real connection between the two, because a bulb’s wattage is a measure of the
input energy and there is no guarantee that all the electrical input energy is
converted to light. However, one cp equals 0.981 cd, which measures luminous intensity in a given direction of a source that emits monochromatic light
of 1/683 W per steradian—a sphere measuring 4p (12.56637) steradians. So,
one cp at 0.981 cd, equals 0.981/683 per steradian or about 0.2 W over the
whole sphere. 700 cp was therefore about 140 W output. Pretty poor really.
4. Hermann Sprengel was a German born chemist who developed the pump
whilst working in London in 1865. Sprengel pumps were not only used by
Crookes, but by Ramsay, Swan and Edison as well. The pump was a critical
component for incandescent light technology removing enough air to allow the
filament to glow for a commercially useful life time. See for example: http://en.
wikipedia.org/wiki/Sprengel_pump.
5. Selling his patent to the AEG (Allgemeine Elektrizitätsgesellschaft) in 1898
reputedly made him one million Reich Marks. Diana Kormos Barkan, Walther
Nernst and the Transition to Modern Physical Science. Cambridge University
Press, 1999, p. 100.
6. Kormos Barkan, op. cit. (note 5), p. 94.
7. Margit Szöllösi-Janze, Fritz Haber 1868–1934: Eine Biographie. C. H. Beck,
Munich, (1998), pp. 185–186.
8. Haber’s royalties were established at about one Pfennig per kg ammonia with
the help of Engler in 1913. There was some discussion of a fixed payment of
7.5% profits which Haber tried to re-instate post-war to protect his income
from erosion by inflation. From Szöllössi-Janze, op. cit. (note 7), pp. 482–483.
9. Thomas Hager, The Alchemy of Air, Three River Press, New York, (2008),
p. 103, and his references.
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D. Sheppard
input energy and there is no guarantee that all the electrical input energy is
converted to light. However, one cp equals 0.981 cd, which measures luminous intensity in a given direction of a source that emits monochromatic light
of 1/683 W per steradian—a sphere measuring 4p (12.56637) steradians. So,
one cp at 0.981 cd, equals 0.981/683 per steradian or about 0.2 W over the
whole sphere. 700 cp was therefore about 140 W output. Pretty poor really.
4. Hermann Sprengel was a German born chemist who developed the pump
whilst working in London in 1865. Sprengel pumps were not only used by
Crookes, but by Ramsay, Swan and Edison as well. The pump was a critical
component for incandescent light technology removing enough air to allow the
filament to glow for a commercially useful life time. See for example: http://en.
wikipedia.org/wiki/Sprengel_pump.
5. Selling his patent to the AEG (Allgemeine Elektrizitätsgesellschaft) in 1898
reputedly made him one million Reich Marks. Diana Kormos Barkan, Walther
Nernst and the Transition to Modern Physical Science. Cambridge University
Press, 1999, p. 100.
6. Kormos Barkan, op. cit. (note 5), p. 94.
7. Margit Szöllösi-Janze, Fritz Haber 1868–1934: Eine Biographie. C. H. Beck,
Munich, (1998), pp. 185–186.
8. Haber’s royalties were established at about one Pfennig per kg ammonia with
the help of Engler in 1913. There was some discussion of a fixed payment of
7.5% profits which Haber tried to re-instate post-war to protect his income
from erosion by inflation. From Szöllössi-Janze, op. cit. (note 7), pp. 482–483.
9. Thomas Hager, The Alchemy of Air, Three River Press, New York, (2008),
p. 103, and his references.
198
D. Sheppard