[ 816 ] 



broken off, and the remainder of the NH 3 , if any, sucked out 

 through the other end. The H 2 SO 4 in the bulb, now par- 

 tially neutralised with the NH 3 coming from the soil, is 

 thoroughly washed out into the beaker containing the residue 

 of the 20 c. c. of the H 2 SO 4 originally taken. This is trans- 

 ferred to a clean porcelain bason ; some Dimethyl Aniline is 

 added as an indicator, and the standard NaHO solution is 

 added from a burette. Suppose it takes 97-2 c. c. of the 

 solution to neutralise the acid completely, then 28 c. c. must 

 have been made up by the NH 3 - 



1,400. The Soda-lime process of estimation of Nitrogen 

 though still commonly followed by agriculturalists, and though 

 for oil-cakes, and nitrogenous manures, this method is suffici- 

 ently accurate, Kjeldahl's process should be followed in the 

 estimation of N. in soils and other substances where it 

 occurs in very minute proportions. In fact, the process 

 is so easy after the apparatus is once set up, and it 

 gives such accurate results, that there is no reason why 

 the Soda-lime method should not be altogether replaced 

 by it. It is adapted for liquid as well as for solid substances. 

 The substance is first heated with strong Sulphuric acid 

 (20 c. c. of Sulphuric acid being used for i gram of soil ), 

 the object being to convert all the Nitrogen in the soil into 

 ammonium sulphate. To raise the temperature of the 

 mixture and to make the dark liquid clear, 10 grammes of 

 dry powdered potassium sulphate are added. The heating 

 is continued for 2 hours after this. By this time the con- 

 version of the nitrogen in the organic substances of the soil 

 into ammonium sulphate is complete. Next an excess of 

 Sodium hydrate solution is added to the digestion flask, 

 and the flask connected with a steamer on the one 

 hand, by means of a bent tube, and on the other, by means 

 of another bent tube with a vertical Liebig condenser. 

 The lower end of the condenser dips into a flask con- 

 taining 20 c. c. of the standard Sulphuric acid. The boiling 



