i88 On the Composition of Oceanic 



ammonium molybdate added, and the solution allowed to stand 

 in a warm place till all the phosphoric acid was precipitated. 

 The precipitate was filtered off and dissolved in ammonia, and 

 the phosphoric acid precipitated with magnesia mixture as 

 usual. The precipitate was ignited and weighed. It weighed 

 0-00319 gramme (Mg 2 P 2 O 2 ), representing 0-57 per cent. P 2 O 5 . 



Estimation of Lime and Magnesia. 120 c.c. of the above- 

 mentioned 250 c.c. solution (equivalent to 0-3438 gramme 

 nodules) were treated with sulphide of ammonium, filtered, 

 the ammonium sulphide in the filtrate destroyed by means of 

 hydrochloric acid, evaporated and filtered from sulphur, and 

 the lime precipitated twice with ammonium oxalate as usual. 

 After the 'second precipitation the calcium oxalate (which 

 seemed to contain alumina) was redissolved, and the lime 

 precipitated a third time with ammonium oxalate. The 

 precipitate was filtered, ignited, and dissolved in hydrochloric 

 acid. It weighed 0-0433 gramme. The solution was just 

 rendered alkaline with ammonia. This precipitated the trace 

 of alumina. It was filtered and weighed, and found equal to 

 0-00414 gramme. Subtracting this from 0-0433 gramme, we 

 have 0-03919 gramme of CaCO 3 , that is, 6-38 per cent, of CaO. 



The sulphide of ammonium precipitate, together with the 

 small precipitate of alumina, was worked up for any lime that 

 might be present in it as phosphate. It was ignited, dissolved 

 in hydrochloric acid, the solution evaporated. The phosphoric 

 acid, iron, and alumina present were precipitated by adding 

 acetate of soda. In the filtrate from this the manganese was 

 precipitated with ammonium sulphide. In the filtrate from 

 the manganese sulphide a small additional quantity of lime was 

 obtained on addition of ammonium oxalate ; 0-09154 gramme of 

 CaCO 3 were thus obtained. This is 0-45 per cent, of CaO of 

 the nodules. Adding this to the previously found 6-38 per 

 cent., we have altogether 6-83 per cent, of CaO in the nodules. 



The filtrates from the oxalate of lime were evaporated down, 

 and the ammonium salts driven off. The residue was taken up 

 with hydrochloric acid and water, and filtered. Ammonia and 

 phosphate of soda were added. A precipitate was obtained, 

 which was filtered off, ignited, and weighed as Mg 2 P 2 O 7 . It 



