NARRATIVE OF THE CRUISE. 
1043 
Analysis of Manganese Nodules. 
By Professor W. Dittmar, F.R.S. 
Station 252 ; 2740 fathoms, North Pacific. 
These nodules had a brown or brownish black colour, and, in size and shape, were 
pretty much like potatoes. They were easily broken by the hammer, and then seen to 
consist of a clay-like nucleus enclosed in concentric layers of dark coloured matter, the 
degree of blackness increasing with the distance from the centre. In some cases, 
however, the whole of a section was found to be almost uniformly black. My work 
was limited to exhaustively determining the elementary composition of the nodules, 
and to trying to ascertain, as far as possible by chemical methods, the state of combina- 
tion of the several elements present. In the latter connection I proposed to direct my 
attention more particularly to the manganese, and to ascertain whether this metal were 
present altogether as binoxide, or perhaps partly if not wholly in the form of lower oxides. 
To obtain a true average sample of the nodules, it would have been necessary to pound 
up finely and thoroughly mix the entire stock, but I did not consider myself justified in 
taking this course; I therefore satisfied myself with selecting a few nodules and pounding 
up these. The powder was well mixed and preserved as “ substance to be analysed.” 
A preliminary trial showed that the substance gave up to boiling water nothing but small 
quantities of chlorides and sulphates 1 (which I thought might safely be put down as sea- 
water solids), and besides showed that the filtration of the aqueous infusion was a very 
tedious process. Hence, in proceeding to the actual analysis (which was executed with 
100 grms. of substance), the turbid liquid obtained in extracting the small portion 
of substance soluble in water was simply poured away. The residue was next 
digested in the cold in acetic acid of 25 per cent, until the carbonates of lime and 
magnesia and substances of a similar nature could be assumed to be dissolved, and the 
residue collected on filters and washed with water. This operation was not attended with 
any visible evolution of gas, which, however, does not prove the absolute absence of 
carbonates in the substance. The acetic acid extract was evaporated to dryness and the 
residue (5 ’23 grms.) analysed. Qualitative tests showed the presence of considerable 
quantities of lime, magnesia, and soda, of a little alumina, and of traces of iron, copper, 
and chlorine. There was absolutely no manganese, which proves that the original 
substance could not have contained any manganous carbonate or hydrate. The 
principal bases were determined quantitatively with the following results : — 
Alumina (A1 2 0 3 ), . . . 04 70 x 
Lime (CaO), .... 0 446 ( r iqq parts of original substance. 
Magnesia (MgO), . . . 0-365 f 
Soda (Na 2 0) * .... 0-597 ' 
1 The aqueous extract contained no lime salts, showing the absence of sulphate of lime. 
* Including a little potash. 
(narr. chall. exp. — vol. i. — 1885.) 
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