April 8, 1909] 



NA TURE 



175 



Massachusetts, of the isopod crustacean Ancinus depressus 

 ( = Noesa depressa, Say), of which only two examples were 

 previously known. 



To the third part of the Bergens Museum Aarbog for 

 1908 Mr. Alf Wollebcck contributes an important and 

 lavishly illustrated article on the decapod crustaceans of 

 the North Atlantic and the Norwegian fiords. The article 

 commences with an elaborate account, illustrated by eight 

 out of the thirteen plates, of Caloxaris crassipes, for which 

 the new subgeneric term Calocarldes is proposed. The rest 

 of the article is devoted to various species of Macrura, with 

 special reference to their distribution, both horizontal and 

 vertical, and their habits and life-histories. 



In the serial last quoted, No. 1658 (vol. xxxv., pp. 681— 

 727), Prof. C. C. Nutting reviews the alcyonarians of the 

 coast of California, the paper being based on the collections 

 obtained during the cruise of the Albatross in 1904. Oui of 

 a total of thirty-eight species, twenty are referable to the 

 pennatulid group. Many of these species are described for 

 the first time, and the memoir is illustrated with a large 

 number of figures. The writer saw only two kinds of 

 alcyonarians in shallow water — both pennatulids ; and as the 

 coast appears to form an ideal habitat for such organisms, 

 their rarity requires explanation. 



No. 2 of vol. vi. of the Zoological Publications of the 

 University of California is devoted to the Leptomedusae of 

 the San Diego region. Of eleven species of these jelly- 

 fish recognised by the author, Mr. H. B. Torrey, in the 

 collection of the Marine Biological Association of San Diego, 

 no fewer than ten are described as new, two of these indicat- 

 ing new generic types, namely Tiaropsidium and Phialopsis. 



The last paper on our list is the first portion of a 

 memoir by Mr. W. Gariaeff, of the Zoological Laboratory 

 at Villafranca, on the histology of the central nervous 

 system of the cephalopods, published in vol. cxii. of 

 Zeitschrift fUr ■wissenschaftliche Zoologie. In this instance 

 the author deals with Octopus vulgaris. 



T' 



THE INFLUENCE OF MOISTURE ON 

 CHEMICAL CHANGE.^ 

 "HE influence of a trace of water vapour on a chemical 



reaction was first noticed by Prof. H. B. Dixon in 

 _iS8o. He found that it was possible to pass electric sparks 

 in a mixture of carbon monoxide and oxygen without 

 explosion if the mixture had been very carefully dried. 

 Shortly afterwards Cowper proved that dried chlorine had 

 little or no action on several metals. Further observations 

 were made by Prof. Dixon's pupils, the author in 1884 

 showing that carbon could be heated red hot in dried 

 oxygen, that sulphur, and even the very inflammable phos- 

 phorus, could be distilled in the same gas without burn- 

 ing. Later experiments proved that ammonia and hydrogen 

 chloride gases could be mixed without uniting, and that 

 the readily dissociated ammonium chloride could be con- 

 verted into a true vapour, and sulphur trioxide could be 

 crystallised on lime, provided always that moisture was, 

 so far as possible, removed. In 1902 it was shown that 

 tubes containing very dry and pure hydrogen and oxygen 

 could be heated to redness without any explosion resulting, 

 and in 1907 that nitrogen trioxide could exist in the gaseous 

 state if carefully dried. 



Taken altogether, some twenty-five simple chemical 

 actions have been shown to be dependent on the presence 

 of moisture, and a few only, the burning of cyanogen, 

 carbon bisulphide, and some hydrocarbons, seem to take 

 place as easily when dried as 'when moist. In 1893 Sir 

 J. J. Thomson showed that a potential difference of 1200 

 volts was unable to cause the passage of electric sparks 

 through very dry hydrogen, and in the same year the 

 author was able to stop the passage of the discharge from 

 an induction coil by carefully drying the gas between the 

 platinum points. 



The amount of water necessary for the bringing about 

 of chemical action is extremely small, less, in all proba- 

 bility, than one part in three hundred thousand of the 

 reacting gases. Many hypotheses have been suggested for 

 the explanation of its action. Prof. Di.xon believed, in the 

 ' Abstractor the Wilde lecture, delivered before the Manrhe*(<!r Literary 

 and Philosophical Socety on March 0. by Dr. H. Brereton Baker, F.R.S. 



NO. 2058, VOL. 80] 



case of carbon monoxide and o.\ygen, that the water vapour 

 acted as a carrier of oxygen by alternate reduction and re- 

 o.\idation of the hydrogen. Traube imagined an alternate 

 formation and decomposition of hydrogen peroxide. Dr. 

 Armstrong in 1884 suggested a theory of " reversed electro- 

 lysis," the impurity of the water vapour rendering it a 

 conductor. Sir J. J. Thomson in 1893 published a paper 

 showing that if the forces holding the atoms of a molecule 

 together were electrical in their nature, these forces would 

 be very much weakened in presence of liquid drops of any 

 substance of high specific inductive capacity such as water. 



In 1895 it was shown that the newly discovered Rontgen 

 rays were able to cause a gas to become a conductor of 

 electricity, and it was thought, at that time, that the 

 molecules of the gas were split up into atoms by this 

 agency. If this were so, it seemed likely that in these 

 circumstances chemical action would take place in absence 

 of water, but a joint paper of Prof. Dixon and the author, 

 in 1896, showed that the Rontgen rays, at the ordinary 

 temperature, had no measurable effect on the combination 

 of dried gases. Since that time, however, the researches 

 of J. J. Thomson, Rutherford, Townsend, and others have 

 proved that the ionisation of gases is of a different 

 character.' The negative ions are extremely small particles 

 of the mass of about i/ioooth part of the mass of an atom 

 of hydrogen, the positive ion being the residue, but whether 

 it is the residue of a molecule or of an atom seems to be 

 still doubtful. 



With the view of illustrating the influence of ionisation 

 of gases on chemical change, the author devised a new 

 experiment. It is known that mercury vapour, in ordinary 

 circumstances, contains only atoms of mercury, which 

 exhibit little tendency to combine with oxygen. The 

 vapour, however, is ionised in the mercury vapour lamp, 

 and when the current is cut off and oxygen is admitted 

 shortly afterwards, the mercury becomes covered with a 

 la)-er of mercuric oxide. Since the temperature of the 

 lamp is much below that at which ordinary mercury vapour 

 combines with oxygen, it is evident that in this case 

 ionisation can bring about chemical action. 



It is probable that this ionisation of mercury is different 

 from the ordinary ionisation of gases. It may be regarded 

 as the splitting off of an electron from the atom as distinct 

 froin a molecule, and the charged atom of mercury can 

 then enter into union with oxygen. The cases mentioned 

 above of combustions in oxygen which are apparently un- 

 affected by the absence of moisture are perhaps to be 

 explained in the same way. The gases are readily broken 

 up into their elements, and it has been shown that carbon 

 bisulphide breaks up at a lower temperature than that 

 required for its burning. When these gases are heated 

 charged atoms are probably formed, capable of direct union 

 with oxygen. 



To test further the question as to whether the ionisation 

 of molecules, as distinct from atoms, as in the case of 

 mercury vapour, can bring about chemical change, some 

 recent experiments have been performed in which radium 

 bromide was used as the ionising agent. Small quantities 

 of this salt, contained in open silica tubes, were sealed up 

 in tubes containing mixtures of hydrogen and oxygen and 

 carbon monoxide and oxygen, the gases being very dry in 

 some cases and moist in others. In no case was any 

 chemical action observed, although the tubes were allowed 

 to stand at 20° for more than two months. By means of a 

 vacuum gauge the combination of 1/ 10,000th of the whole 

 could have been detected. Another experiment showed that 

 radium bromide was able to produce ionisation in very dry 

 ,air, so that the want of chemical action in the above experi- 

 ments must have been due to the fact that ionisation cannot 

 of itself produce chemical action. There remained, how- 

 r ver, the possibility of ionisation increasing the rate of union 

 of t'.vo gases which were otherwise under conditions which 

 would produce a slow chemical action between them. The 

 reaction between nitrous oxide and hydrogen was found to 

 be a suitable one for investigation, since it takes place 

 1 The author finds that liquid « aler invariably collects in tubes containing 

 salts of radium, though these salts are not at all deliquescent. In one 

 experiment lo m?. of radium bromide increased in weight by 1*5 me. when 

 allowed to stand for two days in an atmosphere saturated with moisture 

 at o" C. Examination of the crystals under the microscope showed that their 

 edees were quite sharp, showing that the absorption of water was not due 

 to deliqu 



