October 5, 1893] 



NATURE 



547 



career, by supplying useful handbooks of a clear and praclical 

 character, dealing with those subjects which are absolutely 

 essential in a business life," has received an addition by Mr. H. 

 De B. Gibbins, entitled "British Commerce and Colonies." 



A SECO.ND edition of Mr. J. R. Ainsworth Davis' "Element- 

 ary Text-book of Biology" (Messrs. Charles Griffin and Co.) 

 having been called for, the book has been thoroughly revised 

 and much enlarged, and a number of illustrations have been 

 added. Part II. (Animal Morphology and Physiology) has 

 had its value enhanced by the addition of a chapter on the 

 Distribution of Animals. 



Messrs. Whittaker's library of popular science has received 

 an addition in the form of a volume entitled " Electricity and 

 Magnetism," by Mr. S. R. Bottone. The illustrations in the 

 l)ook are a little coarse, but are just what a teacher requires to 

 elucidate the text. Mr. Bottone is evidently at home in his 

 subject, and he knows the way to present it to the general 

 reader. 



Dr. J. W. Gregory has conferred a benefit upon students i 

 of petroj^raphy by translating the " Tables for the Determination 

 of the Rock-Forming Minerals," prepared by Prof. F.Loewinson- 

 Lessing. The tables of Rossenbach and Michel Levy and 

 Lacroix leave nothing to be desired in the matter of complete- 

 ness, but they are of little use to the elementary student for 

 purposes of identification. By means of the synoptical tables, 

 however, the commoner rock-forming minerals can easily be 

 determined when their characters have been microscopically 

 observed. A very suitable introduction to the tables is a 

 description of the petrological microscope, by Prof. Grenville 

 A. J. Cole. Messrs. Macmillan are the publishers of the 

 translation. 



iThe October number of Natural Science is of unusual 

 interest. Among the articles are the following : " The Effect 

 of the Glacial Period on the Fauna and Flora of the British 

 Isles," by G. W. Bulman; "Some Recent Researches on the 

 Habits of Ants, Wasps, and Bees," by George H. Carpenter; 

 and "The Recent Plague of Wasps," by Oswald H. Latter. 

 Dr. C. Herbert Hurst theorises upon " The Digits in a Bird's 

 Wing," and Mr. J. T. Cunningham upon " The Problem of 

 Variation." In addition there are numerous notes and book- 

 notices. 



An investigation of the composition and properties of the 

 dangerously explosive iodide of nitrogen has been carried out 

 by Dr. Szuhay in the laboratory of the University of Buda- 

 Pesth, and an account of his interesting experiments is contri- 

 buted to the latest publication of the BerUhte. A large 

 number of investigators have previously attacked this somewhat 

 fascinating subject, but the knowledge hitherto accumulated has 

 been insufficient to enable us to express with certainty its com- 

 position. One of its properties, its unparalleled readiness to 

 explode with or without provocation, has been so much to the 

 fore as to almost entirely exclude investigation of its more im- 

 portant, although less sensational, chemical properties. One 

 variety of the substance, which was obtained by Dr. Szuhay by 

 adding ammonium hydrate solution to powdered iodine, was 

 found to be so pre-eminently disposed to detonative decom- 

 position that it frequently exploded even under water, and if it 

 were successfully transferred while wet to a filter it exploded 

 upon the passage of the .first draught of air. An attempt to 

 ascertain its comp isition by careful decomposition with 

 sulphurous acid resulted in the complete pulverisation of the 

 containing vessel. Iodide of nitrogen was first prepared by 

 Curtois by mixing alcoholic solutions of iodine and ammonia. 

 He considered it to be the tri-iodide NI3, an opinion which 

 was subsequently shared by Gay Lussac. MiUon and Mar- 



NO. 1249, VOL. 48] 



chand afterwards expressed the view, unsupported, however, by 

 experimental evidence, that it contained hydrogen, and might 

 be represented by the formula NH.,I. More recently Bineau, 

 and in this country Dr. Gladstone, have adduced more trust- 

 worthy evidence, from its mode of decomposition by an aqueous 

 solution of sulphuretted hydrogen and by sulphurous acid, that 

 this extraordinary substance does indeed contain hydrogen, 

 but only to the extent of one atom, its constitution being NHU. 

 Bunsen, however, subsequently communicated to the Annalen 

 the view that iodide of nitrogen consists of NI3, but that accord- 

 ing to its mode of preparation it contains more or less ammonia. 

 Finally, Stahlschmiedt has brought forward the further 

 hypothesis that when an alcoholic solution of iodine is mixed 

 with aqueous ammonia the substance NI3 is produced, but that 

 when alcoholic ammonia is employed the product possesses the 

 composition NHI... The result of all this conflicting testimony 

 has been to leave the question of the composition of iodide of 

 nitrogen an open one. 



Iodide of nitrogen was prepared by Dr. Szuhay, after investi- 

 gating most of the methods hitherto described, by adding excess of 

 aqueous ammonia to a concentrated solution of iodine in potas- 

 sium iodide. It is thus obtained in the form of a very fine pow- 

 der, which was found to be capable of safe purification by wash- 

 ing with a dilute solution of sodium sulphate. It is requisite to 

 protect the filter from draughts of air which are liable to induce 

 explosion. The purified substance, of course in a moist condi- 

 tion, as it cannot be dried without explosion, was analysed by 

 decomposition with a solution of sulphurous acid of known 

 strength and estimation of the amount of iodine and ammonia 

 in the solution. Its composition was indubitably proved to be 

 NHIo, thus confirming the earlier work of Dr. Gladstone and 

 of Bineau. This conclusion is powerfully supported by the fact 

 that Dr. Szuhay has been able to prepare a silver derivative of 

 the compound by replacing the hydrogen atom by silver. This 

 silver compound is readily obtained by adding powdered oxide 

 of silver or an ammoniacal solution of silver nitrate to iodide of 

 nitrogen suspended in water. It is a black flocculent substance 

 which is quite as explosive as iodide of nitrogen itself. When care- 

 fully dried the least rise of temperature provokes explosion. It 

 also detonates upon being struck or evenjwhen brought into gentle 

 friction with any other substance. When warmed under water, 

 or when treated with dilute acids it is quietly decomposed, silver 

 iodide being deposited, free iodine liberated, and free nitrogen 

 escaping with effervescence. The relative amounts of these pro- 

 ducts of decomposition conclusively prove the compound to 

 possess the composition Ag NIj. Moreover, considerable evi- 

 dence is also adduced to show that potassium, sodium, and 

 barium replacement compounds are capable of existence in solu- 

 tion. The existence of the compound HNIo is thus fully de- 

 monstrated, and whether or not tne compounds NIj and NH.,I 

 are likewise capable of formation under different experimental 

 conditions is a question which doubtless further work will elu- 

 cidate. It is not unworthy of notice that there is a considerable 

 amount of resemblance between this extraordinarily explosive 



.N 



substance and the similarly distinguished azoimide H - N 



/, 



N 



for both contain the imido group NH the hydrogen of which is 

 capable of being replaced by silver and other metals, and both 

 appear in consequence to be endowed with a somewhat acid 

 nature by the two atoms of negative iodine in the one case, and 

 the negative diazo-nitrogen group in the other. 



Notes from the Marine Biological Station, Plymouth. — Last 

 week's captures include the Annelids Myrianida inaciilata (one 

 of these with a chain of buds), Spluerodorum piripatiis and 

 Siplionostoma uncinatunt, the tubicolous Gephyrean Phoronis 



