156 AMMONIUM COMPOUNDS.
AMMONIUM COMPOUNDS AND SUBSTITUTED AMMONIUM
COMPOUNDS.
- Dissociation of Ammonium Chloride.
The fact that the vapor density determination of ammonium chloride
shows the molecular weight to be but one-half the formula weight, leads to
the conclusion that the number of molecules is doubled by the dissociation of
the substance into ammonia and hydrogen chloride. If the compound is
volatilized into an atmosphere either of ammonia or of hydrogen chloride, the
dissociation is driven back in accordance with the mass-action law — this
phenomenon being especially pronounced when working at lower temper-
atures and under reduced pressure. In the complete absence of water the
dissociation fails to take place, thus showing in a remarkable manner the
catalytic effect of traces of moisture.
The dissociation of ammonium chloride may be demonstrated qualita-
tively, by taking advantage of the greater velocity at which the lighter
ammonia diffuses as compared with the heavier hydrogen chloride; the
products of diffusion may be most conveniently separated by the use of a
diaphragm.
Fasten a piece of combustion tubing, 20 cm. long, in a hori-
zontal position. Insert a loose plug of asbestos at the middle of
the tube, and place about a gram of ammonium chloride on one
side of the plug. Heat the asbestos diaphragm and the ammonium
chloride by means of a wide burner so that a slow sublimation
takes place and the entire tube becomes filled with the vapors.
After a few minutes test the gases at both ends of the tube with
moist litmus paper. An acid reaction is shown on the side of
the asbestos plug on which the solid salt was placed, while on the
other side an alkaline reaction is obtained.
- Hydroxylamine Sulphate, [NH 2 OH.H] 2 SO 4.
Sodium nitrite and sodium bisulphite react together in cold aqueous solu-
tion, at first molecule for molecule, forming nitrososulphonate of sodium:
ONjONaTHiSOjNa = NaOH + ON-SO 3 Na.Then, by the immediate taking up of a second molecule of sodium bisul-
phite, the stable sodium salt of hydroxylaminedisulphonic acid results:
ON-SO 3 Na + NaHSO 3 = HO-N(SO 3 Na) 2.
If the solution is warm a third molecule of sodium bisulphite reacts and
nitrilo-sulphonate of sodium is formed.
When heated above 100° with water the sodium salt of hydroxylaminedi-
sulphonic acid is hydrolyzed into hydroxylamine and sodium bisulphate:
HON(SO 3 Na), + 2 H 2 O = H0NH 2 + 2 NaHSO 4 ,