Chemistry and Physics. 123 



difficult branch of analytical chemistry, and it is also of great 

 value to chemists desiring general information in regard to these 

 important substances. h. l. w. 



4. A Laboratory Manual of Qualitative Chemical Analysis ; 

 by A. R. Bliss, Jr. 8vo, pp. 244. Philadelphia, 1914 (W. B. 

 Saunders Company). — This text- book is intended for the use of 

 students of medicine, pharmacy and dentistiy. As there are 

 many blank pages left for the use of students in making notes, it 

 is not as extensive in its printed contents as its size would indicate. 

 However, it is by no means a brief treatise, and it appears to 

 cover the intended ground in a very satisfactory manner. It 

 gives the analytical processes in tabular form together with rather 

 full descriptions of the tests and operations. In connection with 

 each element its important compounds are mentioned, particularly 

 those included in the U. S. Pharmacopoeia. The book pays prac- 

 tically no attention to chemical equations, although the formulas 

 of the compounds are given. h. l. w. 



5. Absorption and Resonance of Helium. — The recent ex- 

 perimental investigation of the infra-red lines of helium by F. 

 Paschets- has brought to light a number of interesting and 

 important facts. The assemblage of apparatus used comprised 

 thermopiles, interferometers, absorption screens, etc., which do 

 not require special notice in this place. On the other hand, the 

 method which Paschen has perfected for purifying helium merits 

 attention. The successful study of the phenomena of absorption 

 and resonance exhibited by helium required an unusually high 

 degree of purity since the slightest traces of impurities, especially 

 of hydrogen, decrease the absorption. The ordinary methods of 

 purification do not suffice. Helium which has been allowed to 

 remain for a long time in contact with charcoal cooled by liquid 

 air is not pure enough. Paschen's process consists in introducing 

 into the quartz vacuum-tube small quantities of pure oxygen 

 derived electrolytically. At the same time the tube is excited 

 with a " constant" current. The oxygen soon vanishes and with 

 it all other impurities. By repeated additions of oxygen a degree 

 of purity of helium is attained which corresponds to a maximum 

 of absorption. The gas maintains its extreme purity, for a 

 relatively long time, when produced in quartz tubes provided 

 with aluminium electrodes which have been heated red-hot in 

 vacuo. When the absorption begins to decrease, the tube can be 

 brought back to experimental perfection by the introduction of a 

 little more pure oxygen. The author says that a tube, which had 

 been filled with helium at a pressure of about 5 mm , was purified 

 once a week with oxygen during a period of six months. The 

 quantity of helium and the radiating and absorbing powers of 

 this gas at a given current strength remained constant during the 

 interval of time just stated. It is thus clear that Paschen's 

 process makes it possible to rapidly establish with helium exactly 

 reproducible conditions to a degree heretofore unknown with 

 Geissler tubes. The author is as yet unable to account for the 



