March 30, 1893] 



NATURE 



523 



chlorides, or esters of the organic acids, primary acid hydrazines 

 are produced, of the general structure R.CO.NH.NH.,, where 

 R represents the hydrocarbon radical contained in the acid 

 Ammonia, hydrochloric acid, or alcohol is simultaneously 

 formed, according as an amide, a chloride, or an ester is 

 employed. The reactions proceed with facility and regularity, 

 frequently in the cold, and afford theoretical yields of the sub- ' 

 stituted hydrazines. For many reasons, however, the esters are 

 most convenient for the preparation of these acid hydrazines 

 upon a large scale. 



The primary acid hydrazines are colourless, non- volatile solids ' 

 which usually crystallise well. The first member of the series, 

 formyl hydrazine, H.CO.NH.NHo, melts at 54°. They are 

 usually soluble in water and alcohol, but insoluble in ether. 

 Most of them form stable salts with one molecule of hydro- 

 chloric acid. The hydrogen of the imido group NH is replace- 

 able by metallic sodium or by the radical acetyl. They possess 

 reducing properties similar to those of phenyl-hydrazine, and 

 they condense readily with aldehydes and ketones to form 

 insoluble tertiary hydrazines. Upon heating, frequently by 

 simply boiling their aqueous solutions, ihey become converted 

 into secondary symmetrical hydrazines in accordance with the 

 equation: 2R.CO.NH.NH2=R.CO.NH.NH.CO.R + N2H4. 

 The liberated hydrazine decomposes into ammonia and free 

 nitrogen. 



The secondary symmetrical acid hydrazines are very stable j 

 substances, soluble only to a slight extent in water. They are 

 usually colourless, possess high melting points, and behave as 

 acids, liy the action of powerful oxidising agents they are 

 converted into substances endowed with brilliant colours, 

 ranging from yellow to bright red, which appear to be of the 

 nature of " azo " compounds. 



Of particular interest is the substituted hydrazine obtained by 

 the aclion of hydrazine hydrate upon urea, the amide of carbonic 

 acid. When urea is boiled with hydrazine hydrate a mono- 

 hydrazide is first produced, NHo.CO.NH.NR,. This sub- 

 stance, however, is unstable and passes spontaneously into the 

 secondary symmetrical compound NH„.CO.NH.NH.CO.NH., 

 with elimination of hydrazine, N0H4. This secondary hydrazide 

 is identical with a compound of the same constitution previously 

 obtained in an entirely different manner by Thiele. 



An extremely interesting reaction occurs when the acidyl 

 hydrazines of monobasic acids are treated with nitrous acid. 

 They are directly converted into esters of azoimide, N3H, in 

 accordance with the following equation : — 



R.CO.NH.NH2-!-NO.OH = R.CO.N3-f-2H20. 



During the course of work upon this latter reaction it was 

 observed that the organic azoimides, both those containing acid 

 and those containing hydrocarbon radicles, R.CO.N3 and RN3, 

 behave in a peculiar manner with water. Thusdiazobenzene-imide 

 C,;H5.N3 resinises with a copious evolution of gas ; similarly 

 benzoylazoimide, CgH5.CO.N3, when boiled for some time in 

 contact with water evolves large quantities of nitrogen and 

 carbon dioxide, and becomes converted into a magnificently 

 crystallising base of the composition of a symmetrical diamido- 

 benzophenone, C6H4.NH2.CO.NH.^.C«H4. 



The hydrazines of dibasic acids do not yield derivatives of 

 azoimide, but break up with a violent evolution of nitrogen and 

 formation of secondary symmetrical hydrazines. For instance 

 the hydrazine of oxalic acid yields the symmetrical compound 



CO.NH.NH.CO 

 I I 



CO.NH.NH.CO 



Several of the hydrazines of unsaturated acids behave in a 

 manner peculiar to themselves. Thus the hydrazine derived 

 from fumaric acid, CjHaCCO.NH.NHs),., yields with nitrous 

 acid an extremely explosive colourless compound, of the nature 

 of a diazofumaramide, C.,Hj(CO.NH.N„.OH)2. 



Prof. Curtius has succeeded in preparing a large number of 

 double salts of metallic sulphates and chlorides with hydrazine 

 sulphate and chloride. The double sulphates are constituted 

 according to the general formula (N2H4)oH.,S04.R"S04, and 

 are distinguished by their difficult solubility and by the absence 

 of water of crystallisation. Salts of the series have been pre- 

 pared containing as the metal R" copper, nickel, cobalt, iron. 



manganese, zinc, and cadmium ; magnesium does not appear 

 capable of forming a double sulphate. The blue copper 

 salt is only soluble to the extent of one part in 1150 parts 

 of water at 10°. It dissolves in ammonia with evolution of 

 nitrogen. 



The double chlorides are constituted according to the general 

 formula N2H4.HCI.RCI. They are readily soluble in water, and 

 certain of ihem may also be recrystallised from alcohol. Some 

 contain water of crystallisation, while others are anhydrous and 

 exhibit sharp melting points. 



Hydrazine likewise forms a double phosphate with mag- 

 nesium, which closely resembles ammonium magnesium phos- 

 phate. 



Hydrazine appears to be remarkably stable towards nitric 

 acid, but Prof. Curtius has eventually obtained the nitrate, 

 N0H4.HNO3, in splendid crystals which melt at 70°. If these 

 crystals are heated suddenly they explode with great violence. 

 The acid salt, N2H4.2HNO3, loses nitric acid when its solution 

 is evaporated. It may be remembered that Prof. Curtius 

 observed a similar greater stability of the monacid salt in the 

 case of the chlorides, for upon heating the dihydrochloride, 

 N2H4.2HCI, to 140^ it was found to be completely converted 

 into the monobydrochloride, N2H4.HCI. 



A. E. TUTTON. 



THE INTERNATIONAL CONGRESS OF 

 PREHISTORIC ARCHEOLOGY AND 

 ANTHROPOLOGY. 



TT is probably unique in the history of congresses that a report 

 ■'■ of the proceedings should be published within a period of 

 three months from the time of the meeting. Such a feat was 

 accomplished by the publication committee of the International 

 Congress of Prehistoric Archaeology and Anthropology, the 

 eleventh session of which was held some time ago at Moscow. 

 All the communications are printed in French. The first volume 

 of the Report is divided into five sections ; of these the first is 

 devoted to geology and palaeontology in their relations to primi- 

 tive man. In his paper upon the constitution of the quaternary 

 deposits in Russia and their relations to the finds resulting from 

 the activity of prehistoric man, S. Nikitine draws the following 

 conclusions : — The subdivision of the stone age into palaeolithic 

 and neolithic epochs should be retained for Russia in Europe, 

 because it coincides with the geological subdivisions pleistocene 

 and recent, which in their turn are based upon palaeontological 

 facts. The study of the glacial deposits of Finland and of the 

 western region do not furnish any proof of the existence of two 

 special glacial epochs and of an interglacial epoch ; all the facts 

 can be explained by phenomena of the oscillation of a glacier 

 at the time of its gradual but irregular retreat. The 

 time corresponding to the inter-glacial epoch and that 

 of the second glaciation of the Swedes was probably 

 for the greater part of Russia the period of the formation 

 of ancient lacustrine deposits, of the loess and of the 

 upper fluviatile terraces, containing the bones of the mammoth 

 and other extinct mammals. Man lived simultaneously with the 

 mammoth during the second half of the glacial epoch 

 along the limit of glaciation, knowing amongst other 

 things the use of fire, but only making splintered flint 

 implements. As the glacier retreated man advanced to- 

 wards the north and north-west ; he arrived in Finland 

 and in the Baltic region after the close of the glaciation, and 

 after the disappearance of the mammoth ; but man then pos- 

 sessed the more advanced culture of the neolithic period, and 

 besides chipped flint implements he knew how to make imple- 

 ments of polished stone, pottery, &c. Russia in Europe does 

 not present any traces of man in the first half of the pleistocene 

 or of still more ancient man.— Prof. W. W. Dokoutchaiev con 

 tributes a valuable essay on the Russian steppes, past and 

 present, in which he deals with the last page of Russian geo- 

 logy, and comes to the conclusion that before the glacial period 

 the difference between the relative altitudes of the north-west 

 and of the centre of Russia were much more considerable than 

 at present. The author describes the carving of the 

 steppes and their surface drainage ; their soil, and that of 

 the forests; the vegetation, fauna, and climate of the 



NO. 1222, VOL. 47] 



