228 ' PRINCIPLES OF CHEMISTRY 



By such and, it may be, other similar indirect methods does gaseous 

 nitrogen yield its primary compounds, in which form it enters into 

 plants, and is elaborated in them into complex albuminous substances. 

 But, starting from a given compound of nitrogen with hydrogen or 

 oxygen, we may, without the aid of organisms, obtain, as will after- 

 wards be partially indicated, most diverse and complex nitrogenous 

 substances, which cannot by any means be formed directly from gaseous 

 nitrogen. In this we see an example not only of the difference between 

 an element in the free state and an intrinsic element, but also of those 

 circuitous or indirect methods by which substances are formed in nature. 

 The discovery, prognostication, and, in general, study of such indirect 

 methods of the preparation and formation of substances forms one of 

 the existing problems of chemistry. From the fact that A does not 

 act at all on B, it must not be concluded that a compound AB is not 

 to be formed. The substances A and B contain atoms which occur in 

 AB, but their state, the nature of their movement and union, may not 

 be- at all that which is required for the formation of AB, and in this 

 substance, although it contains the same elements in mass and quality 

 of them as in A and B, yet their chemical state may be as different as 

 the state of the atoms of oxygen in ozone and in water. Thus free 

 nitrogen is inactive ; but in its compounds it very easily enters into 

 changes and is distinguished by great activity. An acquaintance with 

 the compounds of nitrogen confirms this. But, before entering on this 

 subject, let us consider air as a mass containing free nitrogen. 



Judging from what has been already stated with respect to water, 

 oxygen, ozone, and nitrogen, it will be evident that atmospheric air 



into assimilable nitrogen capable of being absorbed by plants and of forming com- 

 plex (albuminous) substances in them, forms a question of great theoretical and prac- 

 tical interest. The artificial (technical) conversion of the atmospheric nitrogen into 

 nitrogenous compounds, notwithstanding repeated trials, cannot yet be considered as 

 fulfilled in a practical, remunerative manner, although its possibility is already evident. 

 Electricity will probably aid in solving this problem of great practical importance. When 

 the theoretical side of the question is further advanced, then without doubt an advan- 

 tageous means will be found for the manufacture of nitrogenous substances from the 

 nitrogen of the air ; and this is needed, before all, for the agriculturist, to whom nitro- 

 genous fertilisers form an expensive item, and are more important than all other manures. 



One thousand tons of farmyard manure do not generally contain more than four tons 

 of nitrogen in the form of complex nitrogenous substances, and this amount of nitrogen 

 is contained in twenty tons of ammonium sulphate, therefore the action evinced by the 

 mass of manure in respect to the introduction of nitrogen may be produced by sin a II 

 quantities of artificial nitrogenous fertilisers. Over 160000 tons of guano are imported 

 into Europe from South America, because guano (the excrement of sea and other birds) 

 contains many nitrogenous compounds which are required by the agriculturist. 



16 Under the name of atmospheric air the chemist and physicist understand ordinary 

 air containing nitrogen and oxygen only, notwithstanding that the other component parts 

 of air have a very important significance for the vitality of the earth's surface. That air 



