and Littoral Manganese Nodules 187 



In 50 c.c. of the above-mentioned 250 c.c. solution 0-00676 

 ur.tmme of iron were found by titration with stannous chloride. 

 This is equivalent to 2-31 per cent, of Fe 2 O 3 in nodules. Sub- 

 tracting from 3-45, there remains 1-14 per cent. A1 2 O 3 . 



In the filtrate from the barium carbonate precipitate the 

 manganese was not estimated, but the cobalt was. It was 

 separated by means of sulphide of ammonium and acetic acid, 

 as usual, then precipitated as Fischer's salt with nitrite of 

 potash, and this precipitate dissolved in HC1, and the cobalt 

 n precipitated with a few drops of carbonate of soda solution. 

 It should be mentioned that, before treatment with sulphide 

 of ammonium and acetic acid, sulphuric acid was added to 

 precipitate the excess of barium; to the filtrate from BaSO 4 

 -<>dium carbonate was added to precipitate both manganese 

 and cobalt, and this precipitate dissolved up and the cobalt 

 separated. 0-00049 gramme of Co 3 O 4 were found, representing 

 0-025 per cent, of Co 2 O 3 in the nodules. 



E. Estimation of Carbonic Acid. 0-1792 gramme of 

 nodules were treated with solution of phosphoric acid, the 

 carbonic acid gas liberated passed into baryta water of known 

 strength, and the excess of baryta determined by titration 

 with hydrochloric acid. 0-015905 gramme of Co 2 were found, 

 representing 8-87 per cent, of carbonic acid in the nodules. 



Another estimation was made; 0-1704 gramme of nodules 

 were found to contain 0-015285 gramme of carbonic acid gas, 

 is, 8-91 per cent. 



F. Estimation of Phosphoric Acid. 0-7162 gramme of 

 nodules were converted into chlorides by treatment with HC1 

 (the insoluble residue being removed in the usual way), and 

 the solution made up to 250 c.c. 



125 c.c. of the solution was treated with acetate of soda, 



and the phosphoric acid obtained as a precipitate of ferric 



phosphate. This precipitate was fused with bisulphate of 



potash and the fused mass dissolved in water. There was just 



a mere trace <( in-nlnl>l m.ittrr. 1C this acid solution a very 



lit excess of pure sodium carbonate was added to nrutr.diM- 



ilphuric acid present, .md thru excess of nitric 



lutn'ii w.e> thru evaporated down, large excess of 



