dlltd bv 1 WALTER A. WOLF Colgde Uniwnily Hemllton. New Yodl

A Good lnexpensive Table for Analytical Balances

Charles G. Moseley The Ohio State Uniuersity-Lima Campus Lima, Ohio 45804

Our school recently faced the problem of providing good tables for analytical balances used by our first-year chemistry students. A limited equipment budget and the high cost of commercial balance tables ($200-250 each) precluded their acquisition.

Investigation showed that excellent balance tahles can be constructed very inexpensively from readily available concrete products. Each table consists of a top working surface (2 ft X 3 ft X %in. precast concrete slab) supported by two pedestals (each of four 8 X 8 X 16-in. concrete blocks). All material was given one prime coat and one top coat of water base paint to improve appearance. The balance operator sits on a 18lh-in. high stool. As shown below, the tables compare favorably to commercial balance tables1.

Commercial Commercial Our Marble Concrete Concrete

Dimensions (in.) I hXwXd) 3 1 X 3 5 X 2 4 3 1 X 3 6 X 2 4 32VrX36X24

we~gnt 750 lbr. 650 lbs; 400 IDS. 510 lbs. Cost $238 8224: 8191 $11.50

If required, the weight of the tables could be increased by simply filling the boles in the concrete blocks with concrete, sand, or other massive material; however, this was not found to be necessary for satisfactory balance performance. In ad- dition, balance performance is also satisfactory on a row of tables constructed of the same material hut using shared in- ternal pedestals (i.e., each internal stack of four blocks sup- porting ends of two slab tops). Cost and labor (but also weight) are obviously even lower for this shared pedestal type of table.

'This data was taken from the 1976 edition of tke Scientific Products Catalogue.

An lnexpensive Safety Pipet for Reagents

Thomas Rees Phillips Academy Andover, Massachusetts 01810

Various designs of rubber bulbs are used for pipetting liq- uids safely. We have designed a simple, safe device which is more convenient and less expensive than the rubber bulb. This device can be used with all liquids that are compatible with the container.

A polyethylene washing bottle is fitted with a one-hole ~. . rubber stopper through which u pipet has heen inserted. The tipof the pipet .should reach nearly ro the bottom ofthe bottle. When the liquid is being stored, the open end of the pipct is rovered with a ruhber l~ulb from a medicine dropper. Durinp. operation, the medicine dropper bulb is remo;ed, and the bottle is squeezed until the liquid rises above the mark on the pipet. The open end of the pipet is covered with the finger of one hand, while the rubber stopper is loosened from the bottle with the other hand in order to equalize the air pressure. The liquid in the pipet is drained to the top mark while the pipet tip is still within the bottle. The filled pipet is then ready for use in the usual manner. The rubber stopper remains attached to the pipet during the entire pipetting operation.

Skits for General Chemistry

Rnbin Battino Wright State University Dayton, Ohio 45431

We have prepared skits on a variety of subjects, which we are using in general chemistry courses as a change of pace from lecturing. The skits are best performed by the lecturer and teaching assistants since it takes some skill to act and project them to a large audience. Students are told that hissing, booing, laughing and other reactions are appropriate-since this is a change of pace many students need permission to react. Many of the skits are deliberately "corny" and "hammy," but also contain didactic content. They are nrostly meant for fun. The titles of the ones we have prepared are: "The Student-Teacher Contract"; "It's a Gas, Man"; "Simply Pure Damn Foolishness"; "Corn is an sp2 Hybrid"; "How Can You Balance an Equation?"; But, is it like Relevant, Man?-A Morning Farrago"; and "Thermogoddammits." Upon request we will be pleased to send you a package containing all of these skits. You are free to use them as you wish. (To cover the cost of reproduction, handling, and mailing, a contribution of $1.00 would be appreciated.)

Permanent Models for Determining Absolute

Configurations

Charles J. Thoman, S.J. University of Scranton Scranton, Penmyluania 18510

The study of stereochemistry today is not complete without instruction in the use of the Cahn-Ingold-Prelog procedure for expressing absolute configurations. Typically, the in- structor will draw a Fischer projection formula on the board

502 / Journal of Chemical Education