Notices respecting New Books. 409 



which it cannot be again precipitated. If the solvent contains 

 so much anhydride that crystals are formed on cooling, these 

 crystals are more or less coloured by the green selenium com- 

 pound. The yellow powder dissolves in fuming sulphuric 

 acid, forming a green liquid, which comports itself similarly 

 to a solution of selenium in the same solvent. This liquid, 

 if preserved out of contact with moisture, retains its colour : 

 it is decomposed by water with deposition of the greater part 

 of the dissolved selenium, 94 to 96 parts of selenium being 

 precipitated for every 100 parts dissolved. 



The solutions are decolorized by treatment with solution of 

 sulphurous acid, with oxidation of selenium to selenious acid. 



That the colour of green solutions of selenium in sulphuric 

 acid is due to the formation of the compound SeiS0 3 , and 

 subsequent solution of the same, is shown by the fact that 

 selenium is not dissolved by cold English sulphuric acid, 

 while the compound SeS0 3 is dissolved by this acid with the 

 formation of a green liquid. While dithionic oxide is decom- 

 posed by the first hydrate of sulphuric acid with deposition of 

 sulphur, the analogous selenium compound is dissolved by this 

 hydrate, and even by an acid somewhat more dilute than this; 

 there is a point of dilution, however, at which decomposition 

 takes place. By careful addition of dilute acid to the green 

 solution, it is possible to obtain a brown liquid corresponding 

 with that obtained from a solution of the sulphur compound. 

 This brown liquid is decomposed by further dilution, by 

 warming, or spontaneously after a lapse of some time ; the 

 decomposition is accompanied by the deposition of red sele- 

 nium. The selenium compound dissolves, with the production 

 of a brown-coloured liquid, in sulphuric acid of 1'806 specific 

 gravity, containing about 88 per cent, of the first hydrate. In 

 acid of 1*761 specific gravity, containing about 83 per cent, of 

 the same hydrate, the compound also dissolves; but the brown 

 liquid so produced soon suffers decomposition, with deposition 

 of selenium. 



The author is engaged with an investigation of the com- 

 pounds produced by the action of tellurium and of iodine 

 upon sulphuric anhydride. 



XLIX. Notices respecting New Books. 



A Manual of Qualitative Chemical Analysis. By "William Dittmar, 

 Professor of Chemistry in Anderson's University, Glasgow. Edin- 

 burgh : Edmonston & Douglas. 1876. 



TT was said of Whewell that he had one failing — omniscience. 



-*- In so far as the subject matter of this book is concerned, the 



author appears to suffer under a similar calamity. 

 The book contains too much information — too much, that is, for 



