TAKING THE DENSITY OF VAPOUR OF VOLATILE LIQUIDS. 465 
expansion-coefficient not differing widely from -00366. No exception has yet 
been established ; for, in those cases of which sulphur is the representative, it 
is at least probable that truly polymeric bodies exist. 
Another illustration of the vapour-density methods above described consists 
in an inquiry into the existence of hydrated oxide of ammonium. 
Can hydrated oxide of ammonium exist at 100° C., and in the gaseous state ? 
To solve the problem, a quantity of dry ammonia was measured over mercury, 
then a small portion of water, which had been accurately weighed in a thin glass 
bulb, was introduced into the ammonia. The whole was then heated up to 
100° C., and the volume of mixed gas and aqueous vapour noted. It will be 
obvious that the formation of hydrated oxide of ammonia would be indicated by 
contraction. If, on the other hand, the NH, and aqueous vapour, when mixed, 
had the same volume as when separate, no hydrated oxide of ammonium had 
- been produced. 
The following are the details of the experiment :— 
Corrected Vol. 




Observed Vol. Temperature Pressure in in Cubic Cent. 
in Cubic Cent. Centigrade. Millimeters. at 0° C. and 
760 m. m. 
Vol. of dry NH,, . : 34:19 12-5° 558°08 24-008 
Vol. of NH, + water, . 107-32 102°C. 709°66 72-973 
‘0402 orm. of water taken. 
But -0402 grm. of water, when converted into vapour, measures 49-95 cub. 
centimeters at 0° C. and 760 m.m. The difference between the readings before 
and after the addition of that amount of water is 48-965 cub. cent. Therefore, at 
100° C., ammonia and aqueous vapour can exist side by side without suffering 
any considerable contraction. 
VOL. XXII. PART III. 6D 
