Observations on Liehigs " Organic Chemistrij" loy 



they have absorbed, either in the gaseous form, or in solution 

 in water. The quantity of nitrogen in the atmosphere might 

 lead to the supposition that it might be absorbed and assi- 

 milated as such. The fact of its being absorbable in water, 

 in small quantities only, is against this ; and likewise his 

 finding it in plants in the state of ammonia : unless we sup- 

 pose that the presence of free hydrogen in the plant, from 

 decomposed water, may enable ammonia to be formed bv the 

 action of the living principle ; though it can only be formed 

 chemically in a recent state, when the nitrogen is newly sepa- 

 rated. May not the salts of nitric acid, also, be another source 

 of nitrogen ? The nitric acid requires considerable heat for 

 its formation ; and its salts, nitrate of potash (saltpetre) and 

 nitrate of soda, are more plentifully formed in warm coun- 

 tries,, as India and Peru, from which they form an article of 

 commerce. But saltpetre is largely formed in France, from beds 

 of animal remains in the open air; and, in certain circumstances, 

 where hetit, and lime, and alkalies are present, may not ni- 

 trates of potash or soda be formed in our manure heaps ? or 

 if nitrate of lime is formed, it is one of the most soluble of all 

 the salts of lime. The salts of nitric acid are now much used 

 as manures ; and their only properties, which are said to be 

 great, must be the yielding of nitrogen. 



The nitrogen of plants, in the form of ammonia, he thinks, 

 is got from the atmosphere ; as, notwithstanding all the ni- 

 trogen that is carried off by plants, the new crop of plants 

 still continues to yield nitrogen, which it cannot derive from 

 the soil it exhausts ; and the supply of ammonia is princi- 

 pally from the putrefaction of animal bodies emitting nitro- 

 gen into the air. It forms carbonate of ammonia with the 

 carbonic acid of the air, and is carried to the earth by rain 

 water, and to the leaves in the form of dew. The reason 

 why analysis has failed to detect ammonia in the air, he says, is 

 from the small quantity generally employed for analysis, as 10 

 cubic inches, which would yield only "OOOjOOOjO^S of a grain; 

 but, if a pound of rain water is examined, it will be found to con- 

 tain as much of it as 20,800 cubic feet of air. A field of 40,000 

 square feet, he calculates, will thus receive annually 80 lb. of 

 ammonia, or 65 lb. of nitrogen; calculating 10 lb. of rain water 

 to contain one fourth of a grain of ammonia, and the annual fall 

 at 2,500,000 lb. of rain. This is much more than would be 

 drawn off in the production of the albumen and gluten in wood, 

 hay, or beet root ; but less than by the straw, roots, and grain of 

 corn, which would therefore require a change of crop. Nature, 

 he says, produces sufficient nitrogen for wild plants ; it is culti- 

 vation, or abnormal production, which demands more. Experi- 

 ments made in the laboratory at Giessen, where he is professor, 



