"Experimental Observation of pH 7"
To the Editor: I n attempting to verify experimentally the conclusions of the "Preparation of Solutions in the p H Range of Approximately -47 to +47" (J. CHEM. EDUC.,48, 776 (1972)), we obtained some dramatically different results. We observed the pH to differ significantly from the theoretical values as proposed by Pilar. I n fact a limiting pH of approximately 7 was reached as infinite dilution was approached. Perhaps this observation was incorrect cither because we had only approximately 2.36 X loa? molecules of water (Lake Winnebago) available for dilution or alternatively because our glass electrode only registers pH values between zero and fourteen. One colleague even absurdly suggested that the buffering action of water itself a t extremely high concentration may in fact limit the observed pH to the region of seven. ROBERTA. ARNOTT
W. KEVINBRATTON ELROYW. POST JACOBH. PROPP UNIVERSITY OF WISCONSIN-OSHROSH OSHKOSH, WISCONSIN
Fiber Tipped Pens as Chromatography Experiment
To the Editor: It was suggested in THIS JOURNAL [49, 335 (1972)], that samples from fiber tipped pens are excellent for demonstration of chromatography as the colofs are visible during separation. May I further suggest the use of such samples to let the student experience the struggle as well as the excitement of discovery. To do this, discuss the principles of chromatography and then allow the student t o find the proper proportions of alcohols, water, and p H that produce the best separation. I n our laboratory, we used 250 ml beakers, plastic coffee covers with a slit for a strip of filter paper, and 20 ml of solvent (water and ethyl andn-propyl alcohol). With such material the process of separation is quite visible and takes about 20 min. If a thin layer is used, the errors of non-saturation are easily visihle. PHILIPKASIMER QUINNIPIAC COLLKDI: MOUNTCARMEL AVENUE HAMDEN, CONNECT~CUT 06518 (Continuedon page 160)
158 /Journal of Chemical Education
