A Z O 



fields of grain and folds of cattle, breaking down their 

 fences, and overwhelming their houfes. Neverlhtk-fs they 

 produce wheat, wine, fruits, and abundance of wood ; and 

 they have many quadrupeds both wild and tame. One of 

 the lateft accounts we Ivdve of thcTe iflands io that of Mr. 

 Adanfon, who vifittd them in 1753, "" ^^^ return from 

 Senegal ; but it is to be regretted, that thefe intcrefting 

 iflands, like all the other Portuguefe fettkments, are almoll 

 unknown. 



AZORIUM, or Azorus, in Ancient Geography, a town 

 of Greece, in Pelagonia Tripolitidii, according to Strabo and 

 Livy. It was fituated among the Perrhsberians, at the con- 

 fluence of two rivers which formed the river Curatius. 



AZOT, in Agricuhun-, a fubftance which is onlv diftin- 

 guifhable in its different Hates of coiiibination with other 

 matters. Its effefts on vegetation, when in the llate of gas, 

 are probably not yet fully afcertained. According to the 

 obfervations of Humboldt and Scopoli, fome forts of plants 

 whenexpofedin it foon droop and iie, while others, as lichens, 

 continue to increafe and grow in a perfect manner. 



AzoT, in Chemifciy, is one of the moil important of 

 the fubftances hitherto conlldered as elementary, exifting 

 very abundantly in nature, forming the greater part of the 

 atmofphcre, the peculiar and almoil chara£terill;ic ingredient 

 of animal matter, the balls of the nitric acid, and one of 

 the conftituents of the volatile alkali. 



Pure or uncombined azot is only known in the form of a 

 gaj; it is then fynonymous with the phlogijVicated air of 

 Scheele and Prieftley, the aimojphencal mephitis of Lavoifier, 

 and the nitrogen gas of Chaptal and fome other French che- 

 niills. 



It was by experiments on the various fubftances which 

 alter, corrupt, and deteriorate common air, that the pro- 

 perties of azotic gas became firfl familiar to chemifts. In 

 all thele, and in the direft eiuliometriciil experiments, or fuch 

 as decompofe the air in order to afcertain its purity, it is the 

 oxygen, together with the carbonic acid and other cafual 

 ingredients, which is fubtrafted by the chemical re-agents ; 

 whilil the azotic gas alone remains unaltered and unablorbed. 

 Hence, chemifts had as firft no other knowledge of azot 

 than as a rcfidue untouched in chemical operations, and its 

 properties could only be defcribed by negatives, till the im- 

 portant difcoveries of the compofition of nitric acid, of am- 

 monia, and of animal matter, gave a new intereft to azot as 

 a chemical element. 



Azotic gas may be obtained in various methods. In ever)' 

 eudiometric procefs, as we have juft mentioned, the refidue 

 is azotic gas of greater or lefs purity. Thus, if phofphorus 

 be burned in a confined quantity of common air, after the 

 cumbuftion has ceafed, the refidue is azotic gas in coiifider- 

 able purity, generally however holding fome of the phof- 

 phorus in folution. 



Another method of obtaining this gas, firft employed by 

 Scheele, is to moiften a quantity of iron filings and fulphur, 

 inclofe them in a glafs velfel full of common air inverted 

 over water, and in a few days by the abforption of all the 

 oxygen of the air, the azotic gas will be left pure. 



Another, and a very fpeedy method of procuring this gas 

 in great purity, is by agitating common air in contaft with a 

 folution of fulphat of iron faturated with nitrous gas. 



Thcfe methods, with the precautions to be obfcrved, 

 will be further noticed under the article EunioMi;TRy, in 

 which it will be fccn that the proportion of azotic gas in 

 the atmofphere is, with little variation, about 73 per cent. 



Azotic gas may alfo be readily procured in large quanti- 

 ties by the decompofition of animal matter by means of ni- 

 tric acid. 

 Vol. III. 



A Z O 



If very dilute nitric acid be poured on any animal matter, 

 pa-.ticidarly mufcular fltfh or the coagulum of blood, ard a 

 gentle heat be ufed, azotic gas is given out in great purity. 

 This experiment is one of a feries of excellent obfervations . 

 on Animal Matter made by BerthoUet, which we have 

 already noticed under that article. The azot in this inllancc 

 procc.ds from the animal matter, and not from the acid. 



In the decompofition of Ammonm.^ by the oxymuriatic 

 acid, and in the reduction of fom.e metallic oxyds by this al- 

 kali, azotic gas is aUb given out in great purity. 



Li a fii;gle inftance, azotic gas may be faid to be mineral, 

 for a very confiderabic quantity of this air rifes up in bub- 

 bles through the fprings of fcveral of rhe native hot fprings, 

 fuch as thofe of Bath and Buxton. The nature of the air 

 thus obtained was firft obfeived by Dr. PrielUey. 



Azotic gas is abfolutcly incapable of fupporting com- 

 buftion. When a lighted taper is dipped in a jar of this 

 air, it becomes inftantly extinguiP.ied without any noife or 

 explofion. It is equally deftrudive to animal life (whence 

 its derivation, from x, and ^m, depriving of life) ; av.d the 

 fatal efFefts to an animal immerfed in it come on fo fpecdily, 

 that it has been thought by fome to puffefs a pofitively 

 noxious power independent of the mere abfence of oxygen. 

 Azotic gas is fomewhat lighter than common air. Its 

 fpecific gravity, when obtained from common air by iron 

 filings and fulphur, is ftated by Kirwau to be 0.0012, or 

 in the proportion of 985 : looo compared with atmofpheric 

 air. Lavoifier makes it only 0.00 1 15, or to common air, 

 as 942. f) : 1000. 



With oxygen, azot forms a variety of combinations. 

 That of atmofpheric air has already been mentioned. A 

 fimple admixture of oxygen with a fmall proportion of azo- 

 tic gas produces no particular effed, but wlicn the combi- 

 nation is afliited by the electric fpark, a true combuftion of 

 azi-t takes phce, and the product is the Nitric Acid. 

 1 his beautiiul difcovery we owe to Mr. Cavendifti. 



When azot and hydrogen are mixed together, both in the 

 gafeous form, no union appears to take place ; but under 

 diff^erent circumftances Ammonia is produced. 



Azotic gas, when heated with Charcoal, with Sul- 

 phur, or with Phosphorus, diffolves a fmall portion of 

 thefe fimple fubftances, and holds them in fufpenfion for a 

 confiderabic time. 



Very little is known concerning the a£lion of azot in its 

 fimple form upon metallic or fal.'iie fubftances ; and in the 

 ftate of gas, it appeais to be more inailive and unwilling 

 to enter into combination than any other fubftance in na- 

 ture. 



Azot has not hitherto boen decompofed, fo that it mull 

 be confidercd as a chemical element. Sevttal attempts, 

 however, have been made for this purpofe, but none of them 

 have proved fatisfaftoiy. The lateft of thefe, which ex- 

 cited much attention in Germany, was that of Wei^leb, a 

 juftly eminent chcmill, an account of which he pubhihed 

 in Crell's Annals for 1796. The chief experiment on 

 which this philofopher grounds his theory of the compofition 

 of azot is the following : if <<n earthen tube of fmall diameter 

 (the Rem of a tobacco-pipe for inftance), be heated quite 

 red-hot, and the fteam of water be fent through the tube 

 in this ftate without any obvious connexion with the exter- 

 nal air, a confiderabic quantity of a gas is generated, which 

 confifts almoft entirely of azotic gas, nixed with a imdll 

 quantity of carbonic acid. Hence, this chemift would infer, 

 tliat as nothing but water and heat are prel'ent, the azotic 

 gas here produced is formed by the union of the vapour of 

 water with caloric at a ver)' high tempirature. A lecond 

 experiment is to pafs the vapour of water over the oxyd of 

 3 G mangancf^ 



