MELTING POINT DEPRESSION Submitted by: Ascanio G. Di P~ppo'and Sister Miriam Joseph, R S X , Salve Regina College, Newport, R. I. ChecLed by: Duncan Reed, Fulton Co~nm.High School, Fulton, Ill., John A. Meegan, Framingham Senlor High, Fran~inghan~, Mass., and Michael J. King, Alemany High School, San Fernando, Cahf.
PREPARATION
REMARKS
1 3 q a r e we~ghcdsamples of 0.4 g pqx~rorial(mp 3537') and 0.1 g resorcu~ol ( n ~ p110-111'); provide a 150-111m test tube, and a the~mon~etcr.
The eutectic tcnlperature of this system is well below room temperature. When mixed geutly and allowed to staud undisturbed, mixtures of piperonal and resorcinol in the proportioris, 0.9 g/0. 1 g, 0.8 g10.2 g, 0.7 g/OJ g, 0.8 g/0.4 g and 0.5 g10.5 g melt almost complctcly withiu 15 m i ~ ~ u t e sdroplets ; can be observed in about two minutes and the melting process proceeds rontim~ously thereafter. For other systems with low eutectic temperatures see THIS JOURNAL, 37, A360 (1960); see also "Tested Dcmonxtrations," 5th ed., Chen~icalEducation Publishing Co., Easton, Pennsylvania, 1962, p. 181.
DEMONSTRATION
Add the samples to the test tube 111 layers or gently blend then1 with a metal spatula so that the plpcronal 1s not melted, Droplets of liqu~dform in about two n~inutes. Temperatures may he taken a t two-mnute intervals.
ENANTIOTROPIC FORMS OF COPPER(1)MERCURY(I1) IODIDE
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S'ubnzztted by: W. J. Hughes, University of Liverpool, Liverpool, England Checked by: David B. Moss, Eiranl College, Hiram, Ohio PREPARATION
Precipitate mercury(11) iodide by mixing 3.4 g niercury(I1) chloride in 50 n11 water aud 4.2 g potassiuin iodide in 25 nd water. IXter and wash the precipitate with water; then dissolve the precipitate in a similar amount of 4.2 g KI in 25 ml water. Mix the filtered solution with 12 g hydrated copper(I1) sulfate in the minimum volume of water. Reduce the mixture with SO2 gas and wash the resulting precipitate with water, followed by acetone; dry a t 90°C DEMONSTRATION
Smear a piece of filter paper wlth a small amount of the bright red cor)per(I)-mercury(11) iodide. Hold the smeared filter paper over a source of heat, such as a tllted hot plate or a small flame When the dark brown copper(1)-mercury(11) ~odldeforms, remove the
paper from the heat and allow to (
