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NATURE 



[June 5, 1913 



graphical research can only be referred to the brochure 

 itself, the seventy pages of which contain much useful 

 and instructive data. Included will be found a number 

 of photographs illustrating various stations, and 

 diagrams showing the method of taking observations. 

 In addition there are four relief maps of the north- 

 eastern portion of Italy (Venice and the adjacent 

 provinces), indicating the scope of operations and their 

 localisation. There is an interesting description of the 

 construction of an experimental tank at Stra. 



POSITIVE RAYS OF ELECTRICITY. 1 



THE first part of the paper contains a discussion 

 - 1 of the evidence afforded by the positive rays 

 as to the nature of the ionisation of the gases in a 

 discharge tube and the properties of atoms. The 

 positive rays consist of : — 



(1) Atoms with one positive charge. 



(2) Molecules with one positive charge. 



(3) Multiply charged atoms. 



(4) Atoms with one negative charge. 



(5) Molecules with one negative charge. 



All the diatomic gaseous elements which have been 

 examined furnish both atoms and molecules with 

 single charges. The proportion of atoms to mole- 

 cules varies very largely with the conditions of the 

 electric discharge, and evidence is given that the 

 charged atoms and molecules are produced by different 

 processes. It is suggested that the ionisation which 

 gives rise to molecules is due to kathode rays, while 

 the charged atoms are produced by the impact of 

 charged atoms and molecules. 



All the elements examined, with the significant 

 exceptions of hydrogen and a substance of atomic 

 weight 3 (X,,), furnish, under certain conditions, atoms 

 with more than one charge. The power of acquiring 

 multiple charges seems to be connected with the 

 atomic weight rather than with the valency or other 

 chemical property of the atom. Thus the atom of 

 mercury, the heaviest atom investigated, can have 

 as many as eight changes, crypton five, argon three, 

 while the lighter atoms, as a rule, have only two. No 

 undoubted case of a doubly-charged molecule of an 

 element or compound has yet been discovered. 



The negative charge is found on the atoms of some 

 elements, e.g. hydrogen, oxygen, carbon, sulphur, 

 chlorine, but not on the atoms of nitrogen, helium, 

 neon, argon, or mercury. It may be regarded as an 

 indication of the chemical activity of the atom, in so 

 far as this depends upon the intensity of the electric 

 field outside the atom. No negatively electrified mole- 

 cules of compounds have been observed ; the only 

 cases of negatively electrified molecules of elements 

 are those of oxygen and carbon, and these onlv occur 

 when the elements are liberated from special types of 

 compounds. 



The second part of the paper deals with the use of 

 these rays as a method of chemical analysis. Several 

 applications of the method are considered. The first 

 of these is to. the detection of rare gases in the atmo- 

 sphere. It is shown that while none of the heavier 

 gases in the atmosphere occurring in quantities com- 

 parable with that of xenon have escaped detection, 

 this is not the case with the lighter gases. 



"Neon," it is shown, is not a simple gas, but a 

 mixture of two gases, containing a large quantitv of 

 a gas of atomic weight about 20, and a much smaller 

 quantitv of one with an atomic weight about 22. 

 The "22" gas was. first observed in samples of resi- 

 dues of liquid air supplied by Sir James Dewar, and 



1 Summary of the Rakerian lecture delivered before the Royal Society on 

 May 22 by Sir J. J. Thomson, O.M., F R.S. 



NO. 2275, VOL. Ql] 



has since been found in every specimen of neon 

 examined, including a specimen supplied by M. Claud, 

 of Paris, and a very 1 arefully purified sample of neon 

 prepared by Mr. Watson. The sample from M. 

 Claud contained a small quantity of a substance with 

 atomic weight 3, the properties of which are dis- 

 cussed later on. 



Another application of this method was to the 

 analysis of the gas in a small glass tube in which 

 30 mg. of radium bromide had been sealed for more 

 than ten years ; in addition to helium, the gas con- 

 tained considerable quantities of "neon" or some 

 element with very nearly the same atomic weight ; 

 there was also a trace of argon in the gas, a little 

 more than would have been expected from the volume 

 of air in the tube, although the difference was not 

 very great. 



The other application of the method is to the inves- 

 tigation of the properties of a substance for which 

 ro/e = 3, X 3 . This gas is given off by most solids 

 when they are bombarded by kathode rays. Reasons 

 are given for concluding that the substance is not the 

 carbon alone with four charges. 



The gas has the following properties : — 



It can pass through tubes containing red-hot copper 

 oxide, and then over potash without being absorbed. 



It is not changed when sparked for a long time 

 with an excess of oxygen, the oxygen being subse- 

 quently removed by phosphorus. 



It can pass over metallic sodium without being 

 absorbed, nor does it disappear when heated along 

 with sodium vapour. 



It is absorbed by charcoal cooled with liquid air, 

 but it can circulate through a glass spiral immersed 

 in liquid air without being condensed. 



It combines with mercury vapour when an electric 

 discharge is sent through the mixture ; it also com- 

 bines to some extent with red-hot copper when passed 

 slowly over it. If stored over mercury vapour it 

 seems to diminish, though very slowly. The gas has 

 been detected after it has been stored for several 

 weeks. 



The study of the positive-ray photograph jndicates 

 that the substance is monatomic, and generally it 

 seems to be similar in its behaviour to the inert gases, 

 although its chemical properties are apparentlv a little 

 more energetic. 



UNIVERSITY AND EDUCATIONAL 

 INTELLIGENCE. 



Cambridge. — Dr. Shipley, master of Christ's Col- 

 lege, has been reappointed representative of the 

 University on the council of the Marine Biological 

 Association. 



On June 3 the Rev. S. A. Donaldson, master of 

 Magdalene College, was re-elected Vice-Chancellor 

 of the University for a second year. 



It is proposed to confer the degree of Doctor of 

 Letters, honoris causa, upon Commendatore Giacomo 

 Boni, director of the excavations on the Forum and 

 the Palatine. 



The registrary reports that the matriculation this 

 term brings the number of new students for the 

 academic year 1912-13 up to 1200. In the last 

 academic year the numbers were 1156. 



Mr. R. "Assheton, of Trinity College, and Mr. L. 

 Doncaster, of King's College, have been approved 

 by the general board of studies for the degree of 

 Doctor of Science. 



Oxford. — A summer course in advanced practical 

 organic chemistry, with demonstrations, will be held 

 at Queen's College, on August 1-30, by Mr. F. D. 



