243 



T 



CHAPTER VI 



THE COMPOUNDS OF NITROGEN WITH HYDROGEN AND OXYGEN 



IN the last chapter we saw that nitrogen does not immediately combine 

 with hydrogen, but that a mixture of these gases in the presence of 

 hydrochloric acid gas, HC1, forms ammonium chloride, NH 4 C1, on the 

 passage of a series of electric 

 sparks. 1 In ammonium chlo- 

 ride, HC1 is combined with 

 NH :i , consequently N" with 

 H 3 forms ammonia. 2 Almost 

 all the nitrogenous sub- 

 stances of i)lants and ani- 

 mals evolve ammonia when 

 heated with an alkali. But 

 even without the presence 

 of an alkali the majority of 



nitrogenous Substances, when FiG.J2.-The dry distillation of bones on a large scale. 



decomposed or heated with a 



limited supply of air, evolve 



their nitrogen, if not entirely, 



at all events partially, in 



the form of ammonia. Thus, 



when animal substances such 



as skins, bones, flesh, hair, horns, ifcc., are heated without access 



of air in iron retorts or, as it is termed, are subjected to dry distil- 



1 The ammonia in the air, water, and soil proceeds from the decomposition of the 

 nitrogenous substances of plants and animals, and also probably from the reduction of 

 nitrates. Ammonia is always formed in the rusting of iron. Its formation in this case 

 depends in all probability on the decomposition of water, and on the action of the hydro- 

 gen at the moment of its evolution on the nitric acid contained in the air (Cloez), or on 

 the formation of ammonium nitrite, which takes place under many circumstances. The 

 evolution of vapours of ammonia compounds is sometimes observed in the vicinity of 

 volcanoes. 



2 If a silent discharge (as in the ozonisation of oxygen), or a series of electric 

 sparks (for instance, in a eudiometer), be passed through ammonia gas, it is decomposed 



R2 



The bones are heated in the vertical cylinders C (about 

 li metres high and 30 centimetres in diameter). The 

 products of distillation pass through the tubes T, into 

 the condenser B, and receiver F. When the distillation 

 is completed the trap H is opened, and the burnt bones 

 are loaded into trucks V. The roof M is then opened, 

 and a fresh quantity of bones charged into the cylinders. 

 The ammonia water is preserved, and goes to the pre- 

 paration of ammouiacal salts, as described in the follow- 

 ing drawing. 



