PROCEEDINGS 
OF THE 
ROYAL SOCIETY OF EDINBURGH. 
YOL. XXXIII. 
1912-13. 
I. — On a Method of determining Vapour Densities a,t High 
Temperatures, and on a new form of Quartz Manometer. By 
G. E. Gibson, B.Sc., Ph.D. (Carnegie Fellow, 1912). Communicated 
by Professor John Gibson. 
(MS. received November 6, 1912. Read January 6, 1913.) 
All methods of vapour density determination hitherto in use, in which 
quartz or glass manometers are employed, suffer from the disadvantage 
that the highest temperature attainable is about 7 50° C. 
It is, however, possible to overcome this difficulty whenever the 
substance under investigation has a considerable vapour pressure below 
750° C * 
If we heat the bulb (volume V) which contains the main bulk of the 
vapour in one furnace whose temperature T may be varied at will, and 
the manometer (volume v) in a separate furnace at a constant tempera- 
ture t (less than 750° C.), we can calculate the vapour density A, relative 
to hydrogen at the temperature T, by the formula : 
m RT vTg 
[x pv Y t 
(i) 
Here R is the gas constant, m is the total weight of substance in the 
apparatus, p. is the molecular weight of hydrogen (2 '01 6), p is the 
measured pressure, and S is the vapour density of the substance at the 
temperature t. 
* Starck and Bodenstein ( Zeit.f . EleHrochem., vol. xvi. p. 161, 1910) describe a method 
similar to mine. I was unaware of the existence of this paper until mine was ready for 
publication. 
VOL. XXXIII. 
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