Oceanic Manganese Nodules 



159 



Nos, 2, 4, and 5 were from the same place, No. 2 being the 

 matter collected round a shark's tooth as nucleus ; Xos. 4 and 

 5 being the outside rinds of ordinary nodules. 



The results are given in the following table, the numbers 

 being in many cases the means of several observations: 



A is the residue which remains undissolved after treating 

 the mineral with strong hydrochloric acid, evaporating to 

 dry ness and redissolving. In Xo. 5 it contains 85-16 per cent, 

 silica, and in No. 6, 82-27 P er cent . 



B is the " available oxygen" determined by Bunsen's method. 



C is the MnO 2 equivalent to the available oxygen. 



/> is the MnO found by weighing as Mn 3 O 4 . 



E is the Fe 2 O 3 found by titration with SnCl 2 . 



F is the alumina found by subtracting the Fe 2 O 3 found in 



rom the weight of the precipitate with acetate of soda. 



G is the water expelled on ignition ; it is obtained by 

 deducting two-thirds of the oxygen found in B from the loss 

 of weight by ignition. 



It will be seen from the results given in the above table that 



the nodules from different local itirs vary greatly in composition, 



though in the same locality thrv have similar composition. 



pectively of tin natuie of the nodules. The insoluble 



.tie contains, besides silica and clay, sand of the same mineral 

 nature as is found in the bottom at the same lo< alitv. The 



Ljanese is present wholly as MnO 2 , an<l th- iron as FcjOj. 

 In Xo. C) th'-re is 0*3 per "lalt : this m.-tal. al-m- \\ith 



copper and a little niekel. is present in all of them. Zinc 

 not found in any of the above spccinn 



