NARRATIVE OF THE CRUISE. 
1047 
I know of no test for discriminating between free manganese binoxide and manganese 
binoxide combined with oxides of the type R r/ 0 ; but what can be done in a case like the 
one in hand is to determine the exact ratio of the “ MnO ” present in all to the loose 
oxygen present. But a complicated complete analysis like the one reported, however 
carefully -done, cannot possibly supply sufficiently exact data for this purpose. 
I therefore selected from my stock a nodule which seemed to be exceptionally rich 
in manganese, and determined, by a specially devised process, the total manganese, as 
manganous oxide, and (by the ordinary methods) the loose oxygen. 
To determine the total manganese, a weighed quantity of homogeneous substance; 
was disintegrated by hydrochloric acid, the iron and alumina precipitated by means of 
acetate of soda and filtered off, and from the filtrate the manganese precipitated by means 
of bromine in presence of zinc salt. The precipitate (which contained all the manganese 
as binoxide) was dissolved by dilute sulphuric acid in an atmosphere of carbonic acid with 
a known weight of standardized ferrous sulphate and the excess of “ ferrosum ” titrated 
by permanganate. That this method, which every chemist will recognise as a slight 
modification of Kessler’s, gives exact results had been proved by a series of experi- 
ments on known weights of manganese given as a solution of pure chloride which had 
been standardized by means of nitrate of silver. 
In the analysis of the nodule two determinations gave — 
I. II. Mean. 
16-54 16-30 16-42 
per cent, of manganous oxide (present as MnO . O x ). 
be as follows : — ■ 
Iodine method, ...... 
Oxalic acid method, * . ... . 
The loose oxygen was found ter 
Mean. 
3-775 3-764 3-77 
3-85 3-95 3-90 
Dividing by the combining weights we have — 
16-42 : 35-5 = 0-4626 
3-77 : 8-0 = 0-4712 
3-90: 8-0 = 0-4874 
Here the oxygen found is a' little more than what would be sufficient to convert the 
manganous oxide into binoxide. Possibly some of the loose oxygen may have been 
present as peroxide of cobalt (Co 2 0 3 ) ; but I have had no time yet to inquire further 
into the matter experimentally. All I can say is that the determinations were made with 
great care at a time when we had become very familiar with all the manipulations 
involved, and I think I am safe in asserting that that particular nodule in all probability 
contains its manganese in the form of binoxide only. 
* 0‘877 grm. of the substance when decomposed by acid (with ferrous chloride) gave less than 1 mgrm. of carbonic acid. 
