DR. GLADSTONE ON THE EXPLOSIVE COMPOUND VI.-Onl the Explosive Compound usually de~o~~~~~e~ loda’deof Nitrogen. BY J. H. GLADSTONE,Ph.D. F.C.S. The following experiments were made last summer vith a view to settle the real composition of the so-called iodide of nitrogen.” This substance resulting from the mutual action of iodine and ammonia in U8UA LLY DENOMINATED IODIDE OF NITROGEN. solution has already been the subject of much investigation ; and the study of its reactions by different chemists has led to four different formulze being assigned to it. The extremely explosive character of the substance precludes the idea of analysing it in the usual manner as it would be impossible to place a portion in the scale-pan of a balance with any safety after it had been dried.Indirect modes of analysis by which the relative proportion of its constituent elements is determined appear to be offered by various decompositions which the black powder may be made to undergo. "I.Bineau* alone has studied any of these hitherto and his experiments led him to assign to the so-called iodide of nitrogen the composition NHI,. The quantitative results recorded below will test the truth of this €ormula. The substance employed by me was always prepared by decom- posing an alcoholic solution of iodine by means of ammonia in excess The black powder thus formed was completely washed by suffusion with distilled water and decantation. It was found that during this reaction an amount of iodide of ammonium is formed slightly exceeding half the amount of iodine employed a mere trace of iodic acid is also produced.This fact is opposed to the formula NI assigned to the black powder by Mitscherlich ;for 4 NH3+4 I=NI+3 NH I; in which case the iodide of ammonium obtained would be quite three-fourths of the iodine originally acted upon; but it decides nothing as to whether 1 2 or 8 atoms of hydrogen in the ammonia are substituted by iodine; for 2 I + 2 NH = NH I + NH I (Millon). 4 I + 3 NH = 2 NH I + NHI (Bineau). 6 I + 4 NH = 3 NH I + NI,. The black powder suffers spontaneous decomposition in pure water. Bubbles of gas are slowly given off; iodine is set free; and the solution (which is acid to test paper) contains hydriodic and iodic acids together with ammonia.In an attempt to make use of this decomposition as a means of analysis the iodic acid was found to be to the hydriodic acid in the ratio of 1 atom to 8.44 atoms; but it is not likely that the two acids always maintain the same pro-portion The addition of ammonia to the water in which the black powder is immersed tends to prevent its spontaneous decomposition. * Ann. Ch. Phgs. [3] XV 71. 332 DR. GLADSTONE ON THE EXPLOSTVE COMPOUND Potash on the contrary accelerates it. So do acids in general. A solution of carbonate of potash has much the same action as pure water. Chlorine destroys the black powder but not instantaneously ; bromine water causes its immediate decomposition. Strong nitric acid attacks it violently.Hydrosulphuric acid causes its instant decomposition without the evolution of any gas and with the formation of ammonia and hydriodic acid alone sulphur being in the meantime deposited. This affords a ready method of determining the relative proportion of iodine and nitrogen. Accordingly some of the black powder was diffused through water and a stream of hydrosulphuric acid gas was passed through it until the solution which assumed at first a red tint became colourless and smelt strongly of the gas. It wits then gently heated and filtered; the hydriodic acid was precipitated as silver-salt excess of silver was removed by the addition of a large excess of hydrochloric acid and the resulting chloride of ammonium was estimated in the usual manner.The amount of ammonio-chloride of platinum obtained was 5.83 grs. ;that of iodide of silver 12.53 grs. which is equivalent to Nitrogen . . . . 0.366 grs. Iodine . . . . . 6.75 , If we divide these numbers by the atomic weights of the respective elements we obtain Nitrogen . . . . . 261 Iodine. . . . . . 533 or the proportion of 1 atom of nitrogen to 2.04atoms of iodine. The action of sulphurous acid appeared to offer the means of determining the relative proportion of nitrogen iodine and hydrogen also if that element really be a constituent of the black powder. The transformation of the substance into ammonia and hydriodic acid takes place instantly without the evolution of any gas unless the temperature be suffered to rise considerably when a secondary action is instituted.At the same time a quantity of sulphurous acid is converted into sulphuric acid equivalent of course to the quantity of water decomposed in order to supply the necessary hydrogen. A carefully prepared fresh solution of sulphurous acid was added gradually to some of the black powder diffused through water until the decomposition was complete. The solution thus obtained was divided into two equal portions. The one portion was evapo- USUALLY DENOMINATED IODIDE OP NITROGEN. rated down with excess of hydrochloric acid and the ammonia was converted into platinum-salt ;the other portion was very gently warmed to expel sulphurous acid nitrate of silver was added to precipitate the iodine and subsequently the sulphuric acid was thrown down as baryta-salt.There were obtained 8.65 grs. of ammonia-chloride of platinum ;18.53 grs. of iodide of silver; and 17.57 grs. of sulphate of baryta. This is equivalent to Nitrogen ......0.542grs. Iodide .......9.98 , Sulphuric acid ....6-04 , Dividing these numbers by the atomic weights we obtain Nitrogen .....388 or 1 equiv. Iodine ......788 ,,2.03 , Sulphuric acid ...1520 ,,3.92 , This confirms the preceding result and shows moreover that the black powder contains 1 equivalent of hydrogen; for 1 atom of ammonia 2 atonis of iodine and 4 atoms of sulphuric acid can only arise from 4 atoms of sulphurous acid 4 atoms of water and NHI,. NHI I-4 SO +4 HO =NH +2 HI +4SO,. Serullas* observed that when this black powder is decomposed by dilute hydrochloric acid a red solution is obtained from which the addition of an alkali reprecipitates the explosive compound a portion however being always decomposed into its elements.Millont made the further observation that if the black powder be treated with a saturated solution of hydrochloric acid it dis-appears without the evolixtion of any gas and the resulting solution is neutral to test paper. He believes that the substance is resolved into ammonia and the acids of iodine and concludes from this peculiar reaction that the explosive body must have the composition NH I. It is difficult to see how this conclusion follows from the premises the more natural idea would be that the black powder being ammonia in which a portion of the hydrogen is replaced by iodine combines as such with the hydrochloric acid thereby neutralising it.Yet Serullas has long since recorded various reasons tending to prove that this is not the case :he believed that the solution contained iodic and hydriodic acids along with the hydro- chloric acid; and what confirmed him in this belief was the obser- *Ann. Ch. Phys. XLII 200. t Ann. Ch. Phys. [2] LXIX 83. DB. GLADSTONE ON IODIDE OF NITROGEN. vation that when these two acids of iodine are mixed together and supersaturated with ammonia the explosive compound is obtained especially if hydrochloric acid be present. Now this certainly arises from the two acids when mixed reacting upon one another to produce free iodine; and the explanation of the eminent chemist just mentioned does not account for the fact that when the decom- position of the black powder has been effected by water or other acids than the hydrochloric a solution is obtained from which ammonia does not reprecipitate it.On repeating the experiment I found that the red solution obtained by dissolving the explosive compound in strong hydro- chloric acid contains not a trace of free iodine; it gives no blue colour with starch. When evaporated to dryness in a water-bath it comes out as a solid body of a somewhat yellow colour soluble in water or alcohol and neutral or nearly so to test paper. If potash or baryta-water be added to this solution it re-precipitates the black powder. The addition of nitrate of silver causes a mixed precipitate of chloride and iodide of silver.Sulphurous acid gives rise to a separation of iodine which a larger quantity converts into hydriadic acid. The dried substance when heated per se suffers decompo- sition; it gives off a pungent odour then iodine sublimes and afterwards chloride of ammonium. Ether extracts from the evapo- rated solution that which imparts to it its colour and leaves some chloride of ammonium behind. All these reactions are perfectly explained by considering the solution produced by means of hydro- chloric acid as a mixture of chloride of ammonium and protochloride of iodine. The reaction is as follows NHI,+3 HCl=NH C1+2ICI. And it has been already ascertained by Mitscherlich that the explosive compound is produced when protochloride of iodine is treated with ammonia.The reaction in this case will be 2 IC1+ 3 NH =NHI +2 KH C1. The same cheniist states that terchloride of iodine with ammonia causes the formation of the same black powder. If this be really the case we must suppose that some one of the oxygen-compounds of chlorine is formed at the same time. But an aqueous solution of terchloride of iodine is to say the least of very uncertain consti- tution; and even the liquid resulting from the action of aqua regia upon iodine may contain the protochloride. If iodic acid be dis- solved by strong hydrochloric acid in the cold a yellow solutiofi DH.. HOPMANN’S COMPOUND TESTING JET. is obtained having a chlorous odour; but I find that the addition of ammonia causes no black precipitate in such a solution unless it has been previously heated.In accordance with the practice now adopted in naming those compounds in which two equivalents of hydrogen in ammonia are replaced by two of another body this explosive compound should bear the appellation “Iodimide.” When this paper was read before the Society Dr. Playfair re-marked that some time since he had prepared the same explosive powder by pouring a solution of hypochlorite of lime into a solution of iodide of ammonium He believed they were in the proportion of single equivalents; and as this reaction may be readily explained under the supposition that the compound is NH I it had confirmed in his mind the view propounded by Millon.Upon considering the reaction subsequently I perceived that a compound having Bineau’s formula might equally be obtained from the same salts in the same proportions but that ammonia would appear among the products of decomposition. The reaction might be either CaO C10 + NH,I=NH I +2 Ca C1+4 I30 or 2(Ca0 C10)+2 NH,I=NH I,+2 Ca C1+4 HO+NH Upon repeating the experiment with bleaching powder any alkaline reaction of which had been more than neutralized by acetic acid I found a large quantity of ammonia set free. This reaction then like every other with which I am acquainted indicates the same composition for this explosive powder.