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Edited by: JOSEPH S. SCHMUCKLER Chairman of Science Education Temple University 345 Riner Hall Philadelphia,PA 19122
Acid Base Indicators
Acid-Base Theory "Demonstrations for High School Chemistry," [Acid-Base Theory], Joseph F. Castka, J. CHEM. EDUC., 52 [6], 3 9 0 9 5
(1975). "These demonstrations and the sequence in which their presentation is suggested may serve to initiate and maintain student interest in such topics as.. .the development of acid-base theories.
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pH Concept "Development of t h e p H Concept, A Historical Survey," Ferenc Szabadvary, translated by Ralph E. Oesper, J.
CHEM.EDUC.,41 [2], 105-107 (1964). The discovery that colored "juices" extracted from plants "reddened" upon the addition of acids was discussed by Robert Boyle in 1680. Many other recognizable early scientists also experimented with acid solutionsMeyer, Gay-Lussac,Bethollett, Gulherg, Waage, and others. The origin of the word "buffer" is mentioned as is the origin of the pH hy the famous Danish Biochemist, Sorensen in 1909: "For the sake of convenience he suggested that instead of hydrogen ion concentrations their negative logarithms he used. He called them hydrogen ion exponents and suggested that they be represented by the symbol pH." The article shows that the use of the pH concept spread in biochemistry and related fields but that chemists were slower to accept its significance.
Chemical Querieson pH Question: "According to the definition, p H = -log H+, there is no mathematical reason why one can't have a negative p H Is such a thing possible?" This question submitted t o J. A. Young a n d J. G. Malik in 1969 was answered in their column Chemical Queries . . e s ~ e c i a l l vfor introductorv chemistrv teachers. See J. CHEM. 36 (1969). E ~ U C .46'[1], , "The DH Conce~t." 111. . . Doris Kolb. J. CHEM. EDUC.. . 56 ...
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"Indicators a n d t h e Basis for Their Use," George Gorin,
J.
CHEM. EDUC..33 171.318-319 (1956). . . For the chennisfry rrnrher whoren~znizcithe need ro know n lirtle mwc tlmu w h ~ hew r she wachei, (hrin's.lrtirlr mn fulfill rhat need regarding the useof indlcnror- inncid-h~sctifration. Theauthorsnys that he has found an encouraging response to his way of teaching& explaining the choice of an appropriate indicator for volumetric determinations. because the student understands intuitivelv the areuu ment hased on competitive relationships between unknown reagent and indicator."
Applications in the Classroom "The p H of Hair Shampoos: A Topical High School Experiment," F. Corcoran and Kenn A. Akoha, J. CHEM. EDUC.,
54 [9]553-554 (1977). Students were invited to bring in different hair shampoos and related toiletries for pH determination. The measurements were made with a Chemtrixa, type 40E, pH meter. The authors give details of their procedures and a table of their results. They 'discuss briefly the chemical action of shampoos, the composition of hair "dirt," and of the shampoo molecules.
"The Chemistry of Toilet Bowl Cleaners," C. H. Breedlove, Jr., Chemistry, 46 [lo], 31-32, (1973). Breedlove shows that "these cleaners are mostly composed of inexpensive chemicals that undergo simple straightforward reactions." He describes the two major types of bowl cleaners and presents the chemical equations for the reactions that occur. It is an excellent article to hring relevancy to the beginning chemistry course.Excellent consumer information can be eleaned for the student: for examole.
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49-53, (1979).
Consistent with her style ofwriting and continued high quality of contributions to chemical education, Kolb presents a paper that will prove ta be most valuable to the teachers of beginning level chemistry. She has included charts and diagrams that can easily he duplicated, enlarged, and used as teaching charts. She presents detailed caleulatians of pH from [H+] for weak acids, bases, and salt solutions. Kolb discusses buffered solutions and the measurement of pH. The "color wedge" of Niels Bjerrum is described for measuring pH using indicators. It can make an interesting project for students. Included also is a brief history of the pH meter.
Buffer Solutions "An Easily Prepared Wide Range Buffer Series," Walter R. Carmody, J. CHEM. EDUC.,38 [ll],559-560 (1961). The high east of pH meters, repair and replacement parts, makes Carmady's paper, once again, timely. He says that the useof "mixed indicators capable of indicating the pH of solutions over wide ranges has greatly increased the posihility of designing new significant demonstrations and experiments." Carmody developed a series of buffers with pH values from 2.0 to 12.0 requiring the preparation of only two stock solutions and the use of only two or three common chemicals. An ordinary graduated cylinder can he used. A chart is given showing needed volumes of solution "A" and " B to prepare 200 ml of buffered solution with pH values from 2 to 12 in 0.5 pH value increments.
to bring out the potentially dangerous consequences of mixing an acid-containing cleaner with a chlorine hleach. He might havementioned too the potential toxic dangers of o d i c acid, a stain remover contained in some howl cleaning products. "The Senses are Indicators in Volumetric Analysis,'' J. P. Phillips, J. CHEM. EDUC.,35 [I],35 (1958). This mmt interesting article describes the uses of the senses of sight (already well used), smell, touch, and-believe it or not-hearing in volumetric analysis. It is a short article and worth reading by those innovative teachers who might want to pursue alternativesto the sense of sight when determining end points during titration.
Innovation Next is a short article t o serve a s a reminder t h a t improvising equipment is not a new "art." I n t h e times of tight budgets of a generation ago, many of u s enjoyed t h e fruits of each other's ingenuity. Over its years of publication, J. CHEM. EDUC.has printed many short articles based o n a chemistry teacher's innovative ingenuity. If you have such a tested item, send i t in t o t h e editor of this section, Mickey Sarquis, Miami University, Middletown, O H 45042. "Titration Without Burets," Shirley Gaddis, J.
EDUC.. . 36 161. . .. 290 (1959).
CHEM.
(hddi~'suzgexmnc,ffers rhs uss ofsmall polyethylene bottlrs [that can cas:ly Ire cd~hratcdro wnhin 0.1 unm1 to ierw for titrcrion e x prrirnrnt
