Dr. Turner's Examination of the Oxides of Manganese, 23 



came quite dry. The salt thus prepared yielded a colourless 

 solution, without any residue, when put into dilute sulphuric 

 acid, and was therefore free from the red oxide of manga- 

 nese. 



Of this carbonate 8*805 grains were heated to redness in a 

 green glass tube, and the water collected in a tube filled with 

 fragments of the chloride of calcium. The quantity of water 

 procured in this way amounted to 0*742 of a grain, equivalent 

 to 8*427 per cent. 



The proportion of carbonic acid was estimated by noting 

 the loss of weight which the carbonate of manganese experi- 

 ences when dissolved in dilute sulphuric acid. This mode of 

 analysis, as commonly performed, is inaccurate ; because the 

 liquid retains carbonic acid in solution, while the gas during 

 effervescence carries off with it an appreciable quantity of wa- 

 tery vapour. But when performed with the precautions which 

 I adopted, it yields uniform results, and is susceptible of great 

 precision. A known quantity of the carbonate is placed in a 

 small glass phial fitted with a tight cork, in which two tubes 

 are inserted. One of these tubes descends to near the bottom 

 of the phial and then bends slightly upwards, so as to admit 

 of the acid being gradually introduced without affording an 

 exit to the gas. The other communicates with a tube filled 

 with chloride of calcium, over which all the carbonic acid gas 

 passes before escaping into the air. As soon as the efferves- 

 cence has ceased, the carbonic acid retained by the solution 

 is driven off by causing it to boil during the space of a few 

 minutes ; and the gas is by the same means expelled from the 

 interior of the phial, into which on cooling the atmospheric 

 air is admitted by the tube for introducing the sulphuric acid. 

 The carbonic acid gas remaining with the chloride of calcium 

 is replaced by atmospheric air, which is introduced by in- 

 haling at one extremity of the tube while the other is open. 

 The upper part of the tube for introducing the dilute sul- 

 phuric acid, when not required to be open, is of course closed 

 with a cork in order to avoid loss by evaporation. 



It was found by means of the preceding process that 20*68 

 grains of the carbonate, when dissolved in dilute sulphuric 

 acid, lose precisely 7*18 grains, or 34*72 per cent of carbonic 

 acid. It is accordingly composed, in 100 parts, of 



Protoxide of manganese 56*853 



Carbonic acid 34*720 



Water 8*427 



100*000 



Regarding 



