and Littoral Manganese Nodules 193 



were (after the moisture had been driven off) extracted with 

 hot water. The solution was evaporated to dryness, ignited, 

 and weighed. It weighed 0-0169 gramme, that is, 2-09 per 

 cent, of the nodules. 



The dry residue was redissolved and tested for potash, and 

 found to contain a little. 



C. Estimation of Insoluble Residue, Manganese, Iron and 

 Alumina. Treated what was insoluble in water of the above 

 0-8078 gramme with hydrochloric acid, and separated the 

 silica and silicates as usual. The insoluble residue weighed 

 0-26106 gramme, equal to 32-32 per cent. 



The filtrate from the insoluble residue was made up to 

 100 c.c. 50 c.c. of the solution (equal to 0-4039 gramme of 

 nodules) were used for manganese estimation, and 0-1349 

 gramme of Mn 3 O 4 found. This gives 31-11 per cent, of MnO. 



The iron and alumina were precipitated by barium carbonate 

 in 100 c.c. of the solution. (It was the filtrate from this 

 precipitate that was used for the manganese estimation.) 

 The precipitate was redissolved in hydrochloric acid, the 

 baryta present precipitated with sulphuric acid, and iron and 

 alumina precipitated from the nitrate from the barium sulphate. 

 0-0146 gramme of Fe 2 O 3 -h A1 2 O 3 was found, representing 

 3-60 per cent, in the nodules. This was fused with bisulphate 

 of potash, and found free from silica. 



To make the figures comparable with those of X, we have 

 2-09 soluble matter and 4-05 moisture, together 6-14; from 

 \\liirh we deduct 1-47 moisture in X, leaving 4-67; whence 

 95*33 of Z are equivalent to 100 of X. We must therefore 

 multiply the figures obtained in Z by 1-049. We have then 

 MnO = 32-62 per cent., insoluble residue = 33-90 per cent., 

 and Fe 2 O 3 + A1 2 O 8 = 3-77 per cent. After making all 

 reductions we have 



Insoluble Residue. In X 34-05 per cent., and in Z 33-90 

 per cent. As the soluble silica was determined in A", and the 

 value of the total residue in Z agrees closely, we take the values 

 for A", namely, soluble SiO 8 6-32 per cent., and remainde: 

 ue 27-73 together, 34*05 per cent. 



Fe 2 O 8 and A1 2 O 3 . As the figure found in Z for the sum of 



B. in. 13 



