476 MR J. Y. BUCHANAN, F.R.S., ON THE 



X. General Analysis. 



A sample of air-dried Loch Fyne nodules was thoroughly extracted with boiling water. 

 The w r eight taken was 5*0405 grammes, and the insoluble portion, when dried at 100°, 

 was found to weigh 4*5458. 



A. Estimation of Moisture. — 0*1910 of the sample was dried at 100°, and found to 

 lose 0*0010 grammes, i.e., the percentage of water in it driven off at 100° is 0*53. 



B. Estimation of the Oxygen reducible by Hydrochloric Acid. — 0*1195 grammes 

 were boiled with strong hydrochloric acid. The chlorine liberated was passed into a 

 solution of potassium iodide, and the amount of iodine liberated found by titration with 

 sodium hyposulphite. There was found to be 4*104 per cent, of available oxygen, 

 representing 22*32 per cent, of Mn0 2 . 



C. Estimation of Weight lost on Ignition. — 0*1263 grammes were strongly heated 

 over a Bunsen flame. The loss of weight was found to be 0*0224 grammes ; that is, 

 17*74 per cent. 



D. Estimation of Insoluble Residue, Fe 2 3 , A1 2 3 , and Co 2 3 . — 2*0880 grammes were 

 treated with strong hydrochloric acid in a covered beaker, the mixture evaporated to 

 dryness over a water-bath, the residue moistened with a few drops of strong hydrochloric 

 acid, taken up with water, and the solution filtered. 



The insoluble residue was heated over the water-bath with a strong solution of 

 carbonate of soda. The heating was carried on for about forty-five minutes, water being 

 occasionally added to keep the solution of constant strength. The solution was then 

 decanted through a filter, more carbonate of soda solution added to the insoluble residue, 

 and the same process repeated. This was done altogether three times. What remained 

 undissolved was washed, ignited, and weighed. It was found to weigh 0*5790 grammes, 

 that is, 27*73 per cent., consisting of silica and silicates, which resist the action of sodium 

 carbonate solution. 



The silica which had dissolved in the sodium carbonate was precipitated from it by 

 hydrochloric acid as usual, filtered, ignited, and weighed. It weighed 0*11928 grammes, 

 that is, 5*71 per cent, of soluble silica. 



The filtrate from the insoluble residue was treated with excess of carbonate of baryta 

 to precipitate the iron and alumina. The precipitate was filtered off and redissolved in 

 hydrochloric acid, the baryta present precipitated with sulphuric acid and filtered off, the 

 filtrate made up to 250 c.c. volume, and two estimations of Fe 2 3 + Al 2 3 made. 



100 c.c. ( = *8352 grammes of substance) gave 0*03368 grammes, Fe 2 3 + Al 2 3 , i.e., 

 4*03 per cent; 75 c.c. ( = *6264 grammes of substance) gave 0*02568 grammes, 

 Fe 2 3 + A1 2 3 , i.e., 4*09 per cent. The two precipitates of Fe 2 3 and A1 2 3 were united 

 and fused with bisulphate of potash. An insoluble residue of silica, weighing 0*00898 

 grammes, was found. This represents 0*61 per cent, of silica in the nodules, which, when 

 added to the previously found 5*71 per cent., gives altogether 6*32 per cent. 



