AZOTE. 



AZOTE. 



they readily unite and form the volatile alkali 

 ammonia. 



Azote exists also in gluten ; and wherever 

 this substance is present in vegetable matter, 

 there, in consequence, azote is to be found, 

 but otherwise it does not often enter into the 

 composition of vegetable substances. And yet 

 it is worthy of remark, that although azote can- 

 not be regarded as a direct food of plants, yet 

 most of those substances which contain it are 

 exceedingly grateful to them, such as ammo- 

 nia, saltpetre, animal matter, &c.; and again 

 vegetables certainly emit, and probably inhale, 

 this gas. Thus some plants of Vinca minor 

 being made to vegetate in a confined portion 

 of air for six days, and the composition of the 

 air being ascertained by M. Saussure (Rech 

 Chim. p. 40), the following were the results in 

 cubic inches : 



Azote 

 Oxygen - 

 Carbonic acid 



whe 



- 21l'-92 



- 56-33 



- 21.75 



Composition of atmosphere, 



aken out. 



- 218.95 



- 71-05 



o-oo 



The plants, therefore, had evidently in< 

 creased the proportion of azote and oxygen, 

 but had entirely exhausted the air of its car- 

 bonic acid gas. 



Similar experiments made with the Mcntha 

 aquatica, Cactus opuntia, Li/thrum salacaria, 

 and the Pinus genevensis, afforded similar re- 

 sults. 



Azote, therefore, evidently fulfils a more con- 

 siderable office in vegetable economy than we 

 are yet exactly aware of, and it is more than 

 probable that considerable discoveries are yet 

 to be made in the investigation of its uses to 

 vegetable life. See GASES, their use to vege- 

 tation. (Davy's Chem. Phil. p. 255 ; Thomson's 

 Chem.'} 



[The chief element contained in vegetable 

 substances resorted to for the support of ani- 

 mals, is azote or nitrogen. On the other hand 

 we see, in the vegetable kingdom, plants ap- 

 propriating carbon as the prime element of 

 their structure. The quantity of food which 

 animals take for their nourishment diminishes 

 or increases in the same proportion as it con- 

 tains more or less of the substances yield- 

 ing nitrogen. A horse may be kept alive by 

 feeding it with potatoes, which contain a very 

 small quantity of nitrogen ; but life thus sup- 

 ported is a gradual starvation ; the animal in- 

 creases neither in size nor strength, and sinks 

 under every exertion. The quantity of rice 

 which an East Indian eats astonishes the Eu- 

 ropean or American ; but the fact that rice 

 contains less nitrogen than any other grain, at 

 once explains the circumstance. 



" We cannot suppose," says Liebig, " that 

 a plant would attain maturity, even in the rich- 

 est vegetable mould, without the presence of 

 matter containing nitrogen ; since we know 

 lat nitrogen exists in every part of the vege- 

 '")le structure. The first and most important 

 question to be solved, therefore, is : How and 

 in what form does nature furnish nitrogen to 

 vegetable albumen, and gluten, to fruits and 

 seeds 1 



130 



" This question is susceptible of a very sim- 

 ple solution. 



" Plants, as we know, grow perfectly well in 

 pure charcoal, if supplied at the same time 

 with rain-water. Rain-water can contain nitro- 

 gen only in two forms, either as dissolved at- 

 mospheric air, or as ammonia. Now, the nitro- 

 gen of the air cannot be made to enter into 

 combination with any element except oxygen, 

 even by employment of the most powerful 

 chemical means. We have not the slightest 

 reason for believing that the nitrogen of the 

 atmosphere takes part in the processes of as- 

 similation of plants and animals ; on the con- 

 trary, we know that many plants emit the nitro- 

 gen, which is absorbed by their roots, either in 

 the gaseous form, or in solution in water. But 

 there are, on the other hand, numerous facts, 

 showing that the formation in plants of sub- 

 stances containing nitrogen, such as gluten, 

 takes place in proportion to the quantity of 

 this element which is conveyed to their roots 

 in the state of ammonia, derived from the pu- 

 trefaction of animal matter. 



"Ammonia is a compound gas, consisting 

 of one volume of nitrogen and three volumes 

 of hydrogen. It is produced during the de- 

 composition of many animal substances. It 

 is given off when sal-ammoniac and lime are 

 rubbed together. It was formerly called vola- 

 tile alkali. 



"Ammonia, too, is capable of undergoing 

 such a multitude of transformations, when in 

 contact with other bodies, that in this respect 

 it is not inferior to water, which possesses the 

 same property in an eminent degree. It pos- 

 sesses properties which we do not find in any 

 other compound of nitrogen; when pure, it is 

 extremely soluble in water ; it forms soluble 

 compounds with all the acids ; and when in 

 contact with certain other substances, it com- 

 pletely resigns its character as an alkali, and 

 is capable of assuming the most various and 

 opposite forms." 



With regard to the sources from which 

 vegetables draw those supplies of nitrogen, so 

 ssential to their growth and developement, 

 Liebig makes the following observations : 



Let us picture to ourselves the condition 

 of a well-cultured farm, so large as to be in- 

 dependent of assistance from other quarters. 

 On this extent of land there is a certain quah- 

 ity of nitrogen contained both in the corn and 

 ruit which it produces, and in the men and 

 animals which feed upon them, and also in 

 heir excrements. We shall suppose this quan- 

 ity to be known. The land is cultivated with- 

 mt the importation of any foreign substance 

 containing nitrogen. Now, the products of 

 his farm must be exchanged every year for 

 money, and other necessaries of life, for bodies 

 herefore which contain no nitrogen. A cer- 

 ain proportion of nitrogen is exported with 

 corn and cattle; and this exportation takes 

 lace every year, without the smallest com- 

 pensation ; yet after a given number of years, 

 he quantity of nitrogen will be found to have 

 increased. Whence, we may ask, comes this 

 increase of nitrogen 1 ? The nitrogen in the 

 excrements cannot reproduce itself, and the 



