278 Scientific Intelligence. 



SCIENTIFIC INTELLIGENCE. 



I. Chemistry and Phy 



SICS. 



1. The Quantitative Determination of Manganese in the Form 

 of Various Oxides. — Raikow and Tischkow have found that the 

 higher oxides of manganese are reduced to MnO by ignition in a 

 stream of hydrogen in a Rose crucible. The reduction is has- 

 tened to a certain extent by increase in temperature, but it depends 

 chiefly upon the speed of the stream of hydrogen, so that with a 

 rapid stream of hydrogen the reduction is complete in a few min- 

 utes, even with the moderate heat of a Teclu burner, and the MnO 

 is entirely homogeneous and of a pale green color. This novel 

 form for weighing manganese is recommended by the authors as 

 one of the most accurate. 



The conversion of manganese oxides into Mn 3 4 has also been 

 studied. It was found that MnO is converted quantitatively into 

 the protosesquioxide by ignition in the air over the blast-lamp, 

 but that, if the temperature is not high enough, oxidation to Mn 2 3 

 gradually takes place. However, by igniting a higher oxide in a 

 stream of dry carbon dioxide in a Rose crucible with a Teclu 

 burner, pure Mn 3 4 is obtained, and this method of weighing 

 manganese is also recommended as accurate. 



The authors have found that the oxides of manganese, when 

 heated in the air for a long time by means of a Bunsen burner, 

 are quantitatively converted into Mn 2 3 , and that this conversion 

 takes place more rapidly in a stream of oxygen. The conversion 

 of manganese carbonate into Mn 2 3 can be accomplished by heat- 

 ing in an oxygen atmosphere, at first strongly with a Bunsen 

 burner, and then at a red heat. The Mn 2 3 is deep black and 

 entirely homogeneous. The conversion of manganese sulphate 

 into Mn 3 is not so simple. It must be ignited alternately for 

 about 5 to 10 minutes in hydrogen and then in the air, and when 

 no more S0 2 is given off by ignition in the air it can be brought 

 into the form of Mn 2 3 by ignition at a red heat in oxygen. — 

 Zeitschr. analyt. Chem., li, 135. h. l. w. 



2. A Pernitride of Carbon. — G. Darzens has announced the 

 preparation of cyanogen trinitride, CN 4 , which according to the 

 present views has the structural formula 



|j N_C = N 

 N^ 



The compound was easily prepared by the reaction of sodium 

 trinitride with cyanogen bromide in aqueous solution. 



NaN 3 + BrCN = N 3 CN + NaBr. 



