COMPOSITION OF OCEANIC AND LITTORAL MANGANESE NODULES. 483 



With regard to the available oxygen, 0'5750 grammes were taken, and, after boiling 

 with strong HC1 as usual, the solution of potassium iodide remained colourless. On 

 adding a little starch solution to it, however, a slight purple tint was produced, which 

 the smallest drop of hyposulphite sufficed to decolorise. There is, therefore, only the 

 smallest possible trace of Mn0 2 present, and the 071 per cent. MnO is really present 

 as MnO. 



Analysis of Pecten Shells picked out of the Loch Fyne Mud. 



Qualitative Analysis. — These shells were well scrubbed with pure water, so as to free 

 them from all adhering mud, and then air-dried. They contained — 



Organic matter, . . .A little. 



C0 2 , . . . . .A large amount. 



^ S0 3 , ..... Small amount. 



Si0 2 , ..... Very small amount. 



No metals precipitable by H 2 S in HC1 solution. Very small precipitate with sulphide 

 of ammonium — 



CaO, ..... Very large amount (no BaO). 

 Mgo, ..... Trace. 



Qualitative Estimation of MnO and P 2 5 . — 1'5695 grammes were treated with dilute 

 HC1. There was very little organic* matter present, which shows that the shells were 

 very old. The insoluble residue was filtered, ignited, and weighed ; it weighed 0*0063 

 grammes = "4 per cent, insoluble residue. To the filtrate from the insoluble residue 

 added F1 2 C1 6 and precipitated all the P 2 5 with acetate of soda. In the filtrate from this 

 the manganese was precipitated with bromine. The following results were obtained : — 



Insoluble residue, . . 040 per cent. 



P 2 5 , 009 



MnO, ..... 100 



VOL. XXXVI. PART II. (NO. 17). 4 C 



