98 ■ Scientific Intelligence. 



from 1*86 to 2*97 per cent in 15 samples. The metallic iron was 

 detected by the use of a magnet, but owing to the fineness of the 

 powder it was found to be impossible to remove all of the iron by 

 this means, so that treatment with acid was resorted to. These 

 results are interesting from the large amount of contamination 

 disclosed, which is large enough to affect the results of analysis, 

 even where iron is not considered, to the extent of 2 or 3 parts 

 in 100. The author calls attention to the fact that great care 

 should be used to avoid such errors in cases where grinding 

 machines and " bucking plates " are used for pulverizing hard 

 materials. — Jour. Indust. and Eng. Chem., IV, 6. h. l. w. 



4. Volumetric Determination of Arsenic Acid. — In connection 

 with a study of the compounds of arsenic pentoxide with water, 

 whereby only the previously known compounds As 2 5 .4H 2 and 

 3As 2 6 . 5H 2 are isolated, Menzies and Potter have devised a 

 method for titrating the acid when it is pure and in the free 

 condition. Since the acid, when neutralized, does not give sharp 

 color changes with indicators, the authors add barium chloride 

 to precipitate BaHAs0 4 during the acidimetric titration, using 

 sodium hydroxide solution with phenol phthalein as indicator. 

 It is necessary to use a large quantity of arsenic acid so that 30 or 

 40 cc of normal alkali, which may preferably contain some barium 

 hydroxide, shall be used. 15 cc of saturated barium chloride solu- 

 tion are added, the liquid is diluted to 250 cc , boiled 15 minutes to 

 remove carbon dioxide, cooled, and titrated with phenol phthalein 

 as indicator. The alkaline solution is added with stirring until 

 the locally formed precipitate begins to dissolve slowly, then the 

 walls of the vessel under the liquid are scratched with a glass rod 

 until the liquid appears lustrous with fine crystals, after which the 

 titration is completed as usual. If the conditions are not adhered 

 to, as, for example, if the liquid is too dilute, if the alkali is added 

 too rapidly, or if the stirring is not vigorous enough, very dis- 

 cordant results may be obtained which sometimes approach those 

 required for the precipitation of Ba 3 (As0 4 ) 2 . — Jour. Araer. Chan, 

 Soc, xxxiv, 1457. h. l. w. 



5. Modern Inorganic Chemistry ; by J. W. Mellor, D. Sc, 

 12mo, pp. 871. London, 1912 (Longmans, Green and Co. Price 

 $2.20). — It is a pleasure to review a text-book having so many 

 excellent features as this one. It is a large book, and its treat- 

 ment of the fundamental facts and theories is unusually compre- 

 hensive. It appears to give an abundance of facts for the purpose 

 in view with avoidance of a superfluous number of dry statements. 

 It is written in an interesting literary style and gives many apt 

 quotations, not only from chemical authors but also from ancient 

 philosophers and poets, and even, in one instance, from such an 

 authority as " Sherlock Holmes." Nothing appears to be lacking 

 in the way of a satisfactory presentation of the most modern 

 chemical ideas. Examination questions from all parts of the world 

 are quoted, but it is entirely different from the books which are 

 devised for the sole purpose of preparing for examinations. The 



