582 



FRIDAY, SEPTEMBER 2. 



The folio-wing Report and Papers -were read : — 



1. Second Report of the Committee upon the present state of our Knotvledge 

 of Spectrmn Analysis. — See Reports, p. 317. 



2. On the Fluid Density of certain Metals. 

 By Professor W. Chandler Roberts, F.B.S., and T. Wrightson. 



3. On the Oxides of Manganese. By V. H. Velet, B.A. 



The author at the outset gave an historical account of researches on the oxides 

 of manganese, in order to sho-w lio-w far it has heen satisfactorily proved by them, 

 firstly, that manganese forms with oxygen a series of definite oxides (apart from 

 those present in manganic and permanganic acids), and secondly, that manganese 

 dioxide forms a series of hydrates. The researches of Dittmar, Wright, and others, 

 on the conditions of formation of these oxides, and their behaviour when heated to 

 various temperatures in certain gases, is also noticed. 



The author had studied the action of air, oxygen, nitrogen, and hydrogen at 

 temperatures ranging from 60° to 200° C. on an oxide of formula MngOjj, and has 

 prepared and analysed the following higher oxides and hydrates. 



Wlien the oxides are heated in air or oxygen at low temperatures two changes 

 are observed : 1st, a loss of water of hydration ; 2nd, an absorption of oxygen. Wlien 

 heated in nitrogen they are dehydrated ; but do not, as at higher temperatures, lose 

 so-called available oxygen. When heated in hydrogen they are simultaneously de- 

 hydrated and reduced. The author inclined to the view that these oxides are dis- 

 tinct chemical entities, and are not mere combinations of molecules (molecular 

 compounds). The author is carrying on further researches on the oxides of manga- 

 nese in order to study more completely the conditions of formation, of temperature, 

 tension of oxygen and other gases of each separate oxide and hydrate ; and hopes 

 thereby to arrive at a more intimate knowledge of the constitution of the metallic 

 oxides. 



4. On the Inferences deducible from high Molecular Weights, as exhibited by 

 tJie Oxides of Manganese. By Professor W. Odling, F.B.S. 



