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ON NITROGEN IODIDE.

By J. W. MALLET.

THE various researches upon the highly explosive black substance formed by the action of iodine upon ammonia have, as is well known, led to diflerent views of its composition. That first put forward by Colin and GayLussac, namely that it is nitrogen tri-iodide, appeared to have been set aside by the experiments of Serullas,* Millon,+ Bineau, Gladstone, § Playfair, and Bunsen, all of whom found hydrogen to be a constituent, but in varying amount, the formulæ NHI2-NH2I-NH3.NI,and NH3.4NI3 having been assigned to the products obtained by somewhat different processes, until more recently Stahlschmidt has revived the statement that under certain conditions at least the simple tri-iodide is formed.

One source of error in the analysis of this instable compound seems to have received insufficient attention from some of those who have examined it, and somewhat affects the conclusions drawn from the experiments of others. The substance, obtained as a black powder by the action of iodine on ammonia, decomposes gradually in contact with water, nitrogen gas being slowly evolved, iodine liberated, and iodic and hydriodic acids or ammonium salts formed. This decomposition takes place to no inconsiderable extent during the drying of the powder at ordinary temperature, and may be readily proved to have occurred by treating the dry residue with any of the solvents for iodine, as for instance alcohol, chloroform, or carbon di-sulphide, which at once form deeply coloured solutions. Hence the air-dried powder is really a mixture of the original substance or substances with various decomposition products, and so is unsuited for accurate analysis. On the other hand, it might be doubted in regard to the analyses made of freshly prepared and still moist iodide, whether the results apply to a substance capable of being obtained in the dry state without decomposition.

a large excess of the strongest liquid ammonia kept at or
below 0° C. by a freezing mixture, the liquid poured off from
the easily subsiding black powder, and replaced two or
three times by fresh solution of ammonia. The powder
was then at once transferred to a corked flask, and shaken
up repeatedly, first with alcohol of 95 per cent., then with
absolute alcohol, and finally with anhydrous ether, all of
these liquids being artificially cooled. Most of the last
portion of ether, which, as well as several of the preceding
washings, was perfectly colourless, having been decanted
off, the fluid black mud was turned out upon a filter,
drained in a few moments, and the remains of the ether
swept away as vapour by placing the filter and contents
under a receiver and drawing cold dry air through in a
rapid stream. This use of alcohol and ether to re-
move water from the iodide after its formation is not
to be confounded with the employment by several ex-
perimenters of alcoholic solutions of iodine or ammonia,
or both, in making the substance in the first instance.
The product thus obtained was explosive in the
highest degree, yielding to very slight friction upon paper,
frequently producing a crackling sound from little partial
explosions when it was gently rubbed under water, and
in two instances exploding in some quantity under water,
with much violence and complete shattering of the

vessel.

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Equiv. to I 2771

No. 3.

O'172 grms. 0'142 27

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6.889
39723 12

Nos. 1 and 2 refer to the same lot of material (separately
decomposed, however); No. 3 to the product from a
repetition of the same process.
These numbers correspond to-
No. I.
No. 2.

N (assumed) 14'0
373'02

Millon and Bineau, it is true, seem to have aimed at guarding against this difficulty by drying the materials, side by side with solid potash, under a jar of gaseous ammonia. Bineau remarks that some of the gas is at first absorbed by the water moistening the powder, but that as the drying proceeds the gas recovers (" à peu près ") its original volume, and that so moisture is gotten rid of without the iodide being decomposed. But, without qualitative examination of the gas, or a very accurate determination of its volume, this does not afford satis- or, for I atom of nitrogenfactory proof that the dry substance is unchanged. I have observed continuous, though slow, evolution of little bubbles of nitrogen from the freshly prepared powder when kept under strong aqueous ammonia, though in this case no free iodine can be found, since as fast as it is liberated

it reacts with the excess of ammonia, reproducing the nitrogen iodide, and forming more ammonium iodide, which latter therefore tends to accumulate in the liquid, and is thus to be found in the residue from drying up a moist mass of the powder in an atmosphere of ammonia.

I have applied a different method, which is often useful under other circumstances, for quickly getting rid of water, namely repeated and rapid washing with absolute alcohol, followed by ether, and final evaporation of the lastnamed volatile liquid.

20 or 30 grms. of iodine was dissolved in a minimum of 95 per cent. alcohol, and precipitated by pouring into a large volume of cold water. The finely divided iodine was washed several times by decantation, then gently triturated for several minutes in a porcelain mortar with

* Ann. Ch. Phys. [2], 42; 200 (1829).

+ Ann. Ch. Phys. [2], 69; 78 (1835).

Ann. Ch. Phys. [2], 70; 270 (1838); and [3], 15; 71 (1845).

$ Chem. Soc. Q. Journ., 4; 34 (1851).

Ann. Ch. Pharm., 84; 1 (1852).

Pogg. Ann., 119; 421 (1863).

I

....

14'0

378.74

No. 3. Calc. for NIg. 14'0 14'0

367'04

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381.0

No. 3. 2.89

Atoms of iodine B-Another specimen, similarly prepared, but with weaker ammonia, without any precaution as to cooling the materials used, and in a room the temperature of which was about 23° C., gave

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Of the above resultsA distinctly represents the atomic ratio N: I=1: 3, fully confirming Stahlschmidt's conclusion that the tri-iodide can be obtained quite free from hydrogen. B corresponds well with N : Î= 2: 5, and

C with the proportion found as the result of several earlier experiments, N: I=1: 2.

If B be admitted to stand for a definite compound, and not a mere mixture of A and C, which is rendered probable by the fairly close agreement of the results obtained with the calculated figures, there must be two atoms of nitrogen in the molecule, and the formula will be N2HI5. This formula may almost as well be deduced from Bunsen's anaylsis of one of the products he obtained (by addition of ammonia to a solution of iodine in nitro-hydrochloric acid, diluted with water, and rapidly washing with cold water) as that which he has himself assigned, viz., NH3.4NI3, since the figures stand—

Calc. for N2HI,. Calc. for NH.4NI3.

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Found by Bunsen. 0'008143 or assumed 4:38 O'174417

CHEMICAL NEWS, June 13, 1879.

Experiments of Bunsen (first product, using anhydrous alcoholic solutions of ammonia and iodine). He himself assigned the formula NH3.NI3.

H

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H

I

It is much more doubtful whether we should add

Experiments of Milon (in 1838). The product dried under a receiver filled with gaseous ammonia had lost its extreme explosiveness, and no doubt contained ammonium iodide.

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93.82* I HAVE lately had an opportunity of making some experiments on the softening of so-called magnesia-hard water by Clark's process. Although from a theoretical point of view there is no reason why such water should not be softed as easily as ordinary (lime-) hard water, it was thought convenient to try the experiment on a somewhat large scale, especially as I have not been able to find that any experiments on the softening of magnesia-hard water have been published before in detail.

It will be seen that the figures of the formula now proposed differ less from those of Bunsen's formula than the latter do from the results of experiment.

In view of the general fact that the compounds of nitrogen in which this element behaves as a pentad are those in which instability is chiefly observable, and noticing the various proportions in which the iodine and hydrogen have been found together united with it, it seems fairly probable that the molecule of each of these explosive compounds contains two pentad nitrogen atoms; and reviewing all that has been published on the subject, with attention to the sources of error connected with the various methods used, we seem to have established the following series of substituted products, beginning with the tri-iodide ::

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The water in question is pumped from a colliery at Collins Green, near St. Helens. The bottom of the well pleteness sake the different strata, as well as the quantity is about 96 yards from the ground, and I give for comof lime and magnesia per hundred, which hydrochloric dried at 240° F. acid dissolved out of them, the samples being previously

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This water is organically very pure and contains only small quantities of chlorides and sulphates. The hardness is almost entirely temporary, though in estimating the permanent hardness it is sometimes difficult to remove the lime and magnesia by boiling. I may as well point out in this place a common fallacy, which is that hard water by being boiled before being used for domestic purposes becomes soft. As it is generally only heated to boiling just before being used for washing or cooking it makes not much difference in the hardness of the water. The following is taken from the Sixth Report of the Commissioners appointed in 1868 to inquire into the best

CHEMICAL NEWS, Analysis of the Water of St. Dunstan's Well, Melrose.

June 13, 1879.

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I boiled Collins Green water that tested 27.8° total hardness in an ordinary tea-kettle for five minutes, and even that exceptionally temporary-hard water tested then still 17.6° total hardness. The experiments for softening this water by Clark's process were made in two series; in the first milk of lime was used, and in the second limewater. The milk of lime was prepared by mixing 5 lbs. of slaked lime of 70 per cent CaO with 6 gallons of Collins Green water. In performing the softening of the water the milk of lime was gradually added to the water during the operation, the mixture being well agitated during the whole experiment.

In three experiments the hardness was reduced from 23.3° which the water tested originally to 50°, 5'5°, and 5'7. The total solids were reduced respectively from 33'9 to 130, 33'6 to 12.2, and 33.6 to 13.6 grs. per gallon. The softened water, after it had been standing in stoppered bottles for a few days, formed a little deposit, and its hardness was then 3'5° in all cases. The analysis showed that then the lime had been reduced from 9'13 to 1.62; the magnesia from 5:23 to 0.23 grs. per gallon.

There were used on an average 1465 gallons of water to 3.5 lbs. of CaO, corresponding to 2.67 lbs. of lime of 90 per cent per 1000 gallons. Theoretically to precipitate the lime and magnesia as far as I have done in my experiments would require 2.31 lbs. of CaO per 1000 gallons.

The experiments for softening with lime-water were carried out in a similar way. A measured quantity of the lime-water was put into the mixing tank, and the Collins Green water run into it until nearly all the lime of the former was taken up, which in these experiments as well as in those with milk of lime was ascertained by the well known silver test. The mixture was well agitated during the whole experiment. A great advantage in working with lime-water is that it requires less agitating than working with milk of lime.

In four experiments the hardness was reduced from 23'3°, which the water tested originally, to 3'5°, 3'3°, 35°, and 3'5°. The total solids were reduced respectively from 343 to 12'0, 34'4 to 112, 34'6 to 12'0, and 34'7 to II.2. The lime had been reduced from 9'07 to 167, and the magnesia from 5'24 to 0·18 grs. per gallon.

There were used on an average 1670 gallons of water on 530 gallons of lime-water, which latter having been exposed to the air for some time before being used tested only 60 grs. CaO per gallon. This corresponds to one volume of lime-water of 60 grs. CaO per gallon to 3.15 volumes of Collins Green water, or corrected to go grs. of CaO per gallon, which strong lime-water should contain, the proportion of lime-water to Collins Green water would be 1 to 4'72. This result is not quite correct, as the lime-water had undergone a further susceptible decomposition while lying in the mixing-tank; so that at the time of its action on the Collins Green water it contained less than 60 grs. CaO per gallon. Both in working with milk of lime and lime-water the softened water settled perfectly clear after three to five hours, taken from the time that the agitation was suspended.

From these experiments it follows that magnesia-hard

259

water softens as well and as easily by Clark's process as ordinary (lime-) hard water.

I wish to point out here that in my opinion, with our present knowledge of the behaviour of magnesia-hard water towards soap solution, the hardness test in cases of water of that description cannot be relied on in any way. Mr. Wanklyn, in his book "On Water Analysis," says that magnesia takes up as much soap as 1 equivalents of lime would take up. If that were so the Collins Green water should have tested 35′9° total hardness, instead of 23.3°, which it gave on the most careful testing. It will be noticed that this is even less than the water would require if it contained an equivalent of lime for the magnesia present; for the calculated hardness would then be 29'4°. It appears to me that in the case of magnesiahard water a determination of the lime and magnesia is the only means of showing the quality of the water. Un the other hand, I quite agree with Mr. Wanklyn in putting little reliance on the distinction between temporary and permanent hardness, unless the estimations have been performed very carefully; and there are cases in which, even with the most careful working, figures for temporary and permanent hardness may be got which are not trustworthy.

ANALYSIS OF THE

WATER OF ST. DUNSTAN'S WELL, MELROSE. By WILLIAM JOHNSTONE, F.C.S., F.I.C.

An exhaustive analysis of this strongly ferruginous saline carbonated water has not, so far as I have been able to learn, been published before, although a general analysis of it was made by Mr. J. Dewar in 1870, and published in the CHEMICAL NEWS, vol. xxiv., p. 171. There has been a partial analysis of this water also by Dr. Stevenson Macadam, of Edinburgh, but as his results are very doubtful I refrain from quoting it at all. As this water is peculiar for the large quantity of iron it contains, and as its composition seems to have varied considerably since it was examined by Prof. Dewar, it is thought that another and more complete analysis will not be out of place.

Melrose is a village of some 2000 inhabitants, and is situated at the base of the Eildon Hills, in the valley of the Tweed; one of those lovely spots that are said to be particularly favourable to the curative effects of medicinal waters. The surrounding country consists principally of richly variegated fields, and the entire district teems with objects of natural beauty, while every spot on which the eye rests is associated with some incident of historic or classic interest-the ecclesiasticism and chivalry of the past, and the interest conferred by Scott in the present. The salubrity of the district is well known, and the romantic scenery, which is equalled by few places in the kingdom, presents a picture dear to the lover of nature as well as to the invalid.

The spring, which belongs to Mr. John Turnbull, of St. Dunstan's Cottage, Melrose, was accidentally discovered in 1870, when sinking a shaft for ordinary spring water. The water is said to be uniform in quantity, its temperature varies only within very narrow limits, and is quite cold. As it occurs in the spring it is perfectly clear, of a yellowish colour, but, after exposure to the air, deposits the iron as a ferric mangano-manganic oxide; it has a strong powdery odour and a decided inky taste. When taken from the well there is a disengagement of small pearly bubbles, and on being shaken up in a closed bottle liberates a large quantity of gas. The temperature of the spring on October 5, 1878, was 50° F., the temperature of the air at the same time being 62° F. The specific gravity of the water is 10019356. A careful qualitative analysis indicated the presence of the following constituents in estimable quantities :—

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In addition to the above were found traces of fluorine, butyric and phosphoric acids, along with other volatile and non-volatile organic matter.

The residue of 30 gallons was examined by means of the spectroscope for cæsium, rubidium, and thallium, but the search proved unsuccessful. The method of quantitative analysis employed was essentially that described by Fresenius under the head of " Analysis of Mineral Waters" in the last edition of his "Manual of Quantitative Analysis."

The following figures represent grammes per litre, and are the average of three determinations of each of the principal constituents, done in order to guard against error and to ensure accuracy; the amount of water taken for the several determinations was, whenever practicable, ascertained by weight.

Chlorine ..

Results of Analysis.

Barium sulphate
Strontium sulphate
Calcium sulphate ..

Magnesium sulphate
Magnesium bromide

Magnesium iodide..
Potassium chloride
Lithium chloride
Ammonium chloride
Sodium chloride
Magnesium chloride
Aluminium phosphate
Calcium phosphate
Calcium carbonate
Magnesium carbonate
Ferrous carbonate..
Manganous carbonate
Silicic acid
Crenic acid

Apocrenic acid

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..

Total ingredients calculated

I'420519

but at the same time I may mention that a considerable sum of money has been expended in the view of preventing any more surface-water entering the well, so hope at some future date to be able to favour you with another analysis.

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Bromine

0'378243 0'000305

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0'000282

0'006258 0'343063 0'018652

1*390000

Total fixed constituents. Following the arrangement adopted by Fresenius on the assumption that the strongest acids are united with the strongest bases, &c., and allowing for the fact that the more or less degree of the solubility of the salts decidedly influence the manifestation of the affinities, and in order to simplify reference and comparison, and by way of contrast, I append the results calculated as grammes per litre. (See next column.)

Gases dissolved in the water and expelled by ebullition in vacuo measured at 59° F. and 760 m.m. barometer.

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PROCEEDINGS OF SOCIETIES.

CHEMICAL SOCIETY. Thursday, June 5, 1879.

Mr. WARREN DE LA RUE, President, in the Chair. AFTER the transaction of the usual business the following certificates were read for the first time:-E. Buckney, R. E. Holloway, T. Blackburn, E. F. Mondy, E. Francis. It was announced that a ballot for the election of Fellows would take place at the next meeting of the Society (June 19).

The following papers were read :

"A Contribution to the Theory of Fractional Distilla tion," by T. E. THORPE. Wanklyn some years ago found that when two liquids of different boiling-points were mixed together in equal quantities by weight and distilled, the proportion of each constituent in the distillate was the product of its vapour-density and vapour-tension at the temperature of ebullition of the fraction. Hence, under certain circumstances the less volatile of the two substances may pass over most rapidly, whilst if the vapourtensions and vapour-densities of the two liquids are inversely proportional the mixture will distil unchanged. Berthelot observed that a mixture of 909 parts of carbon disulphide with 9.1 parts of ethyl alcohol boiled and distilled as a homogeneous liquid. An instance of this pheequal volumes of carbon tetrachloride boiling at 76.6°, and nomenon has been noticed by the author. A mixture of of methyl alcohol boiling at 65.2°, was distilled. It was found that 46'5 per cent of the whole boiled constantly between 55.6° and 55'9°, 10° lower than the boiling-point of the most volatile constituent. This mixture contained 78.1 per cent carbon tetrachloride and 21.9 per cent methyl alcohol. This proportion, 3'6 to 1, is almost identical with that obtained by multiplying the vapour-tensions of the two liquids at the temperature of the boiling-point of the mixture (55'7°) by their respective vapour densities, 487 4×15'97: 372 4×76 69:: 1:367. The distillation of the residue in the flask was continued by Mr. C. C. Starling: at first principally carbon tetrachloride, finally pure methyl alcohol passed over. The author suggests as a striking lecture experiment the following:-Three baro

some

meter tubes are filled with mercury. Into one methyl alcohol is passed; into the second some carbon tetrachloride; into the third a mixture containing by volume 3 parts of methyl alcohol to 5 of carbon tetrachloride: the depressions of the mercury column are 80, 70, and 130 m.m. respectively. The author promises a further research on the physical peculiarities of this mixture.

"Preliminary Note on the Action of Organo-zinc Compounds on Quinons," by F. R. JAPP. When finely-powdered phenanthren quinon is gradually added to zinc ethyl, diluted with ether so as not to be spontaneously inflammable, a reaction takes place with evolution of gas. The orange colour of the quinon disappears: a whitish powder is formed, which sinks to the bottom of the liquid. On decomposing this product with an excess of alcohol, boiling, and filtering hot, transparent, faintly yellowish, rectangular plates were obtained, fusing at 77°, and having the formula C18H2003. This formula can be resolved into

C16H14O2.C2H6O.

The compound C16H1402 has not yet been obtained pure; but the monacetyl derivative, C16H13O2(C2H3O), has been prepared and analysed; it fuses at 103°. The author refrains at present from discussing the constitution of the compound C16H1402, but suggests that these reactions may serve to distinguish quinons from double ketons. He intends, also, to study the action of organo-zinc compounds on other quinons and allied substances as dibenzoyl.

After some remarks by Dr. ARMSTRONG on the interest and probable bearing of the above reaction,

racter is that of a sigmoid. For a certain time there is no perceptible action; this time is the longer the lower the temperature. Reduction then commences languidly, quickly accelerating until a maximum of activity is reached, after which it diminishes until almost perfect deoxidation is effected. The maximum rate of action with hydrogen lies about 10 per cent (out of 1974 per cent) of oxygen originally contained in the copper oxide, and about 7 to 8 per cent in the case of carbonic oxide. This apparently indicates that hydrogen passes through the outer and partially reduced surface of particles to their interior more readily than carbonic oxide. The following numbers illustrate the maximum rates of reduction attained, the

gaseous currents being competent to remove o'7791 per cent of oxygen (out of 1974) per minute :

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The higher the temperature the nearer does each curve approximate towards a limiting straight line, which would be attained did deoxidation commence immediately and go on at such a rate that all the hydrogen was converted into water, and the carbonic oxide into carbonic acid. The

Dr. WRIGHT read a paper entitled "Third Report to the highest rates of reduction attained corresponded to a conChemical Society on Researches on some points in Chemical Dynamics (On the Curved Surfaces expressing the Relations between Time, Temperature, and Amount of Deoxidation of Copper Oxide by Hydrogen and Carbon Oxide)," by C. R. A. WRIGHT, A. P. LUFF, and E. H. RENNIE. This is a continuation of the previous reports by the authors on the subject. In the present paper a large number of observations have been made by reducing a uniform weight (1.15 grms.) of copper oxide (prepared by igniting pure copper nitrate) in narrow glass U-tubes heated to known and constant temperatures in vapourbaths in some cases water and paraffin baths were employed fitted with Page's gas-regulator. Equable streams of hydrogen and carbonic oxide were obtained by bubbling the gas through a wash-bottle, the stream being adjusted by a screw-clamp, and counting the bubbles. The average rate was 125 c.c. per minute. By plotting out the results thus obtained in space with reference to three planes mutually at right angles, so that the distance from each plane represents, respectively, the time of exposure, the temperature, and the percentage loss of oxygen. Points are marked on curved surfaces, the sections of which, parallel to the three primary planes, represent respectively, the amounts of oxidation produced in given times at a constant temperature, the times required to produce given

amounts of deoxidation at constant temperatures, and the amounts of deoxidation produced at given temperatures in a constant period of time. The paper was illustrated by tables, diagrams, and models of the curves thus produced, the mode of experimentation adopted being to determine for a constant temperature the amounts of deoxidation produced in varying times. At and above 160° in the case of hydrogen, and 130° in the case of carbonic oxide, the curious result was arrived at that the same mean curve is obtained whether the exposure be made all at once to a temperature for a time, T, or in periods of time t1, t2, t3, &c., which are together equal to T, provided that the interval between the periods is not too long (ten minutes). Below the above temperatures the deoxidation in an hour is greater than that produced in two consecutive heatings of half an hour each with an interval between. The curves obtained with hydrogen and carbonic oxide resemble each other in certain respects; their general cha

version of about nine-tenths of the H into H2O, &c., of CO into CO2. From the curves it is evident that, cæteris paribus, to perform a given amount of deoxidation with hydrogen requires either a higher temperature or a longer time than with carbonic oxide. The existence of "a period the acceleration in the rate of action to a maximum, &c., of incubation" during which no action takes place, and shows that what has been termed "Chemical Induction " by Bunsen and Roscoe takes place in these cases to a large experiments now in progress this does not appear to be the extent, dependent in amount on the temperature. From case when copper is oxidised by hot air. A number of observations were made on the effect of varying the speed oxide used, with the general result that a more rapid of the current of reducing gas and the weight of copper stream or a smaller weight of copper oxide corresponds to an increased percentage of deoxidation, and vice versa. Heating the copper oxide just before use causes great irregularities in the action. A large number of observations were made by enclosing the copper oxide in sealed tubes filled with the respective gases, heating for different periods, and determining whether reduction had taken The times are perceptibly longer than those found in the place or not; thus the following numbers were obtained. corresponding U-tube experiments; in every case the time at any given temperature is less with CO than with H.

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