No. 7. [From Proc. Roy. Soc. Edin., 1877, Vol. ix. pp. 287-289.] 



NOTE ON THE MANGANESE NODULES 

 FOUND ON THE BED OF THE OCEAN 



THE manganese nodules occur in greater or less quantity 

 all over the ocean-bed, and most abundantly in the Pacific. 

 They occur in all sizes, from minute grains to masses of a pound 

 weight, and even greater, and form nodular concretions of 

 concentric shells, round a nucleus, which is very frequently a 

 piece of pumice or a shark's tooth. Their outside has a peculiar 

 and very characteristic mammillated surface, which enables 

 them to be identified at a glance. When freshly brought up 

 they are very soft, being easily scraped to powder with a knife. 

 They gradually get harder on exposure to the air. 



The powder, heated in a closed tube, gives out water which 

 re-acts alkaline, and has an empyreumatic odour. Heated with 

 strong hydrochloric acid, it liberates abundance of chlorine, and 

 the residue which remains is white, consisting of silica, clay, 

 and sand, the sand being the same as is found in the bottom 

 mud from the same locality. Their composition varies greatly, 

 different nodules containing different quantities of mechanically 

 admixed mud, and the number of different elements found in 

 them is very large. Copper, iron, cobalt, nickel, manganese, 

 alumina, lime, magnesia, silica, and phosphoric acid have been 

 detected in a large number; but I have not as yet been able 

 to make a complete analysis of any of them. I have, however, 

 made a few determinations of the most important component 

 substances. For this purpose the outside and densest layers of 

 the nodules were selected, and portions of them were pulverised 

 and dried for ten or twelve hours at 140 C. The amount of 

 chlorine liberated on treatment with hydrochloric acid was 

 determined by Bunsen's method, and the iron was determined 

 by titration with stannous chloride. The samples analysed 

 were from four different localities. 



