468 MR J. Y. BUCHANAN, F.E.S., ON THE 



the flask. This manganese precipitate was then dissolved in a few drops of 

 strong HC1, the chlorine boiled off, and the solution slightly diluted. It was 

 found that the Mn0 2 always brought down some baryta with it, and this was 

 separated by precipitation with a few drops of sulphuric acid. This solution 

 was then filtered from the BaS0 4 ; evaporated to dryness over a water-bath to 

 get rid of all excess of hydrochloric acid ; the residue taken up with water ; 

 the solution filtered again if necessary ; and the manganese precipitated by 

 "pure carbonate of soda solution, only a very slight excess being used. The 

 MnC0 3 was washed first by decantation, then dried, and ignited to Mn 3 4 . 



The filtrate from the MnC0 3 was always kept over-night, when sometimes a second 

 minute precipitate came down. The Mn 3 4 was kept, and the nickel and cobalt in it 

 determined afterwards. 



(b) The filtrate from the Mn0 2 precipitate with bromine was, in the case of the 

 " Challenger nodules," neutralised with NH 4 OH, and then excess of NH 4 HS 

 added, the flask filled up and corked, and allowed to stand for one or more 

 days. Generally a minute black precipitate, accompanied by much barium 

 sulphate, came down. This was filtered off, ignited, dissolved in HC1, the 

 solution evaporated to dryness in a small basin, the residue taken up with 

 water, and preferably a drop of H 2 S0 4 , and filtered. In the filtrate the nickel 

 oxide was precipitated by a drop or two of pure caustic potash. After ignition 

 this precipitate was always tested for purity. It is better, however (and this 

 was done in the case of the Loch Fyne nodule), to neutralise the filtrate from 

 the Mn0 2 with NH 4 OH, add NH 4 HS, and then acetic acid in excess, and pass 

 H 2 S gas through the gently-warmed solution (as is done in the separation of 

 MnO from NiO and CoO). Thus, after standing over-night, minute traces of 

 nickel came down, which remained dissolved in the NH 4 HS solution. 



E. The Mn 3 4 precipitates were dissolved in a few drops of strong HC1 in a small 

 basin, the solution evaporated to dryness over the water-bath, taken up with water, and 

 the solution filtered. To the filtrate, after neutralising any trace of acid present with 

 NH 4 OH, sulphide of ammonium and acetic acid were added, and sulphuretted hydrogen 

 gas passed through the gently-warmed solution to precipitate the nickel and cobalt as 

 sulphides. After standing over-night (the flask being full and corked) this precipitate 

 was filtered off, and the filtrate treated in the same manner with ammonia, ammonium 

 sulphide, acetic acid, and sulphuretted hydrogen. In this way a minute additional 

 precipitate was obtained. The two precipitates were dried, ignited, and dissolved 

 together in hydrochloric acid, and exactly the same process gone through again, so as 

 to get rid of all traces of manganese. The second two precipitates of cobalt and nickel 

 sulphides were again dried, ignited, redissolved in hydrochloric acid, the solution 

 evaporated to dryness, the residue taken up with water, and this solution filtered. The 



