a- 1 CHEMICAL PROJECTS feature

Research Ideas for Young Chemists Compiled by JAY A. YOUNG, King's College, Wilker-Barre, Penno. I JOHN K. TAYLOR, Nationol Bureau of Standards, Washington, D. C.

Determination of Saponification Equivalents of Phenolic Esters See TOBEY, S. W., el al., J. Chem. Educ., 38, 611 (1961).

I n the identification of compounds many different properties When determining the saponification equivalent of phenolic can be used such as molecular weight, color, infrared absorption esters which have n nitro substituent on the aromatic nucleus, characteristics, behavior in various chemical environments, thymolphthalein should be used as the indicator in the hack and others. One identifying feature, often used for esters, is titration step because most substituted phenols have pK values the weight (in grams) of ester per equivalent of base needed less than X 2 . Can you find any phenolic esters with a nitro to saponify the ester. This ratio is called the "saponification suhstituent on the aromatic nucleus for which thpophthalein equivalent." Phenolic esters often do not yield reproducible is not required as the indicator in the back titration step? Or, s.qxmifieation equivalents when the procedures described in can you find any other aromatic esters, in addition to those various reference works are used. The t~uthors have developed mentioned by the authors, which are not nitro derivatives of a procedure which does give reliable results with phenolic or phenol, for which thymolphth~lein is required as an indicator in any other esters. the back titration step?

Can you succeed where the authors failed, and develop a Questions: mixed indicator which would besuitable for both types of phenolic

The authors state that they are not sure why the older pro- esters, those with phenol derivative moieties with pK values cedures far the determination of the saponification equivalent above, and below, 9.2? of sn ester often fail with phenolic esters, though they do suggest The saponification equivalents of carhoxylic acid esters of afew possible reasons. Can you establish that one or more of the polyhydroxyl aromatic compounds and of esters of p-hydroxy- reasons they suggest are valid, or, can your determine some other benzoic acid and p-hydroxycinnamic acid cannot be determined explanation? by the procedures described. Can you devise s. suitable pro-

The authors indicate that phenolphthalein cannot be used as cedure for one or more of these classes of esters? an indicator in the hack titration step of their procedure since NOTES: The investigations suggested by the questions here are phenol is itself acidic enough to react appreciably with the base recommended for the student who has a strong interest in, and before the phenolphthalein has changed color. Therefore, they comprehensionof, organicchemistry andanalyticalchemistry. recommend the use of another indicator. Phenolphthalein The use of tris(hydroxpethyl)aminon~ethane as a primary could he used, however, if before the back titration the phenol standard, though recommended, is not mandatary. See THIS

were tied up chemiertlly in some way so that its acidic character J o m a ~ , 36, 297 (1959). Similarly, apparatus with standard would not he evident. Can you suggest a. practical scheme for taper joints will facilitate the experimental work but is not accomplishing this result? essential.

........................................................ A Biochemistry Laboratory Experiment See SCREE, I., el al., J . Chern. Bdue., 38,632 (1961).

When an electrical discharge is passed through a gas or mix- tures of gases, new products m e often formed as a result of the action of the electrical discharge. It has been postulated that prior to the existence of life on the earth, an analogous natural oroeess orodueed the essential cam~onents for livine forms. which

for several days through a mixture of ammonia, water vapor, and ordinary burner gas.

Question: Construct an apparatus similar to that described in the article

and hll i t with a suitable gas or gas mixture. Pass an electrical discharge (a spark coil from a. "Model T" Ford-these are still xvailahle a t reasonable cost-can be used instead of the induction coil recommended) through the gas for a suitable period of time, and identify as many of the products formed as possible. AF count for the formation of these products and test your sugges- tions by further laboratory work. NOTE: Since explosive mixtures of gas may inadvertently be used initiallv or might be formed during the course of a run, be sure to use safety shields and to wear safety goggles when con- ducting this investigation.

A Constant Current Source for Student Use See MANN, C. K., AND CHAMPEAUX, V. C., J. Chem. Educ., 38, 519 (1961)

For many modern studies in quantitative analytical chemistry constant current source is described. Na specific suggestions a source of constant current is necessary. Mast of these studies are made for its usein an experimentalinvestigation. comprise investigations in one of these fields: coulometric titra- tion a t constant current, potentiametric titration a t constant current, ohronopotentiometry, and current scanning potentiom-

Construct the constant current source described and use it to help solve a problem posed in another chemical project in this

etry. Of these the first is probably the simplest for a beginner to ~t is s u g g e ~ d that the first problem you select involve a study. titration which you can adapt to 8 constant current conlometric

I n the article, the oonstruotion of an inexpensive transistorized titration.

A986 / Journal of Chemical Education