42 



3. Sphagnum-covered peat. Duplicate 15 gram samples were 

 hydrolyzed in the usual manner. It was found in the ammonia de- 

 termination that all of the ammonia nitrogen could not be driven 

 off in a half-hour when the volume of solution was large and a 

 bulky precipitate of 'iron and aluminum hydroxides was present. 

 Continued distillation for a further half-hour in this case gave 

 additional ammonia nitrogen amounting to 0060 gram. In all sub- 

 sequent work with both peats and soils the volume was kept smaller 

 by the use of a more concentrated suspension of calcium hydroxide. 



The calcium hydroxide precipitate containing the "humin" 

 nitrogen was difficult to digest in the subsequent Kjeldahl deter- 

 mination, due to the large amount of carbonaceous organic material 

 present. From 100-200 cc. of sulfuric acid were required for 

 the digestion. After digestion the material was transferred to a 

 1000 cc. flask and 250 cc. portions used for the distillation. It was 

 often necessary to heat the flask on a sand bath to prevent severe 

 bumping. This trouble was obviated in later work by adding zinc 

 dust instead of granulated zinc to the distilling flask. The nitrogen 

 retained by the barium phosphotungstate amounted to 0.0009 gram 

 in Sample I, and 0.0013 gram in Sample II. 



The experimental data showing the grams of nitrogen and 

 per cent of total nitrogen are given in Table VI. 



Table VI. Nitrogen distribution in sphagnum-covered peat. 



Grams nitrogen | Per cent of total nitrogen 



4. Acid "muck" soil One 25 gram sample was hydrolyzed 

 in the presence of 125 cc. concentrated hydrochloric acid for 48 

 hours. The -ammonia nitrogen was determined as usual, and the 

 precipitate of calcium hydroxide containing the '"humin" was 

 washed in a taM soil beaker in the manner described under the 

 method for a mineral soil. After digestion of this precipitate, the 

 material in the !jeldahl flask was diluted to 500 cc. and duplicate 

 distillations made on 250 cc. portions. The bases were precipitated 

 with 15 grams phosphotungstic acid. The total nitrogen retained by 

 the barium phosphotungstate was 0.0022 gram. The solution of 

 the filtrate-from-the-bases was made to a volume of 250 cc. 



