Chemistry and Physics. 403 



SCIENTIFIC INTELLIGENCE. 



I. Chemistry and Physics. 



1. Prussian Blue and TurnbulPs Blue. — Many investigators 

 have studied the well-known blue precipitates produced on the 

 one hand by mixing solutions of ferric salts with solutions of 

 ferrocyanides, and on the other hand by mixing solutions of fer- 

 rous salts with solutions of ferricyanides, but the compositions of 

 the precipitates thus produced under varying conditions have not 

 been perfectly established. Muller and Stanisch have now 

 undertaken an investigation of this subject by the use of what 

 appears to be a more satisfactory method than has been previ- 

 ously employed. Instead of attempting to isolate and analyze 

 the precipitates themselves, they have determined their composi- 

 tions indirectly by mixing known volumes of solutions of known 

 strength, and after analyzing measured volumes of the clear 

 liquids standing above the precipitates, calculating the composi- 

 tion of the latter. All of the substances were determined volu- 

 metrically by means of permanganate solution — the ferrous iron 

 and the ferrocyanide directly, the ferric iron after reduction with 

 zinc, and the ferricyanide after reduction with a ferrous salt in 

 alkaline solution. Several series of experiments with systemati- 

 cally varying proportions of the reagents gave satisfactory and 

 concordant results leading to the following conclusions : The blue 

 precipitates are all ferrocyanides, whether produced from ferro- 

 cyanide or ferricyanide ; the precipitate Fe'" 4 [Fe // (CN) 6 ] 3 is pro- 

 duced by mixing solutions of ferric chloride and potassium 

 ferrocyanide in molecular proportions ^> 4 : 3 ; the precipitate 

 KFe // Fe'" 3 [Fe // (CN) 6 ] 3 is formed from ferrous chloride and potas- 

 sium ferricvanide in molecular proportions > 4 : 3 ; the precipi- 

 tate KFe'' , "[Fe // (CN) 6 + K 2 Fe // [Fe // (CN) 6 ] is produced from ferric 

 chloride and potassium ferrocyanide in molecular proportions 

 <^ 1 : 1 ; the precipitate KFe'" [Fe // (CN)J is produced from solu- 

 tions of ferrous chloride and potassium ferricyanide in molecular 

 proportions <^ 1 : 1. It is proposed to study in the future such 

 proportions as have not been included here, and also to control 

 the results by the determination of potassium. — Jour, prakt. 

 Chem., lxxix, 81. h. l. w. 



2. The Chemistry of the Radio-active Plements. — The chemi- 

 cal characters of most of the radio-active elements are only imper- 

 fectly known. It has been found that some of them accompany 

 certain well-known elements in precipitations, while others vola- 

 tilize at high temperatures. Whether the volatilized substances 

 are the uncombined elements, their oxides, or other compounds is 

 unknown, while in the case of precipitations the phenomenon of 

 adsorption may play an important part in such exceedingly low 

 concentrations as exist in these cases, so that conclusions in 



