410 COMPOUNDS OF HYDROGEN, 



pungent odour, familiar in spirits of hartshorn. It is composed 

 of 2 volumes of nitrogen and 6 of hydrogen, condensed into 4 

 vols., which form the combining measure of this gas. Ammonia 

 is resolved into its constituent gases, in these proportions, when 

 transmitted through an ignited porcelain tube containing iron or 

 copper wire, while the metal, at the same time, becomes brittle, 

 and is supposed by Despretz to absorb nitrogen, although this 

 is doubtful. By a pressure of 6.5 atmospheres, at 50, it is con- 

 densed into a transparent colourless liquid, of which the sp. gr. 

 is about 0.76. Ammoniacal gas is inflammable in air in a low 

 degree, burning in contact with the flame of a taper. A mix- 

 ture of this gas with an equal volume of nitrous oxide may be 

 detonated by the electric spark, and affords water and nitrogen. 

 Water is capable of dissolving several hundred times its volume 

 of ammoniacal gas, and the solution is always specifically lighter, 

 and has a lower boiling point than pure water. According to 

 the observations of Davy, solutions of sp. gr. 0.872, 0.9054 and 

 0.9692 contain respectively 32.5, 25.37 and 9.5 per cent of 

 ammonia. Ammoniacal gas is also largely soluble in alcohol. 



Solution of ammonia has an acrid alkaline taste, and pro- 

 duces blisters on the tongue and skin. When cooled 

 slowly to 40, it crystallizes in long needles of a silky lustre. 

 The solution has a temporary action upon turmeric paper, which 

 it causes to be brown while humid ; it also restores the blue 

 colour of litmus reddened by an acid, changes the blue colour 

 of the infusion of red cabbage into green, and neutralizes the 

 strongest acids, properties which it possesses in common with 

 the fixed alkalies. When ammonia is free, it may always be 

 detected by its odour, by forming dense, white fumes with 

 hydrochloric acid, and by forming a deep blue solution with 

 salts of copper. 



Ammonia, in solution, is decomposed by chlorine, with the evo- 

 lution of nitrogen gas and formation of hydrochlorate of ammonia ; 

 when ammonia and chlorine, both in the state of gas, are mixed 

 together, the action that ensues is attended with flame. Dry 

 iodine absorbs ammoniacal gas, and forms a brown viscous liquid 

 (page 388), which water decomposes, dissolving out hydriodate 

 of ammonia, and leaving a black powder, which is the explosive 

 iodide of nitrogen. 



The consideration of ammonia, as a compound of amidogen 

 and hydrogen, was involved in the explanation given by Dumas 



