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XXIV. Sequel to anEssay on the Constitution of the Atmosphere, 

 published in the Philosophical Transactions for 1826; *ix)ith 

 some Account of the Sulphurets of Lime. By John Dalton, 

 D.CL,, F.R.S. Sfc* 



IN an essay of mine on the constitution of the atmosphere, 

 which was printed in the Transactions for 1826, I signified 

 my intention of following it with a sequel of experiments to 

 ascertain if possible which of the two views therein developed 

 was most countenanced by facts. I now proceed to give an 

 account of such investigations relating to this subject as have 

 engaged my attention during a long period of years. 



It may be needful to premise certain facts which are, I be- 

 lieve, universally admitted as indisputable; namely, that the 

 atmosphere consists principally of two elastic fluids, azote and 

 oxygen, either mixed by some mechanical law, or otherwise 

 combined by a chemical principle in proportion nearly as four 

 parts of the former to one of the latter in volume ; that the 

 two elastic fluids may be obtained separately in a state of 

 purity; that when thus obtained they may be mixed in all 

 possible proportions; and that the aggregate volumes in 

 such cases are just equal to the sum of the two volumes of the 

 ingredients ; also, that any body which has a chemical affinity 

 for either of them, so as to combine with it in a separate state, 

 will also combine with it in the mixed state. 



It is also pretty generally admitted that oxygen and azote 

 are capable of chemical combinations in five or more definite 

 proportions, namely, 



2 vol. of azote with 1 vol. of oxygen — forming 2 vol. of 

 nitrous oxide. 



1 vol. of azote with 1 vol. of oxygen— forming 2 vol. of 

 nitrous gas. 



1 vol. of azote with 1| vol. of oxygen — forming I^ vol. of 

 hyponitrous acid. 



I vol. of azote with 2 vol. of oxygen — forming 2 vol. of 

 nitrous acid vapour. 



1 vol. of azote with 2^ vol of oxygen — forming 2| vol. of 

 nitric acid. 



There does not appear to be a doubt of the reality of five 

 combinations, but all chemists are not agreed as to the pro- 

 portions of the volumes being precisely as above specified, 

 chiefly because no general law has been found to obtain in 

 such gaseous compounds. 



These compounds are never formed nor decomposed with- 

 out manifest chemical agency; they all contain oxygen, but 



• From the Philosophical Transactions, 1837, Part ii. : an abstract of Dr. 

 Dalton*s former paper will be found in Phil. Mag., First Series, vol. Ixvii., 

 p. 310. 



