October 8, 1891] 



NATURE 



551 



(N2H4)2 . H2SO4. Hydrazine is found to form two sulphates 

 — an acid one, ^'2^4 . H2SO4, and the neutral one now de- 

 scribed. The acid sulphate is a beautifully crystalline salt — an 

 account of which was given in Nature, vol. xliii. p. 205. It 

 is distinguished by its high melting-point, 254° C, and its diffi- 

 cult solubility. The neutral sulphate now descri'^ed is obtained 

 by evaporation of the solution formed by neutralizing hydrazine 

 hydrate with dilute sulphuric acid, first, over a water-bath, and 

 finally, as the new salt is very deliquescent, in vacuo. It crys- 

 tallizes in large brilliant tables, melting at 85°. It is precipitated 

 in a most curious manner from its aqueous solution by alcohol, 

 separating as an oil, which, on b:ing stirred with a glass rod, 

 and in contact with a small crystal of the salt, immediately 

 solidifies to a fine mass of crystals, which, like those obtained 

 by evaporation, consist of anhydrous (N2H4)2 . H2SO4. 



The second and much longer communication describes an 

 important series of new compounds, the ketazines, obtained by 

 the action of hydrazine hydrate upon ketjne?. The simplest of 

 these new substances, the one obtained by the action of hydra- 

 zine hydrate upon acetone, is represented by the formula 



CH3S yCHs 



>C=rN— N=C< . When hydrazine hydrate is dropped 



CH3/ \CH3 



upon acetone, a most violent reaction occurs, resulting in an 

 explosion unless the acetone is surrounded by a freezing mixture. 

 When thus moderated, however, the substance above formulated 

 is produced together with water, the reaction occurring according 

 to the following equation : — 



CH 



^ 



CH3'' 



CO-}-N2H4.H20 = 



CH 

 CH, 



'\r- 



C— N— Nr=C 



/-CH3 

 -CH3 



+ 3H2O. 



By allowing the product to remain for some hoars in contact 

 with caustic potash the water is removed, and upon distillation 

 the new ketazine passes over in the pure state. It is a clear 

 liquid possessing a sharp odour somewhat resembling that of the 

 alkaloid coniine. It boils without decomposition at 131°. By 

 employing other ketones, such as methyl ethyl ketone, diethyl 

 ketone, and others of the same type, a large number of these 

 ketazines have been prepared. Those containing fatty radicles 

 are liquids, and those containing aromatic groups are solids. 

 The lowest members only dissolve in water, the solubility 

 rapidly diminishing with increase of carbon atoms. Acids de- 

 compose them in the cold, with assimilation of water, into their 

 constituents ; towards alkalie?, however, they are comparatively 

 stable. Light exerts a decomposing action upon them, speci- 

 mens placed in bright sunshine rapidly becoming yellow. Re- 

 ducing agents, such as sodium amalgam, are without action 

 upon them, and they appear further to be incapable of reducing 

 either Fehling's solution or (except after long boiling) ammonia- 

 cal solutions of silver salts. 



The additions to the Zoological Society's Gardens during the 



past fortnight include two Cormorants {^Phalacrocorax, 



sp. inc.) from New Zealand, presented by the Earl of Onslow, 

 G.C.M.G. ; a Velvet Monkey {Cercopilfiecus lalandii 9) from 

 South Africa, a White-fronted Lemur {Lemur albifrons ? ) from 

 Madagascar, presented by Captain R. C. Stevenson ; a Golden 

 Agouti {Dasyfrocta agouti), a Garden's Night Heron [Nycticorax 

 gardeni), a Heron {ArJea, sp. inc.) from Surinam, pre- 

 sented by Mr. Frank Fisher ; a Common Paradoxure {Para- 

 doxurus typus) from India, presented by Miss Bason ; two 

 Blackcaps {Sylvia atruapilla), two Lesser Whitethroats {Sylvia 

 currttca), two Goldfinches {Carduelis elegans), a Marsh Tit 

 {Parus paluslris), British, presented by Mr. J. Youn», F.Z.S. ; 

 three Common Vipers {Vipera berus), British, presented by 

 NO. II 4 5, VOL. 44] 



Messrs. A. H. R. and F. R. Wollaston ; a Macaque Monkey 

 {Macacus cynomolgus ? ) from India, presented by Mrs. 

 Gwynne ; an Indian Civet {Vivetricula tnalaccenus) hom India, 

 presented by Mr. Herbert Courtney Hodson ; two Chilian Sea 

 Eagles {Gerafioaitus melanoleucus) from Chili, presented by Mr. 

 H. Berkeley James, F.Z.S. ; two Grey-breasted Parrakeets 

 {Bolborhynchiis monachits) from Monte Video, presented by 

 Mr. J. C. Wallace; two Nightingales {Daulias iuscinux), two 

 Common Whitethroats {Sylvia cinerea), a Blackcap {Sylvia atri- 

 capilla), British, presented by Mr. J. Young, F.Z.S. ; four 

 Yellow Wagtails {Moiacilla raii), British, presented by Mr. W. 

 Swaysland ; a Common Cormorant {Phalacrocorax carbo) from 

 Scotland, presented by Mr. F. T. Barry, M. P. ; fifteen Striped 

 Snakes ( Tropidonotus sirtalis) from North America, presented 

 by Mr. J. Gray ; a Solitary Thrush {Monticola cyanus), Euro- 

 pean, a Macaque Monkey {Macacus cynomolgus) from India, 

 deposited ; a Sharpe's Wood Owl {Syrnium nuchale) from 

 West Africa, a Testaceous Snake {Ptyas teslacea) from Cali- 

 fornia, two Quebec Marmots {Arctomys monax) from North 

 America, two Scaly Doves {Scardafella squamosa) from South 

 America, purchased ; a Ruddy-headed Goose {Bernicla rubiJi- 

 ceps) from Falkland, received in exchange. 



OUR ASTRONOMICAL COLUMN. 



Physical Appearance of Periodic Comets. — Comets 

 possess no personal characteristic appearance ; but Mr. Barnard, 

 writing to the Astronomical Journal, No. 246, suggests that it 

 may be possible to arrange those of short period according to 

 their physical peculiarities. To the first class he would assign 

 those comets which are large, round, and very gradually brighter 

 in the middle, with no special condensation, and of a very 

 diffused nature. They have no nucleus or tail, and are so de- 

 cidedly periodic that, trusting to this peculiarity, Mr. Barnard 

 predicted that the comet discovered by Swift in November 1889, 

 and D' Arrest's comet at its return last year, were of short period. 

 The most distinctive members of this class of csmets are 

 D' Arrest's, Swift's 1880, Brooks's 1886, and Swift's 1889. 

 There are few nebulse that resemble this class. A much larger 

 and less exclusive class contain comets which are comparatively 

 small, and which have an indefinite central brightness or nucleus. 

 Many of the parabolic comets resemble these, and there are 

 hundreds of nebulae exactly like them in telescopic appearance. 

 To this class are assigned comets Faye ; Wolf, 1884. III. ; 

 Finlay, 1886 VII. ; Brooks, 1889 V. ; Spitaler, 1890. It is 

 possible that the peculiarities of these two distinct classes of 

 short-period comets may furnish some information as to their 

 relative ages. 



Discovery of Tempel-Swift's Comet.— Mr. Barnard 

 found this cooiet on September 28, and Mr. W. F. Denning 

 discovered it independently two days later about 4° south- 

 west of its computed po5iti:)n. The comst passes perihelion 

 in November. Its position, according to M. Bossert's ephenieris, 

 is as follows : — 



Ephemeris for Paris Midnight, 

 1891. Right Ascension. DecUnatioa. Brightness, 



h. m. s. o / 



Oct. 6 ... 21 6 2 ... -H 3 248 ... 7-01 



3 540 



4 247 ... 777 



4 56-9 



5 308 ... 8-6i 



6 6-4 



6 43 '9 ... 9 '54 



7 23 "4 



8 48 ... 10-54 



8 48 3 



9 340 ... 11-64 



10 22'2 



11 12-8 ... 12-83 



The comet is therefore in Equuleui at the present time, and 

 moving towards Pegasus. 



