pH meters
1
mnething new from the pwt Edited by: JOSEPH S. SCHMUCKLER Chairman of Science Education Temple University 345 Riner Hall Philadelphia. PA 19122 Homemade Lab Equipment In this installment of "Something New From the Past," I am in- cluding articles on simple, inexpensive deviceslapparatus that can be constructed in the lab, inexpensive equipment that people such as you have improvised and reported in the journals. Most of the ar- ticles reviewed here are short. Some of the ingenious ideas are even inspirational. I hope that you will share your improvisationswith your fellow readers by sending them to the editor of our feature, "Inventory Control:" "An Improved Gas Generator for Elementary Chemistry," G. W. Thiessen and H. Hall, J. CHEM. EDUC., 38,19 (January 1961). This is a small-scale gas generator, easy to cnnstruct, efficient, and as flexible as a Kipp's generator. "It provides elf-controlled evolution of gas from solid and liquid reagents,with reservegasstorage capac- itv." Waste oroducts are easilv siohaned off. The eenerator is ca~able . . - of almost continuous operation. An easily understandable diagram is provided for constructing the apparatus. "A Test Tube Automatic Gas Generator," D. K. Alpern, J. CHEM. EDUC., 36,302 (June 1959). For the teachers interested in economy of materials, this gas gen- erator will serve well in semimicro nrocess experiments. A diagram and a ohotoeraoh show the desien a-nd ease ofconstruction. o he au- . -. - thor describes an expernnent involving the generatmn of hydrogen which he clams is extremely safe and trouble free. "An Inexpensive and Versatile Kipp's Apparatus," K. M. Chan, Chem 13 News, 4 (October 1977). A simple Kipp's generator may he made with a polyethylene medicine bottle. The instructions for construction are easv to follow and t h ~ diagrams megmd.Thr use of a scrcw.type aquarium valvr allowsgoul cuntnd uf the gas flow, rqperially when n small, but steady. stream is needed. "Making Laboratory Glassware," Alan R. Inversin, Science Activities, 14 (MarchIApril 1977). Far those teaching in very austere situations, this article will he most useful. Some of the suggestions for making heavy-duty glass containers, funnels, watch glasses, etc., are excellent. The techniques needed are well described and are easy to carry out. (I have tried them.) I was fascinated with glassware made from old light bulbs. I have, incidentally, learned from some of my colleagues who teach in high school how to convert plastic soda bottles into useful lab equipment. They have made such item as watch glasses, reaction containers, funnels and even dome-top display containers for mineral specimens or other items used far teaching, where touching of the items is to be avoided. "A Simplified Electrolysis Apparatus," Louis Teichman, J. CHEM. EDUC., 34,291 (June 1957). A plastic refrigerator bowl, two one-holed rubber stoppers, fdament supports from burned out light hulhs,and two testtuhes, assembled and. Voila! an electrolvsis set un for an individual chemistrv student. See the article for a clear diagram for constructing the apparatus. "A Convenient Device for Dispensing Solid Samples in Teachina Laboratories," G. R. Brubaker and G. T. Belinke, J. CHEM EDUC., 46,318 (May 1969). Here's an interesting use of a familiar device ". . . for dispensing solid samples to a large number of students." The authors claim it to "(1) minimize waste by controlling the size of the sample; (2) eliminate contamination; (3) permit facile changes in the size of the dispensed sample; (4) require little or no maintenance; and (5) he sufficiently simple in operation that no instruction in its use is required." It is "Soap Saver," the kind found for dispensingpowdered soap in public washrooms. "An Inexpensive Timer," Eknath V. Marathe, J. CHEM. EDUC., 46,840 (December 1969). A tape recording was made of the sound of "an electric buzzer, operated manually at an interval of one minute and with the tape meed of 1% inehlsec. When the taoe is nlaved hack. it can be used as . .. a timer, giving the sound signal at an interval of 60 sec, 30 see, or 15 see when played back at speeds of 17/8, 3314, or 7% in./sec, respec- tively." "Safety Shut-Off for Water Cooled Devices," R. A. Bailey et al., J. CHEM. EDUC., 41,30 (January 1964). The prohlem of variation in the rate of flow of water is well known both at home and in the laboratory. In many situations where a low level of flow is required, many older water taps tend to "turn them- selves off." This ean be damaging to equipment or to reaction systems being studied. The authors constructed a simple device using a spring-loaded microswitch and a lever arm with a cup attached. The cup has holes toallow water through at a predetermined rate, anything less allows the lever arm to he raised by the spring in the switch and the electricity turns off. Many variations of this set up can he made. The diagram is easy to follow. "A Water Aspirator Hood," Wilbur D. Moore, J. CHEM. EDUC., 36,407 (August 1959). Many teachers forgo experiments and other student lab activities because of lack of fume hood space. Moore has described an easily constructed conical fume h o d connected to an asnirator. Since m a w gases are water soluble, his device is most useful. I have used it in lecture demonstrations in situations where a fume hood was not available. pH Meters "The pH Indicator," John T. Stock, The Science Teacher, 39 (November 1962). One of the first build-it-yourself instruments of importance to teachers of beginning chemistry was the pH indicator designed by Stock under a program for designing science teaching equipment funded by NSF. Several of my colleagues and I have constructed the apparatus according to the instructions and schematics shown in the article, and we have found that the pH indicator works well. Included are instructions on making your own electrodes. "An Inexpensive p H Meter," Dennis Sievers, J. CHEM. EDUC., 58,281 (March 1981). Whereas Stock's meter deserihed above had you make your own electrodes, the recommendation here is to use a commercial one. The one suggested is a combination electrode, which has advantages. The schematic is similar to Stack's and it appears to he quite feasible to build. "Build Yourself a High Quality p H Meter," David Doty, The Physics Teacher 55,574 (November 1978). This article describes a more sophisticated model. I t is much more technical in its circuitry and design. Complete details for cnnstruction are given as well as comments about the circuitry. It appears to he an electronic huffs delight. "Adopting a pH Meter for Lecture Demonstration. Con- struction of an Auxiliary Scale for Overhead Projectors," Jo- seph A. Stanko, Charles G. Haas, and John R. Lotz, J. CHEM. EDUC., 54,365 (June 1977). Specifics of how to convert a pH meter for use with an overhead projector are presented. Volume 61 Number 4 April 1984 385
Transcript of pH meters
mnething new from the pwt
Edited by: JOSEPH S. SCHMUCKLER
Chairman of Science Education Temple University
345 Riner Hall Philadelphia. PA 19122
Homemade Lab Equipment
In this installment of "Something New From the Past," I am in- cluding articles on simple, inexpensive deviceslapparatus that can be constructed in the lab, inexpensive equipment that people such as you have improvised and reported in the journals. Most of the ar- ticles reviewed here are short. Some of the ingenious ideas are even inspirational. I hope that you will share your improvisations with your fellow readers by sending them to the editor of our feature, "Inventory Control:"
"An Improved Gas Generator for Elementary Chemistry," G. W. Thiessen a n d H. Hall, J. CHEM. EDUC., 38,19 (January 1961).
This is a small-scale gas generator, easy to cnnstruct, efficient, and as flexible as a Kipp's generator. "It provides elf-controlled evolution of gas from solid and liquid reagents,with reservegasstorage capac- itv." Waste oroducts are easilv siohaned off. The eenerator is ca~able . . - of almost continuous operation. An easily understandable diagram is provided for constructing the apparatus.
"A T e s t T u b e Automatic Gas Generator," D. K. Alpern, J. CHEM. EDUC., 36,302 (June 1959).
For the teachers interested in economy of materials, this gas gen- erator will serve well in semimicro nrocess experiments. A diagram and a ohotoeraoh show the desien a-nd ease ofconstruction. o he au- . - . - thor describes an expernnent involving the generatmn of hydrogen which he clams is extremely safe and trouble free.
"An Inexpensive and Versatile Kipp's Apparatus," K. M. Chan, Chem 13 News, 4 (October 1977).
A simple Kipp's generator may he made with a polyethylene medicine bottle. The instructions for construction are easv to follow and t h ~ diagrams megmd.Thr use of a scrcw.type aquarium valvr allowsgoul cuntnd uf the gas flow, rqperially when n small, but steady. stream is needed.
"Making Laboratory Glassware," Alan R. Inversin, Science Activities, 14 (MarchIApril 1977).
Far those teaching in very austere situations, this article will he most useful. Some of the suggestions for making heavy-duty glass containers, funnels, watch glasses, etc., are excellent. The techniques needed are well described and are easy to carry out. (I have tried them.) I was fascinated with glassware made from old light bulbs.
I have, incidentally, learned from some of my colleagues who teach in high school how to convert plastic soda bottles into useful lab equipment. They have made such item as watch glasses, reaction containers, funnels and even dome-top display containers for mineral specimens or other items used far teaching, where touching of the items is to be avoided.
"A Simplified Electrolysis Apparatus," Louis Teichman, J. CHEM. EDUC., 34,291 (June 1957).
A plastic refrigerator bowl, two one-holed rubber stoppers, fdament supports from burned out light hulhs,and two testtuhes, assembled and. Voila! an electrolvsis set un for an individual chemistrv student. See the article for a clear diagram for constructing the apparatus.
"A Convenient Device for Dispensing Solid Samples in Teachina Laboratories," G. R. Brubaker and G. T. Belinke, J. CHEM EDUC., 46,318 (May 1969).
Here's an interesting use of a familiar device ". . . for dispensing solid samples to a large number of students." The authors claim it to "(1) minimize waste by controlling the size of the sample; (2) eliminate contamination; (3) permit facile changes in the size of the dispensed sample; (4) require little or no maintenance; and (5) he sufficiently simple in operation that no instruction in its use is required." It is
"Soap Saver," the kind found for dispensingpowdered soap in public washrooms.
"An Inexpensive Timer," Ekna th V. Marathe, J. CHEM. EDUC., 46,840 (December 1969).
A tape recording was made of the sound of "an electric buzzer, operated manually a t an interval of one minute and with the tape meed of 1% inehlsec. When the taoe is nlaved hack. it can be used as . . . a timer, giving the sound signal at an interval of 60 sec, 30 see, or 15 see when played back at speeds of 17/8, 3314, or 7% in./sec, respec- tively."
"Safety Shut-Off for Water Cooled Devices," R. A. Bailey e t al., J. CHEM. EDUC., 41,30 (January 1964).
The prohlem of variation in the rate of flow of water is well known both at home and in the laboratory. In many situations where a low level of flow is required, many older water taps tend to "turn them- selves off." This ean be damaging to equipment or to reaction systems being studied. The authors constructed a simple device using a spring-loaded microswitch and a lever arm with a cup attached. The cup has holes toallow water through at a predetermined rate, anything less allows the lever arm to he raised by the spring in the switch and the electricity turns off. Many variations of this set up can he made. The diagram is easy to follow.
"A Water Aspirator Hood," Wilbur D. Moore, J. CHEM. EDUC., 36,407 (August 1959).
Many teachers forgo experiments and other student lab activities because of lack of fume hood space. Moore has described an easily constructed conical fume h o d connected to an asnirator. Since m a w gases are water soluble, his device is most useful. I have used it in lecture demonstrations in situations where a fume hood was not available.
pH Meters
"The p H Indicator," John T. Stock, The Science Teacher, 39 (November 1962).
One of the first build-it-yourself instruments of importance to teachers of beginning chemistry was the pH indicator designed by Stock under a program for designing science teaching equipment funded by NSF. Several of my colleagues and I have constructed the apparatus according to the instructions and schematics shown in the article, and we have found that the pH indicator works well. Included are instructions on making your own electrodes.
"An Inexpensive p H Meter," Dennis Sievers, J. CHEM. EDUC., 58,281 (March 1981).
Whereas Stock's meter deserihed above had you make your own electrodes, the recommendation here is to use a commercial one. The one suggested is a combination electrode, which has advantages. The schematic is similar to Stack's and it appears to he quite feasible to build.
"Build Yourself a High Quality p H Meter," David Doty, The Physics Teacher 55,574 (November 1978).
This article describes a more sophisticated model. I t is much more technical in its circuitry and design. Complete details for cnnstruction are given as well as comments about the circuitry. It appears to he an electronic huffs delight.
"Adopting a p H Meter for Lecture Demonstration. Con- struction of an Auxiliary Scale for Overhead Projectors," Jo - seph A. Stanko, Charles G. Haas, a n d John R. Lotz, J. CHEM. EDUC., 54,365 (June 1977).
Specifics of how to convert a pH meter for use with an overhead projector are presented.
Volume 61 Number 4 April 1984 385
