IO ANIMAL CHEMISTRY LECTURE I. 



litres of steam is identical with the conjoint weight of one litre 

 of oxygen and of two litres of hydrogen ; so that while from 

 two litres of hydrochloric acid gas we can extract only one litre 

 of hydrogen in addition to the one litre of chlorine, from the 

 same bulk of steam or gaseous water we can extract two litres of 

 hydrogen in addition to the one litre of oxygen. In the experi- 

 ment taking place on the table of the electrolytic decomposition 

 of water, you see we have roughly, for the single volume of 

 oxygen, a double volume of hydrogen ; and by performing the 

 experiment with certain precautions, we should obtain exactly 

 twice as much hydrogen in the one tube as we obtained oxygen 

 in the other. 



(9.) Let us now direct our attention to the third typical 

 hydride, namely, hydride of nitrogen or ammonia. The com- 

 bination of hydrogen with nitrogen to form ammonia can be 

 effected by indirect methods only ; but it may be shown by a 

 variety of processes, with which I will not trouble you, that 

 these two gases always unite with each other in the ratio of one 

 volume of nitrogen to three volumes of hydrogen. But nitrogen 

 is found to be exactly 14 times heavier than hydrogen; and, 

 accordingly, taking the specific gravity of hydrogen as unity, the 

 specific gravity of nitrogen will be 14; or, calling the weight of 

 a litre of hydrogen I crith, the weight of a litre of nitrogen will 

 be 14 criths. Hence we have in ammonia three volumes of 

 hydrogen combined with one volume of nitrogen, or 3 parts by 

 weight of hydrogen combined with 14 parts by weight of 

 nitrogen, thus : 



Ammonia 



Further, when one volume of nitrogen combines with three 

 volumes of hydrogen to form ammonia, the four volumes become 

 condensed into exactly two volumes. I cannot show you this 

 conversion of four volumes of mixed nitrogen and hydrogen into 

 two volumes of combined nitrogen and hydrogen, but the reverse 

 experiment is of very easy performance. Thus, if we submit 



