Notices respecting New Boohs. 509 



precipitation duly in prominence, and may form a fair estimate of 

 the work that lies before him if he essays their separation. Since 

 this chapter was written, much doubt has been thrown upon the 

 homogeneousness of Didymium. Samarium is, of course, a new 

 feature here ; and Thorium is an additional entry. Under Glucinum 

 we wish it could have been possible to say something of Mr. Greville 

 Williams's experiments. The detailed exposition of Mr. Crookes's 

 own researches on the detection and wide distribution of Yttrium 

 is extremely interesting, and constitutes an admirable guide for a 

 young investigator. Other rare earth-metals are referred to in 

 considerable detail, none in fact being omitted. One can hardly 

 read the account of Titanium and Zirconium without seeing that 

 pure compounds of the former metal can hardly have been yet 

 prepared. The results of Pierre and Thorpe as to the combining 

 weight of the former element are hopelessly discordant, and yet, 

 on the face of them, equally trustworthy. The volumetric esti- 

 mation of Chromic Acid by adding an iodide and hydric chloride is 

 liable to considerable error if allowed to consume " a few hours," as 

 stated in the text. The reviewer uses strong hydrochloric acid 

 diluted with an equal bulk of water and heated to 50° : titration 

 can then be proceeded with at once. Manganese ores can be valued 

 in the same way, after a contact seldom exceeding 15 minutes. 

 The whole section on Iron (nearly 90 pages) is admirably written, 

 the requirements of technologists being evidently borne well in 

 mind. Here the Author appears to us to have been adding and 

 selecting at his best. The entire chapter deserves the most careful 

 perusal. As regards Eggertz's method, we have always considered 

 its weak point to be the dilution, which necessarily affects the 

 constitution of all liquids, and may be the source of grave error. 

 The best colorimeter to employ in this case is one of the forms 

 for which dilution is not necessarily required. Clark's method of 

 analyzing chrome-iron ore is certainly the best. Many of the 

 failures in analyzing this ore are not the fault of any particular 

 method, but of overheating. In the separation of Cobalt from 

 Nickel, it would have been an advantage if Gibbs's simple and per- 

 fectly accurate plan of boiling the aqueous sulphates with plumbic 

 peroxide could have been inserted. As regards Copper, we could 

 wish the volumetric cyanide process were a thing of the past. 

 Sulphur in pyrites has been the bete noire of many analysts. Mr. 

 Crookes commends Pearson's method, which is doubtless the best ; 

 the reviewer, however, prefers to carry out the early stages of the 

 attack at 30°-40°, not at 100°. It is curious that JNakamura's 

 method should fail for pyrites. "We are glad to see Gibbs's elegant 

 phosphate process given for Manganese. Few analysts practise it ; 

 but we hope Mr. Crookes's description may induce many to use it 

 habitually. We have nothing but praise for the section on Gas 

 Analysis, which is quite full enough, though succinctly written. In 

 the Tables, we could have wished that Captain Clarke's figures had 

 been employed as the basis of metric equivalence. 



Some omissions ought perhaps to be noticed. In our opinion, a 



