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of the alkaline solution in the digestion flask is done by 

 means of a current of steam passing from the steamer 

 through the alkaline solution (with the soil digesting in it), 

 which ultimately gets condensed and drops into the Sulphu- 

 ric acid flask carrying all the ammonia with it. After two 

 hours' further digestion in the alkaline solution, the ammonia 

 all comes out of the soil, and then by titrating the Sulphuric 

 acid in the manner prescribed for the Soda-lime pro- 

 cess, the proportion of N. in the soil, can be inferred, as 

 before. 



1,401. In conducting Nitrogen combustion in the case 

 of highly nitrogenous substances, such as sulphate of ammo- 

 nia, Guano &c., the preparation for combustion should be 

 slightly different. A narrow tube 6" long and closed at one 

 end should be weighed, and about i gram of the substance 

 introduced into it. This tube is inserted after the one inch 

 of soda-lime into the combustion tube, and the rest of the 

 soda-lime filled in as usual but very quickly. 



(5) Potassium. 10 grams more of the soil is weighed 

 out in a Platinum crucible, gently ignited for a few minutes 

 just to carbonize the organic compounds. When cold, 

 it is transferred to a beaker, 50 c. c. of strong HC1 and 

 100 c. c. of water added, the beaker covered up, taken 

 and left for an hour in the sand-bath. The cover is then 

 taken off, and the beaker left in the sand-bath over-night. 

 Next day a few drops of strong HC1 should be added and 

 the mixture kept standing for a quarter of an hour. A little 

 water is then added, and the whole warmed. The processes 

 of drying and boiling are repeated. The Siliceous matter will 

 be probably slightly reddish in tinge. This is filtered out, 

 washed, dried, ignited and weighed. Lime, Phosphates and 

 Potash, besides other things e.g., A1 2 O 3 , Fe 2 O 3 , etc., are 

 dissolved in the filtrate and washings. These are precipi- 

 tated with a slight excess of Ammonia, and left uncovered 

 for an hour or two to get rid of the NH 3 . Aluminium 



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