and Littoral Manganese Nodules 189 



weighed 0-03366 gramme, representing 3-53 per cent, of MgO 

 in the substance. Another estimation gave 4-08 per cent, of 

 MgO. 



G. Estimation of Moisture at 162 C. 0-6215 gramme of 

 substance were exposed in a small bath to a temperature of 

 162 C. for about forty minutes. The water driven off was 

 collected in a calcium chloride tube. It was found after 

 heating that the substance had lost 0-0085 gramme (1-37 per 

 cent.), while the calcium chloride tube had gained 0-0098 

 gramme (1-57 per cent.) ; mean, 1-47. 



H. Estimation of Carbon (by combustion). 0-6215 gramme 

 were ignited with pure lead chromate and oxide of copper 

 in a stream of air free from CO 2 . The carbonic acid given off 

 collected in a soda-lime tube, and found to weigh 0-0596 

 gramme, that is, 9-59 per cent. As 8-89 per cent, of carbonic 

 acid as such were found in the substance, this gives us 0-70 

 per cent, of carbonic acid due to organic carbon, or 0-20 per 

 cent, of organic carbon. 



Y. Estimation of MnO and Alkalies. 



5-3893 grammes of the same sample of air-dried Loch Fyne 

 nodules were boiled with water as before, filtered, and the 

 nitrate evaporated. The residue, which crystallised out when 



1 at 110 C., weighed 0-1240 gramme, that is, 2-30 per cent. 

 ie nodules were found soluble in water. The insoluble part 

 was dried at iooC., and separated from the filter-paper. The 

 latter was then ignited, and the ash added to the rest. The 

 whole was th<-n air dried, and this air-dried mass was used for 

 analysis. 



A. Estimation of Moisture (driven off at i5O-i6o C.). 

 0-3609 gramme were heated in a small bath, and the water 

 driven off absorbed by a calcium chloride tube. The heating 

 continued for over half an hour. The substance was found to 

 ii.ive lost 0-0194 gramme (5-53 per cent.), while the calcium 

 chloride gained 0-0183 gramme. The moisture in A is 14; 

 per cent, and in Y 5-53 per cent ; tin* difference is 4-06. There- 

 fore, 95-94 parts of V are equivalent to 100 parts of X, and we 



