IMMERSION WELL REACTORS

A variety of Immersion Well Photochemical Reactors are available for the synthetic photochemist engaged in synthesis employing halogenation, exidation, or degradation methods. The reactors are designed to be efficient and include provision for irradiation by low or medium pressure mercury lamps. Double-walled immersion wells (in quartz or borosilicate glass) permit water cooling of lamps or filtering of excitation radiation. Various reaction flasks enable irradiations to be conducted under anaerobic conditions at low or constant temperature.

Low pressure mercury lamps emit over 90% of their energy at 254nm providing a useful source of ultra-violet radiation for photo reactions. Medium pressure mercury lamps have much more intense arcs and radiate predominantly 365-366nm light with smaller amounts in the ultra-violet region at 265, 297, 303 and 313 nm as well as significant amounts in the visible region at 404-408, 546 and 577-579nm. The choice of lamp power and lamp is determined to some extent by the nature of the photoreaction and volume of reactant solution.

Nominal Wattage	Diameter in mm	Lamp Model	Power Supply Model
6	14	MVL 1	MVL 11
12	26	MVL 2	MVL 21

Nominal Wattage	Diameter in mm	Lamp Model	Power Supply Model
125	20	MVL 3	MVL 31
400	22	MVL 4	MVL 41

Arc sources possess negative voltage-current characteristics, i.e. the voltage drop across the lamp decreases as the current through the lamp increases and conventional low-impedance power supplies cannot be used. Lamps must be operated from reactive type supplies having a large resistance or inductance in series to provide extra power to initiate the arc and reduced power for continuous operation.

These are double-walled wells, made in Quartz or Borosilicate Glass, which house the lamp. Inlet and outlet tubes provide for air or water cooling. A small diameter inlet tube extends to the bottom of the annular space to allow coolant flow from the bottom of the well upwards. A 2-3mm spacing between the walls allows filtering of certain wavelengths (with liquids, e.g.cobalt, nickel or copper sulphate solutions or with gases, e.g.chlorine) to reduce secondary photochemical reactions of products. Note that borosilicate glass does not transmit 254nm radiation.

Overall Length (mm)	Outside Diameter (mm)	Joint	Quartz Well	Borosilicate Well
265	38	45/50	QW1	BW1
390	64	70/60	QW2	BW2

Two types of outer reaction flasks are available. All are made of borosilicate glass and are fitted with one central ground socket (to take an immersion-well) and other smaller sockets for a reflux condenser or dropping funnel, sampling port etc. Flasks may be supported by conventional laboratory stands and clamps.

Cylindrical flask with flattened bottom for magnetic stirrer bar. Provided with one angle socket and one vertical socket. (PTFE tubing for gaseous agitation may be fed through the socket). Suitable for low/constant temperature irradiation.

As standard flask with additional sintered glass disc (dedium porosity) fitted to bottom of flask to permit gas agitation and allow the reaction mixture to be kept under an inert or reactive atmosphere. A glass PTFE stopcock is attached.

Reactant Capacity Nominal (mm)	Length (mm)	Joint	Flask Type		Model
			A Std	B Gas Inlet
150	215	45/40	*		A/150
200	310	70/60	*		A/250
150	315	45/40		*	B/150
200	400	70/60		*	B/200
400	400	70/60		*	B/400

A double surface reflux condenser, prevents `creep' and loss of vapour when low boiling point liquids are used. Will fit all types of reaction flasks. Model RC1.

The following table describes the various Immersion Well Reactors and which are supplied complete with Reflux Condenser.

Model	IWQ1	IWB1	IWQ2	IWB2
Lamp/Power Supply	6 W	125 W	12 W	400 W
Immersion Well	QW1	BW1	QW2	BW2
Reaction Flask	B/150	B/150	B/200	B/200

Note: Full details of liquid cut-off solutions are supplied with the instruction manual.