through another series of coils surrounded by a jacket of liquid air. An exhaust
pump was used to reduce the pressure in the jacket and allow the air to boil
thereby further cooling the hydrogen in the coils via the Joule-Thompson
effect. Finally, the cold hydrogen was passed through an expansion valve
which caused further cooling by the same effect
11 to produce liquid hydrogen
collected in a vacuum flask. Remaining gaseous hydrogen was returned to the
compressor to be re-circulated.
Apart from the vacuum flasks
12 and the expansion valve which was built by
Brin’s Oxygen Works Horseferry Rd., Westminster, (later the British Oxygen
Company, BOC) the materials and skills were provided locally or ‘in house’.
The apparatus itself was made from brass tubing and blanks easily obtained
from metal dealers in Clerkenwell, London. Making the apparatus required
little more than some skill in soldering and the only accessories required were
the exhaust pump and a motor to drive it. Fortunately, a student had a
blowing pump in his private workshop, and with its valves reversed, it served
as the exhaust pump. The motor was borrowed from the Engineering
department. The apparatus was literally made from ‘odds and ends’, it was
built in just six weeks and cost about £50. The only design difficulty faced
was the problem of connecting the receiving glass vacuum vessel with the
metal body of the liquefier. This was overcome by a compressed rubber ring
whilst the only operational difficulty was caused by the blockage of the
expansion valve and its seizure at such low temperatures. By soldering a cross
bar to the head of the valve, enough ‘purchase’ could be achieved to force the
valve to open, and blockages were cleared by allowing the pressure to rise.
The apparatus was used for the first time on Saturday 30 June 1899. Mr.
Holding and a team of willing senior students prepared the hydrogen and the
liquid air, and after initial cooling with the solid carbon dioxide and the liquid
air, the compressor and exhaust pump were started. When the pressure rose
to 180 atmospheres the expansion valve was opened and liquid hydrogen
collected in the receiving vessel. However, this was short lived as the valve
both seized and blocked. The next day, having soldered the cross bar to the
head of the valve, the experiment was repeated and when the valve blocked
again Travers allowed the pressure to rise, much to Ramsay’s distress who
cried ‘It’ll burst Travers … it’ll burst!’ The valve however cleared and the
apparatus remained intact for the duration of the experiment and indeed for
the next four years being used continually by Travers and his colleagues until
he left the department in 1903.
5
By the time Robert arrived in the chemistry department at UCL the
liquefier had been mounted in a prominent position on the wall outside the
compressor room. For a young man ‘interested in mechanics’ and developing
100
D. Sheppard
pump was used to reduce the pressure in the jacket and allow the air to boil
thereby further cooling the hydrogen in the coils via the Joule-Thompson
effect. Finally, the cold hydrogen was passed through an expansion valve
which caused further cooling by the same effect
11 to produce liquid hydrogen
collected in a vacuum flask. Remaining gaseous hydrogen was returned to the
compressor to be re-circulated.
Apart from the vacuum flasks
12 and the expansion valve which was built by
Brin’s Oxygen Works Horseferry Rd., Westminster, (later the British Oxygen
Company, BOC) the materials and skills were provided locally or ‘in house’.
The apparatus itself was made from brass tubing and blanks easily obtained
from metal dealers in Clerkenwell, London. Making the apparatus required
little more than some skill in soldering and the only accessories required were
the exhaust pump and a motor to drive it. Fortunately, a student had a
blowing pump in his private workshop, and with its valves reversed, it served
as the exhaust pump. The motor was borrowed from the Engineering
department. The apparatus was literally made from ‘odds and ends’, it was
built in just six weeks and cost about £50. The only design difficulty faced
was the problem of connecting the receiving glass vacuum vessel with the
metal body of the liquefier. This was overcome by a compressed rubber ring
whilst the only operational difficulty was caused by the blockage of the
expansion valve and its seizure at such low temperatures. By soldering a cross
bar to the head of the valve, enough ‘purchase’ could be achieved to force the
valve to open, and blockages were cleared by allowing the pressure to rise.
The apparatus was used for the first time on Saturday 30 June 1899. Mr.
Holding and a team of willing senior students prepared the hydrogen and the
liquid air, and after initial cooling with the solid carbon dioxide and the liquid
air, the compressor and exhaust pump were started. When the pressure rose
to 180 atmospheres the expansion valve was opened and liquid hydrogen
collected in the receiving vessel. However, this was short lived as the valve
both seized and blocked. The next day, having soldered the cross bar to the
head of the valve, the experiment was repeated and when the valve blocked
again Travers allowed the pressure to rise, much to Ramsay’s distress who
cried ‘It’ll burst Travers … it’ll burst!’ The valve however cleared and the
apparatus remained intact for the duration of the experiment and indeed for
the next four years being used continually by Travers and his colleagues until
he left the department in 1903.
5
By the time Robert arrived in the chemistry department at UCL the
liquefier had been mounted in a prominent position on the wall outside the
compressor room. For a young man ‘interested in mechanics’ and developing
100
D. Sheppard