CONTRACTION AND EXPANSION OF GASES. 65 



It will also be observed, that the volume of 

 phosphorus vapour is augmented from 25 to 100, 

 on uniting with hydrogen, and that of sulphur 

 from 16 to 100, as in sulphuretted hydrogen, sul- 

 phurous acid, &c. 



Here is a most important series of phenomena 

 that have never been explained. 1. Why the 

 specific gravity of gaseous bodies does not always 

 correspond with their atomic weights, except in 

 accordance with the law of multiple or submul- 

 tiple ratios : 2. Why many gases unite chemi- 

 cally with contraction of volume and diminution 

 of elastic force : 3. others without contraction : 

 4. and some with expansion of volume, as the 

 vapours of sulphur, phosphorus, &c. 



It will be shewn in the next chapter, that all 

 the phenomena of contraction, expansion, and 

 the elastic force of gaseous bodies, depend on 

 their relations to caloric, which surrounds every 

 atom of ponderable matter, and, by its transition 

 from one body to another, determines all the 

 chemical or physical changes which they un- 

 dergo ; that the elastic force of hydrogen, oxygen, 

 and nitrogen, (which depends on the relative 

 proportions of caloric and ponderable matter of 

 which they are composed,) is so great, that no 

 degree of force, except that of chemical attrac- 

 tion, has been adequate to condense them per- 

 fectly into the liquid form : but that on uniting 

 chemically with each other, and with carbon, 



