108 COMBINING PROPORTIONS. 



These numbers prove to be in some degree characteristic of 

 the substances to which they are here attached, for when the 

 composition of the sulphurets of the same substances is ex- 

 amined, it is found that exactly corresponding quantities of 

 hydrogen, copper, &c. likewise combine with one and the same 

 quantity of sulphur, although not with 100 parts of that element 

 as of oxygen. The conclusion from an examination of the 

 sulphurets is, that 



12.5 parts of hydrogen, 



3.96 parts of copper, 



403 parts of zinc, 



1 294 parts of lead, 



1352 parts of silver, 



combine with 201 parts of sulphur. An examination of the 

 chlorides of the same five elements likewise proves, that 



12.5 parts of hydrogen, 



396 parts of copper, 



403 parts of zinc, 

 1 294 parts of lead, 

 1352 parts of silver, 



combine with 442 parts of chlorine. Hydrogen, copper, &c, are 

 indeed found to unite in the proportions repeated in these 

 tables with a certain or constant quantity of all other elements, 

 as for example, with 978 bromine, with 157^ iodine, etc. 



On extending the inquiry to other substances, it appears that 

 for each of them, a number may be found which expresses in 

 like manner, the proportion in which that substance unites 

 with 100 parts of oxygen, 201 of sulphur, 442 of chlorine, 

 &c. These numbers constitute the combining proportions, or 

 equivalent quantities of bodies, which are introduced in the 

 tables of the names of the elements at the beginning of this 

 chapter, and which are the quantities understood to be ex- 

 pressed by the chemical symbols of these bodies. Any series 

 of numbers may be chosen for the combining proportions, pro- 

 vided the true relation between them is preserved, as in the 

 second series of numbers given in the same tables, which are 

 all 12j times less than the numbers of the first series. The 

 second series expresses particularly the proportional quantity of 

 each of the elements, which unites with one part of hydrogen, 

 the element, the combining proportion of which is the smallest. 



