inflation fighter/ The response of the readers to this column has been verv gratifying. A number of people have taken the time to prepare notes on their inflation fighter ideas. We h o ~ that e there will he no slackenmg of the outstandmg articles submitted. In this column we will look at a revision by Charles R. Eisnor of a low-cost DH meter similar to the one described in an earlier CHEM. EDUC.58, 281 (1981)l and two methods article [i. proposed by Victor Rhodes and Susan Nurrenbern for saving on the dispensing of chemicals. But before getting to these interesting t o ~ i c s I. would like to nass on a few short comments received f&m concerned readers. Mr. Douglas Firebauah, a chemistrv instructor in F r e e ~ o r tIllinois. . raised an objection to my s&estion of substituting copper solutions for silver nitrate in the dis~lacementexoeriment IJ. CHEM. EDUC.57,892 (1980)l. ~ e w ajustifiabh s worried that some high school students might form the wrong conclusion about the mass relationships. My example was used only as a demonstration on how we as chemistry teachers could rethink traditional experiments in order tdcut the cost of scientific education. The saving of money is never worth the price of miseducation! Anne Sherren of North Central College in Naperville, Illinois, sent in one cost fighter that she was happy to share with everyone: Do look all gifts over carefully before you accept them. Many are pure gold, but others can be expensive junk. If the equipment is old and not functioning, remember that repairs on that type of apparatus is astronomically expensive-assuming that parts are available. ~
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pH Meter Revisions
Since the "pH Meter Proiect" was ~ublishedin Acadian a common (easy-to-find) 0-1 mA DC panel meter ( ~ a d i o Shack JtRS2701-1752). In t h k case
Set up, the calibration procedures are the same as previously published, except that the voltage - between Din 2 and 3 is not 0 V. Set the "adjust" and "temp" knobs at center and adjust RV2 (and if necessary, RV1) until the meter reads pH 7 (with electrode dipped in buffer of pH 7). If the meter pins or the meter aenerallv does not behave. rotate RV4 to limit the then dipping theklectrode in'the buffer of pH 10. The needle should move toward DH 10. If i t Dins. rotate RV4 sliehtlv to bring it back to pH i0. Then cceck pH 7 again. ~'ing'the needle to pH 7 with the "adjust" and "temp" controls. The "temp" control is very sensitive, so only a small adjustment should be necessary. Continue the above adjustments until the meter reads exactly pH 7 and pH 10 without moving the controls. While the Journal of Chemical Education
Topeka.Kansas66621
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Charles R. Eisnor Acadia University Woltville. NS. Canada BOP 1x0
240
ed~tedby SHELDON H COHEN Washburn Unwersny
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10 rr disposable p i p e t
Methods and details of how you can save money by building your own equipment are outlined in this feature. If you have made something which is particularly useful or money saving, please share it with our readers. calibration takes a lot of trial and error, i t is necessary. There is no way around this. Once pH 7 and pH 10 can be read exactly, attempt pH 4. There should be no problem here. If there is, simply recalibrate using the buffers of pH 4 and pH 10. When these read exactly, p H 7 should read perfectly when checked. If the electrode is old or has not been well taken care of, there will be a response problem, and the meter should be calibrated only for use in short ranges (e.g., pH 4 to pH 7 and pH 7 t o pH 10). The modifications are Replace R3,15 K with 2.2 K. Replace Rs, 4.7 K with wire link. These modifications apply only for use with 0-1 mA meter. For use with a 50-0-50 mA meter, the schematic diagram remains unchanged except that Rg (4.7 K) may be increased to limit current if necessary.
' Condon, K., Eisnor, C. R., Acadian Letters, 3 141, 80.
Revisions made 02-15-1981 pH meter circuit boards, drilled, tinned. and readv for cornDonent mountq are ava.laole at $2 50 (Canadian, p "s $0'50 pasla& erc. Send remillance lo' Acad an -eners cro Cnem sby DepaRment. Acadia .,nlvers ty. Woltv he. N S.. Canaoa BOP 1x0
Savings in Dispensing of Chemicals Victor C. Rhodes Susan C. Nurrenbern Unlverslty of Wlscons~n-Stout Menomonme, WI 54751
the quantities of materials required and when reagents become contaminated. This waste of reagents means a waste of money from tight department budgets. The chemistry dewartment at the Universitv of Wisconsin-Stout has managed . to cut the amount of wasted reagents in two ways. The two systems have been used in our general laboratory courses for several years with a considerable saving of money spent for reagent replacement. We have observed a 50 percent decrease in volume of liquids and solutions used for the laboratories during the time the pipetting device has been in use. Solids are placed in small (4.02) plastic specimen containers for student use. The specimen containers we use are widemouthed containers. We find that this allows easv access to the solid and results in less spilling of reagents at the reagent table. If contamination occurs.. onlv a small amount of reaeent " must be discarded. Liquids and solutions are dispensed using a pipetting device designed by the staff at UW-Stout and tested by the students. The device is simwle and inexwensive to make. Students take only the amoint of reagent called for in the experiment directions with no need to transfer it to an extra container. This eliminates the waste caused by students' overestimation of required quantities of liquids and solutions. With a pipetting device for each reagent, we have found that there is no contamination of one solution with another. The pipetting device can he adapted to fit any size reagent hottle. Reagent hottles may be obtained from various sources. Discarded glass IV hottles are used extensively at UW-Stout. One-quart cooking oil bottles are also satisfactory for reagent
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hottles. A bottle with a volume much greater than 11seems to he unwieldy with this pipetting device. Constructing an Inexpensive Pipetting Device
10 ce disposable plpet, glass or polystyrene 1hollow polyethylene stopper, size 6 or 7 Tygon" tubing
The use of plastic materials in the construction of this device is preferred because there is less breakage by students when using the pipets. However, polystyrene will dissolve in some liquids and a glass pipet would be appropriate. Punch a hole through the bottom of a hollow polyethylene stopper of appropriate size with a cork borer. A size 7 stopper serves most uurnoses. If necessav. cut a 10 cc disnosahle ninet to a length siiglky longer than t h e reagent bottle. ~ u s&is i 10 cc pipet through the hole in the stopper so that the stopper fits over the mouth of the reagent hottle. Be sure that the tip of the pipet does not touch the hottom of the reagent bottle. The p&t must fit into the stopper very tightly. ~ i n n e cat 10 cc graduated polypropylene syringe to the top of the pipet by using a tight-fitting, short piece of Tygona tubing (see
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plunger. The estimated cost of construction is $0.60 each at 1981-82 catalog list prices.
Volume 59
Number 3
March 1982
241
