67 



working- with nine soils of the Laterite class common to the Ha- 

 waiian Islands, found a minimum of 67.51 per cent, a maximum 

 of 91.80 per cent, and an average of 82.17 per cent; and Potter and 

 Snyder (1915 a) in seven Iowa soils, found a minimum of 68.68 

 per cent, a maximum of 76.47 per cent, and an average of 74.41 

 per cent. 



The grand average of all of these thirty-seven soils from wide- 

 ly different origin gives 75.91 per cent of the soil nitrogen in solu- 

 tion in the hydrochloric acid extract. In my studies I found a 

 minimum of 66.63 per cent, a maximum of 77.65 per cent, and an 

 average of 72.19 per cent extracted by the acid. 



These results indicate that the nitrogen of practically all soils, 

 in so far as investigated, dissolves to about the same extent during 

 the acid hydrolysis. 



E. "Jodidi numbers." A study of Tables XX, XXI, XXII, 

 XXIII, and XXIV shows that the nitrogen distribution by this 

 method does not give accurate results when compared with similar 

 fractions of the Van Slyke analyses. The ammonia nitrogen and 

 nitrogen in the filtrate from "bases" are all much too high, while 

 "basic N" corresponds fairly well with the true basic nitrogen. 

 If one desires accurate data in regard to the distribution of the 

 organic nitrogen in the soil he should not use "Jodidi numbers." 



F. Attempts to extract proteins from the soil. The attempt 

 to isolate alcohol or salt soluble proteins from the soil was not suc- 

 cessful. The maximum protein nitrogen in the 70 per cent alcohol 

 extract from 6 kilo of soil amounted to. only 0.0010 gram, while 

 the maximum protein nitrogen extracted by the 10 per cent sodium 

 chloride amounted to 0.0280 gram or 17.50 per cent of the total 

 nitrogen in solution. A larger amount of organic nitrogen was 

 extracted by alcohol when the soil was first leached with 1 per cent 

 hydrochloric acid. 



The amounts of possible protein were so small that it seems 

 safe to conclude that no appreciable quantities of alcohol soluble 

 or salt soluble proteins are found in the soil. 



G. A consideration of the nitrogen distribution in different 

 extracts from the sphagnum-covered peat. Nitrogen distribution 

 was determined on extracts of a sphagnum-covered peat soluble 

 in (a) 1 per cent hydrochloric acid, (b) 4 per cent sodium hydroxide 

 and not precipitated by acidification, and (c) 4 per cent sodium 

 hydroxide and precipitated by acidification with hydrochloric acid. 

 Of the three extracts only the second approximates the distribution 

 of nitrogen in a pure protein. The figures for the ammonia nitro- 

 gen are abnormally high in the hydrochloric acid extract. 



The humin nitrogen is high in all the extracts, but is excessive 

 in fraction (c). It is clear that carbohydrates from the soil must 

 be present in all three fractions used, and must have some share 

 in bringing the humin nitrogen up to such high figures. The 

 nucleic acids (Shorey 191 la, 1912) would be found in the hydro- 

 chloric acid precipitate from the sodium hydroxide solution, and 



