ION-EXCHANGE PAPERS Submitted by Joseph A. Sherma, Jr , Lafayette College, Easton, Pa. Checked by Robert R. Greve, Michigan State University, East Lansing PREPARATION
Prepare saturated solutions of iron(II1) nitrate and mbalt(I1) chloride in 6 N HC1. Provide a 20 cm test tube with cork stopper to fit, and strong base anion-exchange paper in the chloride form (Grade SB-2 supplied by Rohm and Haas Company or "Reeve Angel Company and containing Amberlite IRA-400). DEMONSTRATION
Cut a strip of ion-exchange paper PI4 X lK1Iacm and staple one end to the underside of the cork stopper. Put two staples on the other end of the paper to act as a weight and cause the paper to hang straight. Mix equal quantities of the two solution5 and with the tip of a stirring rod apply a small spot of the mixture approximately 4 cm from the free end of the paper (As an alternative, the sample can be applied as a streak across the entire width of the paper.) Dry the spot thoroughly
Fit the cork into the test tube which should contain enough 6 M HC1 to fill it to a depth of about 4 em. There should be about 2 cm between the level of the solvent and the spot on the paper. In a few minutes the solvent front will ascend through the spot and effect a complete separation. The less strongly complexed (by chloride) cohalt(I1) will be carried up the paper leaving the more strongly complexed iron(II1) near the origin REMARKS
The demonstration described is convenient because it is rapid and both solutes are colored. However, other separations possible on columns of ion-exchange resin can he reproduced as above on ion-exchange papers. For example, the halides can be separated on SB-2 paper in the nitrate form by development with 2 M NaNO?. The spots are revealed by treatment with AgNOf and photographic developer solutions i
d of Chemical Educalwn
October 1962
DEMONSTRATION NOTES From time to time Hemssuch as thefollowing which do not require a full half-page, will be listed together. Some of them will be modifications of previously published demonstrations, in which case it i s swlgested that they be clippedandattached to the pertinent experiment.
REVERSION OF THIOUREA TO AMMONIUM THIOCYANATE
PALLASSANA AXAXTHARAM.~X ~ E E T H A K A M . ~ Xof The New College, Madras, India, suggests a comparison of the behavior of t.hiourea with that of urea. [See "Reversion of Urea by RODERICK SCHEER,J. CHEM. EDUC.,34, A575 (1957) or "Tested Demonstrations in Chemistry" (4th ed.), page 64 (1960).] A few grams of urea held in the molten state in a test tube in a paraffin bath at 170' for 5 min is cooled and extracted with 10 ml of hot. water, The resulting solution gives a red color wit,h iron(II1) chloride and a precipitate with silver(1) ion: it is a conductor of electricity. Thiourea solut,ions do not. show this behavior. IRETXOLDS, -1. Chem. Sec., 22, 1 (1869); REYNOLDS
I\D MAN,
WERKER, J. Chem. Soc., 83, 1 (1903), SEETHURAP. A,, School Science Renew, 42, 529 (1961).]
TRANS ELIMINATION
P. M. THOMAS of St .Joheph's College, Tiruchirapalli, India, illustrated the elimination of water from henzaldoxime as follows: "I had my pen in the chest pocket on the left side. I removed the pen with my right hand and put it back I did the same with my left hand." SPONTANEOUS COMBUSTION OF HzS
Place about 10 g of dry lead (IV) oxide in a porcelain dish. Pass a jet of hydrogen sulfide gas directly onto the oxide. The gas bursts into flame in a few seconds. Submitted by P. M. THOMVS (see above).
l " , , , a f of Chemzcal Education
October 1HSS
