44 



NATURE 



{Nov. 14, 1889 



A SECOND edition of Prof. Tait's " Light " (A. and C. Black) 

 has been issued. The author says that in revising the work he 

 has made use of various notes jotted down from time to time on 

 his own copy, mainly as the result of questions asked, or of 

 difficulties pointed out, by students who were reading the book 

 with care. Suggestions of this kind he has found to be almost 

 always of value, as they tend to make the book better suited to 

 the wants of the class of readers for whom in particular it was 

 designed. 



Persons interested in ferneries and aquaria will find much 

 to attract them in a little volume entitled "Ferneries and 

 Aquaria : a Complete Guide to their Formation, Construction, 

 and Management," by George Eggett, Sen. This is one of a 

 series of " practical guide-books " issued by Messrs. Dean and 

 Son. 



The third volume (new series) of the Reliquary (Bemrose and 

 Sons) has been issued. It opens with an interesting illustrated 

 article on two Assyro-Phoenician shields from Crete, by the Rev. 

 Joseph Hirst. Mr. John Ward contributes three illustrated 

 papers of scientific value — on Rains Cave, Longcliffe, Derby- 

 shire ; on relics of the Roman occupation. Little Chester, 

 Derby ; and on recent diggings at Harborough Rocks, 

 Derbyshire. 



Messrs. Dulau and Co. have sent us a "Catalogue of Zoo- 

 logical and Palseontological Works." It includes works on 

 Reptilia and Amphibia, and on Pisces. 



The atomic weight of palladium has been redetermined by 

 Dr. E. H. Reiser {Amer. Chem. Journ.). Among all the 

 atomic weights at present adopted by chemists, that of palladium 

 has been one of the most imperfectly determined, for the dis- 

 crepancy between the results of the various previous investiga- 

 tions is most unsatisfactory. In 1826, Berzelius obtained the 

 value 1 13 '63 from a consideration of the proportion in which 

 palladium combines with sulphur. Two years later, the 'same 

 distinguished chemist derived a much lower value from analyses 

 of potassium palladious chloride, 2KCI . PdClg ; known quan- 

 tities of this salt were heated in a current of hydrogen, and the 

 residuary potassium chloride and reduced palladium weighed. 

 Recalculated by Profs. Meyer and Seubert, utilizing all the re- 

 fined corrections of the present day, these analyses yield the 

 value 106 -2 — a number which is almost identical with the atomic 

 weight obtained by Dr. Reiser. In 1847, however, Quintus 

 Icilius also investigated the subject, and, from determinations of 

 the loss in weight which potassium palladious chloride under- 

 goes when heated in a current of hydrogen, obtained the value 

 III '88. No other determinations having since been attempted, 

 and the number 112 or 113 being certainly too high from con- 

 siderations of the position of palladium among the metals, the 

 number 106 "2 obtained from Berzelius's second analysis recalcu- 

 lated by Meyer and Seubert has been universally adopted. To 

 place the subject out of all doubt. Dr. Reiser has re-examined 

 it from a totally different standpoint. The double chlorides 

 of palladium and the alkalies, such as 2K:C1 . PdCla and 

 2NH4CI . PdClj, are found to be unsuitable for atomic weight 

 determinations ; they retain water of decrepitation with great 

 tenacity, and, after drying, are too hygroscopic for accurate 

 weighing. On the other hand, . the yellow crystalline 

 salt, palladammonium chloride, P'd(NH3)2Cl2, is a much 

 more suitable substance. It is eminently stable, can be 

 obtained in a state of practically perfect purity, contains no 

 water of crystallization, does not retain water after drying in a 

 desiccator, and the dried salt is not hygroscopic. Weighed 

 quantities of it contained in a platinum boat were introduced into 

 a combustion tube and heated in a stream of pure hydrogen. 

 The hydrogen was rapidly absorbed, changing the bright yellow 

 colour into black, metallic palladium and ammonium chloride 



being formed. The absorption of hydrogen occurred so readily 

 that it was only necessary to warm one end of the boat when the 

 heat of the reaction was found sufficient to complete the reduc- 

 tion of the whole. Pd(NH3)2Cl2 -f Hj = Pd -^ 2NH4CI. Af er 

 raising the temperature so as to volatilize the ammonium 

 chloride, the finely divided palladium adhered together in the 

 form of a porous bar having the shape of the boat. It was 

 allowed to cool before weighing until just below a red heat in the 

 current of hydrogen so as to prevent oxidation, and afterwards 

 the hydrogen was displaced by dry air to prevent its occlusion. 

 Two series of determinations were made, the salt for the second 

 series being prepared from the reduced palladium of the first. 

 The mean of eleven experiments in the first series gave the num- 

 ber 106 "352, and of eight in the second series 106 "350. The 

 maximum value obtained was 106 '459, and the minimum 

 106 •286. The mean result 106*35 practically confirms thai 

 obtained by recalculating the results of Berzelius's second 

 analyses. 



In our note in these columns three weeks ago (vol. xl. p. 655), 

 upon pinol, the new isomer of camphor, it was pointed out that the 

 nitrosochloride of pinol forms with j8-naphthylamine an interest- 

 ing base, C2i,H24N202, isomeric with quinine. This base, how- 

 ever, is not the first isomer of quinine which has been prepared, 

 for an artificially prepared base of the same empirical formula 

 was described by Dr. Rohn, of University College, Liverpool, in 

 the Journal of the Chemical Society for 1886, p. 500. 



The additions to the Zoological Society's Gardens during the 

 past week include three Rhesus Monkeys {Afacacus rhesus 

 $6 6) from India, presented respectively by Colonel Cuthbert 

 Larking, Mr. James T. Wilson, and Mrs. Charles Sainsbury ; 

 a Hairy-rumped K^ovX\{Dasypi'octa prymnolopha) from Guiana, 

 presented by Mr. Henry E. Blandford ; a Common Polecat 

 {Mustela pzitorius) from Norfolk, presented by the Earl of 

 Romney ; a Northern Mocking Bird {Mimus polyglottis) from 

 North America, presented by Miss E. Breton ; two White 

 Pelicans {Pelecanus onocrotalus), a Crested Pelican (Pelecanus 

 crispics) from Roumania, a Common Boa {Boa constrictor), 

 a Neck-marked Snake {Geoptyas coUaris) from Panama, a 

 Mocassin Snake ( Tropidonotus fasciatus) from North America, 

 deposited ; two Common Siskins {Chrysomitris spinus), two 

 Twites {Linota Jlavirostris), two Lesser Redpoles {Linota 

 rufescens), four Snow Buntings {Plectrophanes nivalis), two 

 Knots ( Tringa canutus), a Bar-tailed Godwit {Limosa lapponica), 

 British, a Rosy-billed Duck {Metopiana peposaca 6 ) from South 

 America, purchased. 



OUR ASTRONOMICAL COLUMN. 

 Objects for the Spectroscope, 

 Sidereal Time at lo p.m. at Greenwich, November 14 = ih. 

 36m. 45s. 



Remarks. 



(i) This is one of Herschel's double nebulas. Dr. Huggins 



notes that both components give a gaseous spectrum, but could 



only be certain of the presence of the chief nebula line near 500, 



although 495 was strongly suspected. He notes, also, that there 



