182 SOILS: PROPERTIES AND MANAGEMENT 



time. Mulder contended that the organic matter con- 

 sisted of seven distinct compounds, as follows : 



1 and 2. Ulmic acid and ulmin 5. Geic acid 

 3 and 4. Humic acid and humin 6. Apocrenic acid 

 7. Crenic acid 



These bodies he considered as arising from one another 

 by oxidation; thus, ulmic acid (C^HuO^) gave humic 

 acid (C 4 oHi 2 Oi 2 ), which in turn yielded geic acid 

 (C 4 oHi 2 Oi 4 ), followed by apocrenic acid (C^gH^C^), 

 and finally by crenic acid (C24Hi 2 Oi6). Such a classi- 

 fication seems very simple, but certain flaws are at once 

 noticeable. In the first place, nitrogen does not find a 

 place in any of these formulae ; secondly, the compounds 

 are simpler than most plant tissue, which is not what 

 would be expected, especially with some of the degrada- 

 tion compounds; thirdly, none of these products have 

 united with the bases in the soil, a reaction that would 

 be very likely to take place especially with acid compounds. 

 Even the investigators l of Mulder's time obtained dis- 

 cordant results, but these were explained for the time 

 being by assuming that the discrepancies occurred because 

 of added molecules of water. 



Later investigators, while progressing only slightly 

 toward definite results, did accomplish one thing of im- 

 portance, and that was throwing considerable doubt 

 on the old ideas of the Mulder school of chemists. This 

 again opened up the question as to the composition of 

 the soil organic matter, especially the humous constituents. 

 Thus, while it is evident that no such compounds as geic 



1 See Schreiner, O., and Shorey, E. C. The Isolation of 

 Harmful Organic Substances from Soils. U. S. D. A., Bur. 

 Soils, Bui. 53, pp. 15-16. 1909. 



