Ohservalions on some Comlmations of Azote with Oxygen. 331 



appears to be wanting, as well as foetid limestone. The great 

 compactness and purilv of this salt merit examination. 



Though the country around Cardona is mountainous and 

 rugged, it is inferior in elevation to the districts between it and 

 the Mediterranean ; as well as to those wliich bound it on the 

 north. Immediately behind Cardona the mountains begin to 

 ascend with increasing boldness until they unite with the grand 

 chain of the Pyrenees. 



I relinquish to others the difficult task of giving a probable 

 explanation of the formation of rock salt ; contented if my ob- 

 servations on the mine of Cardona can add any thing to the 

 mass of facts which should guide us in the obscure but captiva- 

 ting speculations of geology. 



LXV. Observations on some Combinations of Azote ivitfi Oxy- 

 gen*. Read to tlie French Academy of' Sciences on the 9lk 

 of Sept. 1815. By Al. DuLONrx. 



V^HEMiSTRY sometimes exhibits combinations so difficult to 

 isolate, and the production of which is accompanied by circum- 

 stances so complicated, that the most expert and accurate ob- 

 servers obtain a knowledge of their pro|)erties onlv after long 

 efforts and successive labours, in which in a manner they ex- 

 punge all knids of errors before attaining the truth. Among 

 those mysterious compounds we may reckon the combination 

 of azote and oxvgen long known under the appellation of vupeur 

 rutiiante {^nilrmis vapour, or nitrous acid s^as). Notwithstanding 

 the numerous researches on this subject, it is onlv since I\I. Gay 

 Lussac's last experiments that the true proportions of it have 

 been known. I had myself made some experiments on the 

 same subject; and as my residts differ in several respects from 

 those obtained by M. Gay Lussac, I shall submit them to the 

 opinion of the public. 



When we distil neutral nitrate of lead previously dried, we 

 obtain a very volatile li(|uid of an orange yellow, which had al- 

 ready been remarked by M. Berzelius in ins researches upon 

 the composition of the nitrates; but which was examined more 

 particularly by M. Gay Lussac, whose researches yielded as a 

 result that tiiis liquid ought to be considered as the acid of the 

 nitrites, in wliich the ekincnts are kept in combination bv the 

 action of the vvater. The existence of water in the dried ni- 

 trate of lead, the proportions of which correspond to those of 

 the nitrates perfectly deprived of water, will present a very sin- 



* Annales dc Cliimk ct dc Tlijuquc, tonic ii. July 181fi; p. 3J7. 



gular 



