462 



NA TURE 



[March 20, 1902 



author is peculiarly at home, namely the sections dealing 

 with the gases of the helium group and with liquefaction. 

 On the other hand, the chapter on the preparation of 

 pure gases is somewhat disappointing, not so much 

 on account of what is said as because of what is left 

 unsaid. 



In the introductory fifty pages we notice much valuable 

 information, obviously the outcome of experience, 

 regarding the construction of apparatus, such as 'I'oepler 

 and Sprengel pumps, and practical hints on such matters 

 as the cleaning by means of zinc dust and hydrochloric 

 acid of glass apparatus which has become dirty by long- 

 continued use with mercury. 



While referring to pumps, we may mention that the 

 statement on p. 15 that a filter pump with a good head of 

 water will reduce the pressure in a vessel to the vapour- 

 pressure of water at the time is well inside the mark. In 

 the writer's experience it is not uncommon to obtain by 

 selection a filter pump which will reduce the pressure 

 to much more nearly one millimetre than 15 to 20 mm., 

 the latter being a degree of vacuum quite easily 

 attainable with almost any good pump and moderate 

 pressure. 



For flexible connections to stand high pressures or 

 vacua, the thin weldless steel tubes recommended by Dr. 

 Travers should always be protected by an outer sheath 

 consisting of a compo tube slipped over the steel and 

 drawn tight on to it through several holes of a draw 

 plate. This prevents the steel sufifering, as it is very 

 liable to do, from too sudden bends or from accidental 

 crushing. 



In attempting to preserve for long periods gases col- 

 lected in a sample tube over mercury, great caution is 

 needed in seeing that the surfaces of the tube are quite 

 clean and free from grease, and that the mouth dips well 

 under the mercury in the vessel in which it is placed. 

 Otherwise slow inward diffusion of air may occur along 

 the walls. 



In the chapter on the preparation of pure gases we 

 should have liked fuller descriptions of the methods, and 

 more of them, the details in some cases being decidedly 

 meagre and several of the methods recommended being 

 only suitable for the preparation of very small quantities 

 of gas. 



The electrolytic preparation of hydrogen and oxygen 

 from dilute sulphuric acid is a method which does not 

 receive the author's commendation for ordinary use, but 

 most of the disadvantages disappear, at least in the pre- 

 paration of oxygen, if phosphoric acid is taken in the 

 place of sulphuric. 



No mention is made of the electrolysis of hydrochloric 

 acid and the preparation of the intensely interesting 

 mixture of chlorine and hydrogen sensitive to light, 

 although this experiment is attended with peculiar 

 difficulties. 



On p. 74, reference is made to the " Paris kilogram,'' 

 an ambiguous and unnecessary term if the now almost 

 universally recognised international kilogram is meant 

 (let us be thankful that there are not as many kiloi^rams 

 as ohms), and on p. 130 we find the statement, 



" The results (weighings of gases) are reduced to the 

 values which would have been obtained at sea-level in 



NO. 1690, VOL. 65] 



latitude 45'. They may be reduced to the Paris standard 

 by multiplying by 1000316." 



We fail to see why, after having reached lat. 45 = 

 and sea-level, some charm in the local value of gravity 

 should induce us to come back and reweigh the 

 gas at Paris. It may be mentioned here that the very 

 divergent values quoted on p. 74 for the mass of a cubic 

 decimetre of water at 4^ ought to be replaced by more 

 modern data, which agree in fixing y99'95±o2 grm. as a 

 much more probable value. 



We are glad to see that in the chapter on gas analysis 

 Dr. Travers has weeded out from the many forms of 

 apparatus and methods employed those only suitable for 

 technical use, describing only those capable of scientific 

 accuracy, with copious references to the most recent work 

 on the subject. The usefulness of the chapter would, 

 however, have been increased had a description been 

 given of some form of complete apparatus for general 

 gas analysis, such as that of Prof. MacLeod, or one of 

 its later modifications. 



We may sum up the chapter on the preparation and 

 properties of the gases of the helium group by saying 

 that it contains practically all that is known on the 

 subject. 



Temperature measurement by the gas thermometer is 

 gone into at considerable length ; and the convenient and 

 accurate compensated constant-pressure thermometer of 

 Prof. Callendar is illustrated and its working described 

 in detail. 



In the chapter on the liquefaction of gases, a full account 

 is given of Dr. Travers' own experiments on the liquefac- 

 tion of hydrogen, which is a reprint, with additions, of his 

 recent paper in the Phil. Mag. This concludes with an 

 account of the cost of these experiments, in which it is 

 stated that, after an outlay of about 250/. on the complete 

 plant, an expenditure of about i/. each time covers the 

 cost of making liquid hydrogen. 



Anyone familiar with some of the palatial laboratories 

 of many of the physical chemists abroad, visiting for the 

 first time the dingy dwelling of the chemical department 

 at University College, which the school of Ramsay has 

 now made classic ground, could not fail to be surprised 

 at being shown the hydrogen liquefier fitted up in a 

 disused lavatory, and to hope that in the coming London 

 University scheme physical chemistry may find a worthier 

 home. 



To return to the book, it appears to be accurately 

 printed, and although we have verified many of the 

 numbers and constants given, the errors we have detected 

 are not numerous. 



Among the slips may be pointed out, Kaysir for 

 Kayser ; WUlmer for Wiillner ; KirschotT for Kirchoff. 

 Fig. 102, which is repeatedly referred to, appears to be 

 missing. 



We may conclude by stating how much a study of the 

 book has emphasised in our own mind the importance of 

 Prof. Ramsay's concluding sentence in the preface he has 

 written directing attention to the lacun;c still remaining 

 in many branches of our knowledge, and by heartily con- 

 gratulating Dr. Travers on his labours, which have pro- 

 duced a book worthy of a place in the reference library 

 of every student of modern chemistry. J. \. H. 



