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How to Make/Modify and Use an Alcohol Lamp
by  John Gustav Delly, Scientific Advisor, Hooke College of Applied Sciences, Westmont, IL

10/29/2007 (updated 1/15/2008)1 | 2 | 3 | 4 | NEXT>> 


The ubiquitous alcohol lamp, or “spirit lamp”, seen being used to heat the contents of the retorts in this delightful engraving from the frontispiece of Worthington Hooker’s First Book in Chemistry for the Use of Schools and Families (Harper & Brothers, New York, 1862), is one of the oldest pieces of laboratory apparatus.  The earliest versions, burning oil, and used in conjunction with the blowpipe, were employed by goldsmiths in ancient Egypt for making jewelry.

 

Alcohol lamps have been present throughout the history of chemistry.  There is even one included in virtually every child’s chemistry set, or, if not included, directions are supplied for constructing one.  In spite of its long history, most alcohol lamps are not used properly, resulting, most often, in flooding of the fuel, leading to burning corks and other fire hazards, as well as corrosion of the metal parts.  Additionally, most commercially available alcohol lamps need to be modified for use in the microscopy laboratory, where, in addition to general heating requirements, the flame needs to be made smaller, in keeping with the scale of microchemical glassware and technique.  Amongst the considerations in making and/or modifying an alcohol lamp for microscopical use are:  (1) size, capacity, and form of the fuel container (faceted/unfaceted, globe-shaped, squat; glass, metal); (2) nature of the fuel and its temperature when burned; (3) fuels and the visibility of their flames; (4) caps:  ground-glass, steel, aluminum, brass; glass hood, metal hood; (5) wick material:  woven cotton, cotton string, glass fiber; (6) wick size and shape; (7) wick’s feed mechanism; (8) wick’s feed-through support:  glass, brass, copper, steel, ceramic; (9) portability; (10) provision for pressure equalization.

 

 

Common Faults with Alcohol Lamps and Their Use

 

The three most common faults with alcohol lamps and their use in the microscopy laboratory are (1) overfilling (2) failure to provide for pressure equalization, and (3) use of too large a wick, especially one that is also not kept trimmed.  Of these, the most important is the failure to provide for pressure equalization.  In totally sealed systems, such as those illustrated in Figure 1, changes in temperature and atmospheric pressure will cause the alcohol lamp to act like a liquid barometer, forcing the alcohol up and out of the wick; even the heat from the hand will cause the alcohol to be driven out, especially so with an overfilled lamp.  Removing the ground-glass stopper, and lighting the lamp, will ignite the excess alcohol, creating a fire hazard.  Well-designed alcohol lamps have a tiny hole drilled through the cap or cork to act as a “breather tube” or vent to maintain equal pressure inside of, and outside of the fuel reservoir.

 

Overfilling of the lamp with fuel is an easily corrected mistake.  If the lamp reservoir is only filled about half way, or somewhat more, there will be less likelihood of sloshing alcohol up the wick, wick support, or out of the pressure equalization vent when handling.

 

For microscopical use, the wicks, as normally supplied, are much too large.  As smaller wicks do not seem to be commercially supplied with these lamps, the average lamp needs to be modified.  Inserting a short length of narrow metal tubing with an inside diameter about the size of cotton wrapping string is a common expedient, if not the most pleasing aesthetically; such a modification is shown in the case of the alcohol lamp on the left in Figure 1.  Both of the lamps in Figure 1 lack a vent for pressure equalization.

 

Let’s look at some examples of alcohol lamps, and then comment on them.


10/29/2007 (updated 1/15/2008)1 | 2 | 3 | 4 | NEXT>>