12 ANIMAL CHEMISTRY LECTURE I. 



three times as much hydrogen, and from the steam twice as 

 much hydrogen, as can be got from the hydrochloric acid ; 

 whereas the amount of nitrogen we can extract from the ammonia 

 is exactly equal in bulk to the amount of oxygen we can extract 

 from the steam, and to the amount of chlorine, and, consequently, 

 of hydrogen, we can extract from the hydrochloric acid. It is 

 also a matter of fact that taking equal volumes of hydrogen, 

 chlorine, oxygen, and nitrogen, the weights of these equal 

 volumes are in the proportion of 



i : 35'5 : 16 : 14 

 as shown more fully in the table before you. 



Specific gravities or weights Molecules or weights of 



of one volume two volumes 



Hi H, 2 



Cl 35-5 Cl, 71 



16 0, 32 



N 14 N a 28 



IHCI 18-25 HCI 36-5 



|H 3 O 9 H a O 1 8 



IH 3 N 8-5 H 3 N 17 



{H 4 C 8 H 4 C 1 6 



(i I .) Now we come to a matter of interpretation. From these, 

 in addition to many other considerations, we accord to hydrogen, 

 chlorine, oxygen, and nitrogen the atomic weights i, 35*5, 16, 

 and 14, and we express the comparable molecules of hydrochloric 

 acid, water, and ammonia by the formulae HCI, H 2 O, and H 3 N 

 respectively, each of which represents the same gaseous bulk, or 

 2-volumes of its particular compound. This formula for water 

 is warranted by a host of considerations. It may suffice here to 

 remark that in composition, condensation, and properties, water 

 H 2 O, is strictly intermediate between the acid monhydride of 

 chlorine HCI, and the alkaline trihydride of nitrogen H 3 N. 

 Further, what is true of hydrochloric acid is also true of hydro- 

 fluoric acid, hydrobromic acid, and hydriodic acid. From 

 2-volumes of each of these gases we are able to extract a single 

 volume of hydrogen; while from equal bulks of sulphuretted, 



