of the Oxides of Manganese. 167 



The material for the preceding analysis was taken from a very 

 fine crystallized specimen from Ihlefeld. The result of GME- 

 LIN'S analysis of the same variety is as follows : Red oxide 

 87' 1, oxygen 3'4, water 9'5. The water js here certainly under- 

 rated. 



The grey oxide from Undenaes in West Gothland, analyzed by 

 ARFWEDSON, is a similar compound. 



Analysis of the Brachytypous Manganese-ore or Braunite. 



The colour of this ore, both in mass and in powder, is nearly 

 black. With sulphuric acid it yields no distinct odour of chlo- 

 rine. It dissolves in muriatic acid, leaving a trace of siliceous 

 matter. The solution gives a precipitate of sulphate of bar, ta 

 with sulphuric acid, but does not contain any other impurity. Of 

 all the native oxides this is the most easily reduced to the state 

 of protoxide by the action of hydrogen gas. The material for 

 analysis formed part of a specimen from Elgersburg. 



As a mean of two closely corresponding experiments, this 

 oxide contains 0*949 per cent of water. 



To ascertain the quantity of oxygen, 16-634 grains were ex- 

 posed for half an hour to the action of hydrogen gas at a red 

 heat. The residue weighed 14-837 grains, and had the light 

 green tint of the protoxide. The total loss was 1'797 grains, or 

 10'80 per cent ; and subtracting 0-949 for water, there remains 

 9'851 per cent as the loss in oxygen. 



The baryta was precipitated by sulphuric acid from a solu- 

 tion in muriatic acid of 42'09 grains of the mineral. The preci- 

 pitate after being heated to redness amounted to 1'44 grains, 

 equivalent to 0'951 of a grain or 2'26 per cent of pure baryta. 



