when people require to move about, and the experiment
By ROBERT R. TATLOCK, F.R.S.E., F.C.S. 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,
Part I. which the late Lord Kinnaird, a lover of everything that from the results of some experiments which I made many promised good to the working classes, was very desirous years ago, I was led to the conclusion that a large proof introducing as a common instrument in coal mines.
portion—in some cases nearly the whole-of the nitrogen existing as nitraies 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 READY METHOD FOR PREPARING DIPHENYL.
am aware, even up to the present time, of preventing the By WATSON SMITH, F.C.S., F.I.C.
conversion, in presence of organic matter, of a very in. definite but always large proportion of the nitric nitrogen
into ammonia, it follows that all determinations of the By the adoption of the following method I have fonnd that latter made in guano are inaccurate unless they are a rich yield may be obtained of the above hydrocarbon, based upon the complete decomposition of the nitrates and the experiment is easily carried out, proceeds rapidly, with production of ammonia from the whole of their and without any danger. 62.4 grms. of benzene are nitrogen; and I am not aware that up till now this has mixed in a flask with 52 grms. of tin tetrachloride, or at been accomplished, or even the necessity for it admitted. least this proportion is observed, and the mixture is poured The amount of error will depend chiefly on the ratio of little by little into a dropping.tube, which allows it to fall the nitrates to the organic matter present, but will also drop by drop. into a tube of Bohemian glass, itself lying be much influenced by the nature of the latter as well as in a combustion-furnace, and maintained at a bright red by the completeness or otherwise of its admixture with heat. The combustion-tube should be bent at the outlet, the subject of the analysis. As it is not uncommon for almost at right angles, so as to pass through a cork fitting natural guanos to contain from 1 to 2 per cent of nitrates, into a wide-necked bottle. A tnbe passes from this bottle the error due to partial or imperfect decomposition of to another large bottle containing some water and also a the latter is considerable, but in the case of guanos or quantity of blotting, or filter-paper. This arrangement artificial manures which have been purposely mixed with serves to partially condense the hydrochloric acid evolved, la 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 the last named substance has been employed, the error gas. There is no need to pass the evolved gases through may and probably will be as great aš i per cent of à Licbig's condenser, for if a bright red heat be maintained ammonia-to the low side if it be assumed that the not more than one drop of undecomposed benzene would whole of the nitric nitrogen is obtained as ammonia, and be condensed, the above weights being taken. The di- to the high side if it be assumed that none of is obtained, phenyl is found mixed with stannous chloride in the in that form-in which case it is of course determined by a receiver in solid masses. Separation is easily effected by separate process and added tu the result obtained by the or. warm concentrated hydrochloric acid, which dissolves the dinary combustion with soda-lime. I was surprised to learn, stannous chloride, and leaves behind diphenyl. The latter recently, that the latter was the practice of chemists who is purified by distillation alone, and finally with steam. had had a very large and varied experience in agricultural
In a paper read before the Chemical Society, and pub, analyses, and the effect of it is that purchasers of guanos lished in the Fournal (July, 1876, and November, 1877), I and manures containing nitrates either naturally, or recommended distilling the contents of two flasks into artificially introduced, on the basis of their analyses, the red-hot tube, one containing the tin tetrachloride, the must pay for a large proportion, and in many instances other the benzene, and so that the vapours of the benzene practically the whole of the nitric nitrogen twice over. It passed through the flask containing ihe tin tetrachloride is possible that this practice, erroneous as it is, has arisen heated up to boiling. I now find that the method above from the circumstance that when nitrates are heated to recommended is much safer and easier of execution.
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 Widmannstetten's Figures on Artificial Iron.-J. amount according to the nature and proportion of the Lawrence Smith.—These figures, developed by the action organic substance and other circumstances. Being desirous of an acid upon a polished surface, have been considered of obtaining some reliable method by which the whole of characteristic of meteoric irons, some of which, however, the nitrates could be converted into ammonia during the do not show these figures. The author has succeeded in
* A Paper read before the Newcastle-upon-Tyne Chemical Society producing them upon silicide of icon.—Comptes Rendus. March 27, 1879.
Nitric Nitrogen in Guano.
269 Quantity of Organic Quantity of KNO, Ratio of Organic Weight of (NH), Percentage of Nitric Substance used.
used. Substance to KNO3. Pt. Čle obtained. Nitrogen obtained. Grammes. Grammes.
50*74 0:6 0.6 0'2
26'38 0:3 02 1-I
63'35 0:6 01
86'07 3'0 OI
97:40 0:8) O'I
combustion, and as it seemed hopeless to expect to find
Per Cent. any means of preventing the production of ammonia, to
( Phosphate of ammonia
14'29 a large extent, from them, in presence of crganic matters
Phos. mag. and ammonia..
1930 such as are invariably present in guano, I undertook the
Chloride of ammonium following series of experiments with the object of de
Sulphate of potash termining the effect of organic matters of different kinds WATER Sulphate of soda
4:81 and in different proportions in the production of ammonia
Nitrate of soda ..
I'55 from alkaline nitrate, in the ordinary combustion process
( Chloride of sodium
5'74 by soda-lime.
Phosphate of lime (tribasic) 14'91 In the trials made with starch the necessary correction INSOLUBLE IN Carbonate of lime
3'77 was made for the organic nitrogen naturally present WATER. Carbonate of magnesia
2.64 (which was found to be oʻ10 per cent) before the results
Sand .. were recorded in the table.
21:34 The combustions were made in the ordinary way, 40
15'77 grammes of soda-lime being employed in each case, the ammonia collected in dilute hydrochloric acid contained in nitrogen bulbs, as usual, and weighed as chloro-platinate
Soluble phosphoric acid..
7'11 of ammonium. The organic inatier was intimately
Equal to tribasic phosphate of lime 15:33 ground with the nitrates; this mixture was then first
Insoluble phosphoric acid ..
6.83 ground with a portion of the soda-lime, and ihe result well
Equal to tribasic of phosphate lime
14'91 mixed with the reniainder. (See above.) It will be seen from this table that the following con. Total phosphoric acid
13'94 clusions are deducible from these experiments :
Equal to tribasic phosphate of lime 30'44 1. That using 3 of organic matter (starch) to i of Nitrogen in ammoniacal salts
5.83 nitrate, 45'30 per cent of the nitric nitrogen can
Equal to ammonia
7.08 be obtained.
Nitrogen in organic matter (potential) 1:43 2. That in no case was the whole of the nitric nitrogen
Equal to ammonia
1973 converted into ammonia, the greatest proportion Nitric nitrogen (in nitrate)
0'25 being 97.40 per cent.
Equal to ammonia
0:31 3. That the results are somewhat variable even with the same proportion of the ingredients, something Total nitrogen
7:51 always depending on the completeness with which
Equal to ammonia
9:12 the mixture is made.
With regard to the best methods for the determination It will readily be conceded that in guanos where the of the nitric nitrogen in guanos there is still a great proportion of organic matter to nitrates is very high, as difference of opinion. Methods based upon the liberation is the case in ammoniacal guanos, it is quite erroneous of nitric acid, and the determination, direaly, of the to determine nitric nitrogen by a separate process and oxidising power of the liberated acid, are erroneous and add it to the nitrogen obtained by combustion with soda. misleading, fror. the fact of the well-known action of lime, it being already included therein. It follows from nitric acid, especially when largely mixed with strong this consideration and from these experiments that it sulphuric acid upon soluble organic matters such as are is best to conduct the combustion in such a way as to always present in ammoniacal guanos. The indigo convert as much as possible of the nitric nitrogen into method of Boussingault is an example of these, although ammonia, and that if it is determined separately in order it is recommended by experts in agricultural analyses ; to distinguish it from that existing in other forms, it and that of Harcourt, by distilling with zinc, iron, and should not in these circumstances be added to the ni. caustic alkali, although a minutely accurate one for trogen, in which it is already included.
estimating nitrogen, when properly applied, as I can The following detailed analysis which I have made testify from a long experience of it, is not applicable to of a sample of " Huanillos ” guano will serve to show, guanó on account of the solublue nitrogenous matters by observing the ratio of the organic matter to the nitrate, always present, and which even permanganate of potasthat at least one-half, probably much more, of the nitrogen sium only partially destroys. Yet tliis method is recom. contained in the nitrate will be estimated in the process mended by skilled analysts, with the sole precaution of of combustion :
removing the ammoniacal salts before applying it,
June 20, 1879. 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 con- length of time until all is of a dark green colour, and subsequence of employing this method in conjunction with sequently passing them through a warm bath of soda, the practice of adding the nitric nitrogen to that obtained which develops the black in a short time. Instead of the in the combustion process is that part of the nitrogen is soda-bath, a bath with small quantities of chrome and stated, and consequently paid for three times, the organic hydrochloric acid develops a much deeper and finer black, nitrogen being inadvertently determined with the nitric which does not turn green.
en, and both added to the nitrogen obtained by com- Of course there are nearly as many modifications of this bustion, which already contains both.
method of dyeing as there are dyers, colourists, and chePelouze's method, based upon the oxidation of ferrous mists, who have been trying it, and have modified the salts by the liberated nitric acid, in an aimosphere of original process with a view to improve upon it, many of carbonic acid, I have found to give good results in some them succeeding to a certain extent, but none completely. cases ; but they are no doubt too low where much soluble The introduction of vanadium in these processes (which organic matter is present, even if the latter be removed as is not new, as the late Mr. John Lightfoot mentioned it in far as possible by permanganate of potassium.
his Patent specifications) was certainly a great improve. Crum's process (Proceedings of the Philosophical | ment, but even with its aid it was impossible to overcome Society of Glasgow, 1848, p. 162), besides being a really the difficulties in dyeing mentioned above. Even supposing scientific one, and capable of great accuracy, is free from these difficulties had been overcome, the process of dyeing the objection of giving too low results in presence of soluble Lightfoot-black would be a very tedious one on account organic matter; for although the latter is acted upon by of the length of time needed for the development of the the nitric acid, it is a matter of indifference what reduces green colouration and the great number of baths the goods the latter if only nitric oxide be produced, by the measure- would have to pass. ment of which the nitric nitrogen is estimated. It seems The Lightfoot-blacks can be divided into those which necessary, however, to prove, where organic matter is turn green by exposure to air, and those which remain present, that the evolved gas consists entirely of nitric black under the same circumstances. The first are the oxide, as a little nitrogen sometimes appears, probably as common and the second the oxidised Lightroot-blacks. a result of the action of the strong sulphuric acid on The shades of these series of blacks run from blue, dark blue, nitrogenous organic matter. This can easily be done, as bluish-grey, blue-black, grey, and black to brown-grey and Crum describes, by introducing into the nitrometer some brown-black, and even to brown and black-brown. warm solution of iron sulphate, observing the amount The first link of these series is the blue which the late of gas absorbed and regarding this only as nitric oxide. Dr. Crace-Calvert invented and obtained by the action on
I am at present endeavouring to obtain the perfect re- aniline hydrochloride with a smaller quantity of potassium solution of the nitric nitrogen into ammonia, and am chlorate than for black, and some ferrous sulphate in order also conducting some experiments with the view of finding to moderate the oxidation. Next to this blue ranges the method best adapted for estimating nitric nitrogen in Lightfoot's blue-black, and then follow the other shades in guanos and manures.
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 ON THE DIFFERENT ANILINE-BLACKS.*
varying from reddish brown to yellowish brown, which By JUSTUS WOLFF.
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 conIn the first instance there are two different series oftains-ihe bluer is the black produced by that process, thus aniline-blacks, viz., those which are produced in or on the showing that the brown colouring matter accompanying fibre, and those which are manufactured first and then the blue in the Lightfoot-blacks owes its origin to toluydin applied to the fibre by the usual dyeing process.
contained in the commercial anilines, even if only in small The first-named series were invented by the late Mr. quantities. John Lightroot, of Accrington, in the year 1866, and are Some metallic compounds-as, for example, of copper, extremely well adapted for printing black on vegetable cerium, vanadium, and certain others have the property tissues, being in some cases the best black-print out. to deepen this dark blue to a very fine blue-black, even if
Many various fruitless and expensive efforts bave been employed only in small quantities, by their ability to in. made to dye fibres and fabrics by the Lightfoot process crease the strength or power of oxidation. and its improvements, but have failer, although the shades The stronger the action of oxidation, up to a certain of the black produced by some of the methods in these degree, on the aniline or the aniline sale the darker beseries are extremely beautiful.
comes the product of that oxidation, whilst the weaker the The greatest difficulty in dyeing according to Lightroot's action of oxidation the bluer the shade obtained. On this process is to get the shades evenly distributed over the principle a blue or black can be produced from the same fibres and fabrics, and it has not yet been overcome satis. quality of aniline. factorily, although many experiments on a very large scale As to the chemical constitution of the Lightfoot-blacks have been made for that purpose in Bradford and Man- not much is known, and the investigations made to that chester dve-works with cotton goods.
purpose have not yet thrown much light on that dark The difficulties in dyeing worsted and silk tissues by object. these and kindred processes in even shades are still greater, According to Reinbeck's results of research, the Lightand that is the reason why this beautiful and fast dye is foot-black is a powerfui base of violet-black colour, forming not produced on yarns and fabrics on a large scale except with acids green coloured compounds. by printing on cotton, in which application it far sur. A. Müller's formula of Lightfoot-black, as the result of passes all other black print by beauty of shade.
direct elementary analysis, C12H14N2011, is an improbable The methods of dyeing yarns and woven fabrics accord- one on account of the large proportions of hydrogen and ing to the Lightfoot process consist principally in soaking oxygen. Without regarding this last-named defeat, the them thoroughly and evenly in a strong solution of aniline proportion of carbon and nitrogen would allow us to conhydrochloride, with or without free aniline, and potassium sider it as a derivative from diphenylen-diamin by chlorate, with or without the addition of other-especially powerful oxidation. metallic-compounds, afterwards exposing the goods A more reliable elementary analysis published by
Goppelsræder (Dingler's Polytechnisches Journal, ccxxiv., * All temperatures are given in Centigrades.
439 to 448) leads to the empyric formula C24H20N4 for the
COHEN — N(CH3)
271 common Lightfoot-black; he interprets in it the folo, Orlowing ways
C6H4-C6H4 1. (C6H3)N-(C6H5)N-(C6H3)N-(C6H5) Y
Turning now to the other aniline-blacks, viz., those
which are manufactured from aniline first, and then when of which he considers the first as the most probable one.
ready are applied to the fibres by the usual dyeing process, The chemical constitution of the oxidised black is, then, the names used for them in commerce, viz., indulin and
we meet with two series, which we will keep distinct by (C6H3)N –(C6H3)N-(C6H3)N-(C6H3)N
The name nigrosin I gave to that series of black which
I invented in the year 1862, in the laboratory of Messrs. (C6H3)N-O-N(C6H5)
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. Whilst the reduced common black he represents
The first link of the indulin series I found out in 1865 HN(C6Hp) – N(C6H3)-N(C6H3)-(C6H5NH,
by treating the bases of magenta-refuse with aniline and
acetic acid, a process very similar to that of the production (C6H3)N-N(C6H5)
of aniline-blue from magenta. The spirit-soluble indulin
produced by that process was converted with oil of vitriol (C6H3)N N(C6H5)
into the water-soluble indulin, fradulently called by some
firms nigrosin. H H
The indulins are manufactured in several ways; first With potassium bisulphate he produces naphthalin-pink
from magenta refuse :from the Lightfoot-black:
The refuse is treated with boiling water containing hy.
drochloric acid in order to extract the salts of mauvanilin, 5(C24H20N.) +16HKSO4=
rosanilin, and chrysanilin completely, ard to leave the
Naphthalin pink. violanilin salt undissolved, which is decomposed with caustic =8N+ 16H20+8502+8K2S04+4C30H21N3), soda, and by this treatment the violanilin base is obtained wherein the following decomposition of potassium bi- in a free state. To convert this violanilin (or also mixtures sulphate takes place :
of bases containing it in the largest proportion), a mixture 2KHSO4= K2S04,H20+0+S02.
of say, 10 parts dry violanilin, 6 parts commercial acetic
acid (of the equivalent 120), and 20 parts aniline for blue, Another author produces by treatment of Lightfoot's is heated to between 140° to 160° as long as ammonia is black with aniline a fine aniline-pink of the formula- developed, and till the mass dissolves in alcohol (acidulated C36H33N5.
with acetic acid) in the desired shade. Arrived at that: These investigations have been made on the aniline- state, the excess of aniline is liberated by addition of black produced by electrolysis, which is identical with the caustic soda sufficient to neutralise the 6 parts of acetic Lightfoot-black. All these formulæ of aniline-blacks acid (which are in the mixture), and driven off by a current show that they are the products of a powerful oxidation of steam. The indulin base thus obtained is separated simultaneously with a considerable condensation.
from the solution containing acetate of soda, washed, It is very probable that in Lightfoot-black a connection powdered, and dried, and may be used in that state directly of nuclei has taken place (an interpretation supported for conversion into the water-soluble state; but it may by the production of naphthalin-pink with bisulphate of also be purified by treating it several times with boiling potassium, as stated by Goppelsræder, by the property to acidulated water in order to obtain the salts of the indulin form products of substitution with aniline,-aniline-pink- bases, which also have to be dried before conversion. This and also by some analogies coming forth in the course of conversion is effected in the following manner :this paper), which leads to the following formulæ for Light- Into three or four parts of oil of vitriol of 66° B., or, if foot's black ;
needed, of fuming oil of vitriol (Nordhausen vitriol oil), or C6H4-C6H4
mixtures of both, heated up to about 100°, one part of dry
indulin base or its salts is given in slowly whilst the liquid H-N N-H
is well agitated. When all is in the heat is raised to about III. |
120° to 140°, and kept there for such a length of time H-N N-H
(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°, disThe oxidised black
solves quickly and completely. This point reached, the C6H4-C6H4
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 IV.
hours, the water drawn off, and the sediment repeatedly H-N N-H
washed in this way with fresh quantities of water till it
produces no perceivable sour taste. Then it is filtered and CH, CH,
boiled with caustic soda solution, just sufficient to dissolve
it and to form a neutral salt, and then dried down at a The reduced Lightfoot-black
temperature not higher than 70°. Sometimes in place of H H H
H soda ammonia is used. It forms then the water-soluble
indulin. Y. N-C6H4-C6H4-N-N-C6H4-C6H4-N Another way to produce indulin is by heating a mixture
of 10 parts aniline (possibly pure preferred) with 20 parts H
of syrupy arsenic acid (containing 70 per cent of dry