490 REVIEWS— ELEMENTS OF INORGANIC CHEMISTRY. 



Polarization of Light to chemical investigation, which had not been 

 treated of in the first edition, and which by means of Duboscq's 

 electrical lamp can now be so conveniently made a class experiment 

 and exhibited to a large audience. The elaborate researches of Bunsen 

 and Roscoe on Photo-chemical induction, of Gladstone on Chemical 

 Affinity, of Graham on Osmotic Force, and of Favre and Silzerman on 

 the Heat of Chemical Action, are all, with many others, here repro- 

 duced in a condensed form. 



In the portion of the supplement devoted to the elements we have 

 a tolerably complete account of that difficult and puzzling question, 

 the nature of Ozone, leaving us at its termination nearly in the same 

 state of uncertainty as at the commencement. Mr. "Watts says, "Al- 

 though the existence of an allotropic modification of oxygen seems to 

 be established, the existence of hydrogen in the ozone obtained by the 

 electrolysis of acidulated water can scarcely be denied." This may 

 be so, but it seems rather difficult to imagine that there can be any 

 difference in composition between substances possessing so precisely 

 identical properties as the two ozones thus obtained ; further investi- 

 gations are required on this subject. 



Under the head of the metals of the earths and alkaline earths, we 

 have a full description of the new processes by which these curious 

 bodies have been lately obtained, and by which, for instance, magnesium 

 can be prepared in such quantity and at such moderate expense as to 

 render it available for that most beautiful of all lecture-room experi- 

 ments, the combustion of magnesium in air or oxygen. 



The work, especially the first part, is profusely illustrated with wood 

 engravings, which greatly enhance its value to the student. In look- 

 ing over the drawings of apparatus for the evolution and absorption of 

 ;geses, we have been rather struck with an error, or perhaps more cor- 

 >re.etlv an oversight which occurs in several, and to a remarkable appar- 

 , ent misapprehension of the action of safety tubes. We allude to the 

 ; absence from many of the drawings of the safety tube required to 

 prevent the reflux of the liquid from the washing bottle into the gene- 

 rating flask, and to the erroneous explanation of the action of the wide 

 -tube in fig, 138, page 294. 



In the well known arrangement for preparing pure hydrochloric 

 acid, the generating flask is furnished with a doubly bent tube (Welter's 

 safety tube), containing a little sulphuric acid, and each of the three- 

 necked bottles has a straight tube passing through the centre neck and 



