32 OF THE ASSIMILATION OF CARBON. 



potash upon sawdust contains, according to the 

 accurate analysis of Peligot, 12 per cent, of carbon, 

 while the humic acid obtained from turf and brown 

 coal contains, according to Sprengel, only 58 per 

 cent. ; that produced by the action of dilute sul- 

 phuric acid upon sugar, 57 per cent, according to 

 Malaguti ; and that, lastly, which is obtained from 

 sugar or from starch, by means of muriatic acid, 

 according to the analysis of Stein, 64 per cent. All 

 these analyses have been repeated with care and 

 accuracy, and the proportion of carbon in the re- 

 spective cases has been found to agree with the 

 estimates of the different chemists above mentioned; 

 so that there is no reason to ascribe the difference 

 in this respect between the varieties of humus to 

 the mere difference in the methods of analysis or 

 degrees of expertness of the operators. Malaguti 

 states, moreover, that humic acid contains an equal 

 number of equivalents of oxygen and hydrogen, that 

 is to say, that these elements exist in it in the pro- 

 portions for forming water ; while, according to 

 Sprengel, the oxygen is in excess, and Peligot even 

 estimates the quantity of oxygen at 14 equivalents, 

 and the hydrogen at only 6 equivalents, making the 

 deficiency of hydrogen as great as 8 equivalents. 

 And although Mulder * has very recently explained 

 many of these conflicting results, by showing that 

 there are several kinds of humus and humic acids 

 essentially distinct in their characters, and fixed in 

 their composition, yet he has afforded no proof that 

 the definite compounds obtained by him really exist, 

 as such, in the soil. On the contrary, they appear 

 to have been formed by the action of the potash and 

 ammonia, which he employed in their preparation. 



It is quite evident, therefore, that chemists have 

 been in the habit of designating all products of the 

 decomposition of organic bodies which had a brown 

 or brownish-black, color by the names of humic 



* Bulletin des Scienc. Phys. et Natur. de Neerl. 1840, p. 1-102. 



