232 



NATURE 



[July 6, 1893 



lectures delivered at meetings of the Society during 1892, and 

 some notes on the local forms of Helix memoralis and horUnsis, 

 prepared by Mr. A. Belt. There are few societies in the en- 

 virons of London that are able to publish such satisfactory 

 reports of their proceedings. 



It is only in a very narrow and restricted sense that statistical 

 information gained by the ordinary census can be accepted as an 

 indication of the educational status of a country. However, an 

 attempt was made to obtain some figures under this head during 

 the census of the colony of Tasmania in 1891. The standards 

 taken was the ability to read and write, to read only, and to be 

 able to do neither. The tabulation of the results of the inquisi- 

 tion shows that the percentage of persons who said they could 

 read and write reached a maxitnim of 95'04 between the ages 

 of fifteen and twenty, and then decreased gradually to 55 68 for 

 persons of eighty-five years of age and over. Of all the persons 

 whose respective ages were not les; than fourteen, 8877 per 

 cent, could read and write, 3 '50 per cent, could read, and 773 

 per cent, avowedly lacked the qualifications for either of those 

 classes. 



Mr. S. Cotterell has compiled a little handbook to 

 various publications, documents, and charts connected with the 

 rise and development of the railway system of Great Britain and 

 Ireland. The book is published by Mr. Edward Biker, John 

 Bright Street, Birmingham. It is a compact little bibliography 

 of railway matters, and deserves to be issue.1 in a much better 

 form than it is at present. 



Two papers are contributed to the current journals upon the 

 hitherto unisolated tetrachloride of lead. The earlier of the 

 two, by Prof. Classen and Herr Zahorsky of the Aachen 

 laboratory, is communicated to the Zeitschrift ficr Anorganische 

 Chemie. During the course of an interesling series of experi- 

 ments with liquid chlorine, it was observed that the liquid was 

 entirely without action upon pure lead dichloride, PbClj, but 

 that in pre-ience of concentrated hydrochloric acid a solution of 

 tetrachloride of lead was produced. Twenty-five grams of lead 

 chloride were placed in two hundred cubic centimetres of fum- 

 ing hj'drochloric acid, and the mixture cooled by means of ice 

 and salt. Liquid chlorine was then added and the vessel 

 closed. After two days the lead dichloride had all disappeared 

 and a homogeneous yellow liquid remained, consisting of a 

 solution of lead tetrachloride in hydrochloric acid. All 

 attempts to isolate the tetrachloride were unavailing, but upon 

 adding ammonium chloride a double salt of the composition 

 2PbClj.5NHjCl crystallised out. This salt, containing 

 tetrachloride of lead, forms yellow crystals which are quite 

 permanent in closed vessels and withstand a temperature of 

 100° without change. The crystals are decomposed by water. 

 If only a small quantity of water is added the dichloride 

 separates and a solution of hypochlorous acid is formed. If 

 much water is added a clear brown solution is produced which 

 probably contains plumbic acid, Pb(OH)j ; this solution rapidly 

 decomposes with separation of lead dioxide, PbOj. 



The second paper, by Prof. Friedrich, of Graz, is contributed 

 to the Berichte. Prof. Friedrich has succeeded in isolating the 

 pure tetrachloride itself, PbClj. A solution in hydrochloric 

 acid was first obtained by the action of chlorine gas on lead 

 dichloride suspended in hydrochloric acid. From this the 

 double salt with ammonium chloride was prepared by the addi- 

 tion of sal-ammonia to the liquid product. According to Prof. 

 Friedrich, the composition of this salt is represented by the 

 formula PbClj.aNHjCI. It was obtained in well-defined 

 combinations of the octahedron and cube, and would appear to 

 be isomorphous with the corresponding tin salt, (NHjoSnCIc, 



NO. 1236. VOL. 48] 



the well-known /z«^ salt which was formerly so largely used as 

 a mordant for madder dyes. When this double salt containing 

 tetrachloride of lead is placed in strongly cooled oil of vitriol a 

 somewhat energetic reaction occurs, the chloride of ammonium 

 being decomposed with evolution of hydrochloric acid gas. 

 But, strange to say, the tetrachloride of lead is not attacked by 

 concentrated sulphuric acid, and it separates in yellow drops, 

 which finally coalesce to form a heavy yellow liquid, which sinks 

 to the bottom of the vessel. This may be purified by repeated 

 agitation with oil of vitriol, and is eventually obtained after 

 separation as a clear, yellow, very highly refractive, heavy but 

 mobile liquid, which yields numbers upon analysis agreeing with 

 the formula PbCIj, fumes in contact with moist air, and decom- 

 poses slowly with separation of lead dichloride and escape of 

 chlorine gas. Upon warming it suddenly decomposes with 

 explosion, the dichloride of lead being produced in the form of 

 a cloud tinted somewhat yellow by the free chlorine. Its 

 specific gravity at o" is 3'l8. At - 15" it solidifies to a mass ol 

 yellow crystals. With a little cold water it forms a hydrate, 

 probably Pb(0H)4, which readily decomposes, and with excess 

 of water it yields a precipitate of peroxide of lead PbOj. 

 When added to a little very cold concentrated hydrochloric 

 acid a crystalline compound, probably of the composition 

 PI0CI4.2HCI, is formed. When mixed with oil of vitriol and 

 warmed in a current of hydrochloric acid gas the liquid may be 

 partially distilled. As soon, however, as temperature reaches 

 about 105° explosion occurs, as described above. In this 

 respect, also, lead tetrachloride resembles tetrachloride of tin, 

 which may be distilled without decomposition from a mixture 

 with sulphuric acid. 



Notes from the Marine Biological Station, Plymouth. — 

 Recent captures include large swarms of Salps, the nurses and 

 young chains of Thalia democratica-mucronata. From the 15"' 

 to the 25th they were very common and in good condition ; 

 after the 25th they became reduced in number, and were much 

 injured by the storm which occurred last week. In addition to 

 the above there were observed numbers of Obeha and Thau- 

 mantias medusje ; and from time to time Echinoderm, Annelid, 

 and Miiller's larvae, as well as Cyphonautes and the Eudoxia larva 

 of Muggiira. The Mollusc Nassa incrassala is now breeding. 



The additions to the Zoological Society's Gardens during the 

 past week include a Macaque Monkey [Macacus cynomolgus, i ) 

 from India, presented by Mr. W. Henegan ; a Rhesus Monkey 

 {Macacus rhesus, 9 ) from India, presented by Mr. J. H. Brown ; 

 three Common Marmosets [Hapale jacchus) from Brazil, pre- 

 sented by Mr. Hope Gibson; a Brown "Rtm {Ursus anlos,9) 

 European, presented by Mr. F. Collier, F.Z. S. ; two Wild 

 Swine (Siis scrofa, c5 9 ) from North Africa, presented by Mr. 

 Jasper A. Mathews; a Purple Heron (A rdea purpurea) British, 

 presented by Mr. R. Heywood ; a Leadbeater's Cockatoo 

 (Cacatua leadbeateri) from Australia, presented by Mrs. Anna 

 Margaret Hills ; a Guilding's Amazon ( Chrysalis guildingi) from 

 St. Vincent, W.I., two Tree Boas {Corallus hortulanus) from 

 Grenada, W.I., presented by the Hon. Sir Walter Hely- 

 Hutchinson, K.C. M.G. ; a Brazilian (Z^x\2txa2. {Cariama cris- 

 tala), a Barn Owl (Sirix Jlammca), a King Vulture [Gypagus 



papa), a Buzzard {Buteo sp. inc.) from Brazil, presented by 



Mr. Howard C. Wolfe ; an Illiger's Macaw {Ara maracana), 

 two yellow-headed Conures (Conurus Jeiidaya) from Brazil, two 

 Rufescent Teguexins ( Tupinambis rufescens) from Mendoza, 

 deposited ; six European Beavers (Castor — — ) from the river 

 Rhone, France, eight Garganey Teal {Querquedula circia), six 

 Common Teal {Querquedula crecea) European, purchased ; a 

 Thar (Capra jcmlaica, i ), two Black-headed Gulls {Lams 

 ridibundus) bred in the Gardens. 



