California Association of Chemistry Teachers
G. Ross Robertson
University of California 10s Angeles 90024
The Laboratory Ringstand Problem And the UCLA solution
1he standard portable ringstand has never been a very satisfactory device for various reasons. For as long as 44 years an intermittent campaign has been in progress a t UCLA to eliminate the ringstand nuisance from five successive chemistry laboratory buildings, and some valuable experience has accumulated. The Fixed Vertical Rod
The first experiment was a flat f a i l u r e t h e use of a vertical rod anchored to the laboratory hench top by a stationary steel flange. This device offers a simply irresistible temptation to the idle visitor to rock the rod hack and forth. About three trials of this experiment loosen the outfit and permanently put it out of commission. The Fixed Horizontol Rod Holder
By the time No. 2 of the "exploding" succession of UCLA chemistry buildings was authorized, we concluded that a clamp or rod holder firmly attached to the student's individual reagent shelf was requisite. After all, the base or table level is not the position where the rigid support of chemical apparatus is needed. This idea is by no means an original Los Angeles concept. The Chemistry Department of Washington State University (Pullman) has long since installed a practical device of this type, as described by Bailar.' The Washington device, however, is not a clamp, hut rather a simple, inexpensive, and fairly rugged means of attaching a vertical rod to a horizontal shelf without mechanism for adjusting the effectivelength of the rod in daily use. It was quickly decided in the Los Angeles laboratory that an adjustable clamp was essential, and samples were prepared of the general style shown in the accompanying three sketches. These were promptly dubbed in the local vernacular as "cast-iron fists." Not all shortcomings were immediately apparent, and it required three decades of practical trial to reveal and eliminate defects in design and materials. The three
Contribution No. 1796 from UCLA Chemistry Department. B A ~ A JOHN R C. JR., in "Laboratory Design," 1st ed., COLEMAN, H. S., editor, Reinhold Publishing Carp., New York, 1951, p. 95.
sketches herewith embody the latest preferences of Los Angeles staff. Shelf Suitable for Adjustable Clamps
Obviously we hastened to rule out the recently popular hench design with no reagent shelf over the working bench top. Instead there should be a stout wooden shelf, preferably of solid maple or birch, about 3 M 0 mm thick. Conventional shelving, made of standard American lumber, rough-sawed 1 in. and then surfaced on both sides, is definitely too light and leads to warping, unsightly angular displacement of rods, etc. In all this it is assumed that the main laboratory table top lies about 0.95 meter from floor level. Care must be taken that horizontal pipes under the shelf do not come closer than 32 nun from the shelf. This admonition will please the plumbing contractor as well as the clamp installer. Research workers, physical as well as organic, insist that clamps of the type cited above must not be mounted on the top of a shelf, where they would interfere with bottles and other bulky ware. This means keeping the shelf top free not only from large obstructious hut also from bolt and screw heads. The clamps are accordingly mounted under the shelves and anchored by elevator bolts. The elevator bolt has a wide flat head, flush with the shelf top as seen in the "TOP" and ''SDE" sketches herewith. It is readily available in American wholesale hardware trade. Laboratory maintenance personnel use hex automobile wrenches to preserve tight adjustment. Material for Clamp Body ond Screw Fastener
In an institution with many inexperienced but quite able-bodied freshmen, it is astonishing the amount of punishment such a clamp must face as the years pass. Diecast aluminum alloys, "pot-metal" and other nonferrous material, extremely popular today in the lahoratory-clamp market, are wholly unsatisfactory for the main shelf clamp. Special high-strength cast iron of the "Meehanite" type or equivalent is necessary. A polymeric corrosion-resistant coating completes the job of manufacture. The manufacturing contractor should take particular pains to see that the top surface of the Volume 42, Number 7, July 1965
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clamp is exactly perpendicular to the mounted rod in all specimens of the casting. A conventional prescription for screw fastener would be the standard thumb screw with paddle handle, used widely in present-day laboratory fittings. Twenty years of mediocre service convinced us that neither the thumb screw nor its twin sister, the cast-brass wing screw, is satisfactory. When an inexperienced student finds that the wing screw does not afford an adequate grip on the ringstand rod, he gets pliers or a wrench. This "upsets" the thread on the brass fastener, to use the machinist's vernacular. That is, the threaded portion of the fastener is shortened, accordion-fashion. Following such mechanical abuse, it becomes impossible to back out the screw so that the main rod may be withdrawn sidewise, as often desirable in laboratory use. I n the device presented here we follow in one sense the experience of years in lathe and milling machine design. Wing and thumb screws are replaced by the right-angle screw, which is convenient for simple hand operation. On the other hand, it is so awkward to handle with pliers or wrench that the laboratory worker is unlikely to look for such auxiliary tools. Hazard of mechanical injury is thus reduced. Stainless steel is recommended for the right-angle screw, but this specification is more in the interest of resistance to thread upsetting rather than corrosion. The stainless alloys have a high rating in tensile and compression strength. Many workers assume that such a "stainless" screw is corrosion-proof, but the present writer advises that both body of clamp and unthreaded portion of the fastener be lacquered. American s1,andardvlsin. (about 8 mm) cylindrical rod is suitable for such screws. Ringstand Rods
The American standard '/2-in., or about 12.7 mm cold-drawn smooth steel rod is recommended. Here again it is customary to assume that such a rod, of stainless steel, would be entirely satisfactoly, but such is not thoroughly L'stainless"in laboratory atmospheres. An economical substitute used in our laboratory for several years consists of cold-drawn, open-hearth
smooth steel rod cut into desired lengths and then dipgalvanized. Iron rods electroplated with zinc, and commercial "galvanized" rod cut after being coated, are not acceptable. The presence in an elementary laboratory of zinc-coated rods, supposedly vulnerable to the acids used so much in such a room, offers no important disadvantage. One is reminded of the fact that a galvanized iron roof is more resistant to the weather than uncoated iron, a metal of lower electrical reduction potential. Rods about 60 em long are suitable for freshman laboratories, and about 90 cm for more advanced work When introduced to this equipment, students promptly elevate the vertical rods a few cm from table level. Such elevation gives freedom of adjustment as assemblies of apparatus approach completion. It also facilitates good housekeeping a t cleanup time. If the outfit is heavy, the whole assembly is readily lowered in one move to rest solidly on the laboratory bench. Fluid rubber preparations are available in the market to suit users who may fear damage to certain kinds of bench top in rapid lowering of rods. The lower end of the rod is coated with the rubber. At UCLA, two rods spaced about 33 cm apart are provided a t each freshman student station. More advanced laboratories with longer stations have the two as above, and a third as far as possible from the 33-cm pair. The 33-cm interval serves well as a good average spacing for standard distillation outfits. Obviously small replicas of the increasingly popular "reaction rack'' or "vacuum rack" are readily assembled over a laboratory bench equipped with clamps as described above. I t is well in drawing up a contract to provide a few dozen spare clamps for more elaborate setups. The author wishes to thank Mr. Kenneth G. Hookanson, Director of Research and Development, H. M. Harper Co., 8200 Lehigh Avenue, Morton Grove, Ill., for important advice on corrosion-resistant screw fasteners; also local UCLA staff members with good ideas on mechanical design of the clamps, including Professor Morris Asimow and Messrs. Russell W. Bemis and Frank Schuster.
Summer Conferences
400
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Seventh CACT
Twenty-Seventh NEACT
Asilomar: Auguat 1 5 2 1 Information: Write Mrs.W. A. Craig, 1199 Laurel Street, Pasadena, California, 91103.
Simmons College; Auguat 1G20 Information: Write Dr.PhyUia Brauner, Simmons College, Boston, Massachubetts.
Journal of Chemical Education
