100 Observations on Liebig's " Organic Chemistry.^' 



calculates that only 61 lb. of humic acid would be taken up by 

 the alkalies ; which, at 58 per cent of carbon in humic acid, and 

 38 per cent of carbon in wood, is equal to 91 lb. of wood that 

 would be produced in 40,000 square feet, in place of 2,6.50 lb., 

 Dr. Heyer's quantity. As qualifications however of this proof, 

 it may be stated, that the analysis is of dry fir wood ; and, by his 

 own statement at page 108., the leaves and bark, and small 

 branches, contain the greatest part of the alkalies in trees. The 

 leaves of firs he states as containing 8 per cent of alkalies; and, 

 if these are neglected in the analysis of the wood, as it appears 

 they have been, it would make a very material difference in the 

 estimate. 



He also states that it has been taken for granted, in these 

 calculations, that the alkalies which served to introduce the 

 humic acid into the plants do not I'eturn to the soil, since it is 

 certain that alkalies remain fixed in the parts newly formed dur- 

 ing the period of growth. On this head it may be observed, 

 that, though alkalies are found forming part of the plant, and 

 therefore necessary to their existence, yet, as staled at page lO^,, 

 they will certainly be rejected as excrements when not needed, 

 as all articles not necessary are. At page 102. he says, the ele- 

 ments of substances may be retained, and the rest returned ; and, 

 at page 156., from the decreasing quantity of ashes found by De 

 Saussure in the analysis of wheat, as it continued to ripen, it 

 appears evident they are so returned. All the alkalies and other 

 matters in excess will be so returned as excrement; and humate 

 of lime or carbonate of potash may be separated into their ele- 

 ments in the plant, the carbonic acid retained, and the lime and 

 potash returned, to be again neutralised and absorbed. He 

 next calculates the quantity of humic acid that would be taken 

 up by rain water, on 40,000 square feet; and, estimating the 

 water at 700,000 lb. of rain, from April to July inclusive, and 

 the humic acid being soluble only in 2,500 times its weight of 

 water, though the whole of the water should be taken up by the 

 plants on the soil, there would not be assimilated above 300 lb. 

 of carbon by this means. 



He next calculates the quantity of carbon produced from 

 the growth of different plants in the same quantity of ground ; 

 which he estimates at 1,007 lb. of carbon for wood and meadow 

 land, 936 lb. for beet root, and 1,020 lb. for corn : thus 

 showino; that neither alkalies nor rain water can render solu- 

 ble a sufficient quantity of humic acid, to furnish the quantity 

 of carbon requisite. If, however, we allow that the neutral 

 salts are taken up by the roots ; if the carbonates of potash, 

 soda, &c., formed in the manure and in the soil, are taken 

 up, the carbonic acid (which has, in some cases, the property 

 of uniting with the bases in two or three proportions,) extracted 



