Notes on Qualitative Analysis EDITOR'SNOTE: The following papers have heen collected over a period of months. A similar collection appeared a year ago (J. CHEM.EDUC.,35, 401 (1958)). It is the Editor's hope that collection into one place will prove more attractive to readers than the more frequently used editorial procedure of scattering items sueh as these through the pages of sevwal issues. We apologize to authors who thus have had to wait to see their work in print. We commend to readers' attention the fact that sseveral of these represent the sulution of problems given t o freshman students in quditativo analysis courses. We hope t , h t publication in these pages can stimulate just sueh activity. If reeders merely incorporate these ideas into their own laboratory instructions, our battle is only half won. If, beyond that, these ideas suggest to ~ gratiiied. the readers t h a t t,hey use their o r n inpennit,? in similar f s ~ h i o na, . are
Stephen P. Marion and Isaac Zlochower Brooklyn College, Brooklyn, N. Y.
This procedure may be used for the direct determinat,ion of the Group 111 cations, for a quick confirmation of the results obtained in the regular scheme of analysis, or for teaching another technique in amlytical chemistry. With little practice the average student can do an unknown in about an hour. In the method offered here, the available spot tests have been selected and arranged such that each Group 111 cation may he detected in the presence of all the others provided these cations are present in approximately the same molarity. An alternate method utilizing most of these tests as paper spot tests is provided. The prepared papers are usually more stahle and are easier to store and to dispense to the student than are the reagents. .%bout 250 students have tried these tests over the past few years on unknowns containing about 1 mg of cation per ml. On the average these students did almost as well on this more rapid method as they did in the more time-consuming traditional method. Since this procedure is designed for a beginning course, interfering anions such as horates and phosphates are not present, nor is organic matter usually in the unknown. Students are instructed to try these tests on solutions containing the individual cations until they are familiar with the appearance of positive results. Then they practice on a known solution containing all these Group I11 cations. The tests are conveniently performed on a spot plate using small drops; quantities are increased only if the results are vague and indefinite. There is no preferred order in which these cations may be determined. Nickel
Reagent: 1% dimethylglyoxime in ethanol. To a drop of the test solution is added one drop of conc. NHz and 2 or 3 drops of dimethylglyoxime reagent. The formation of a oink or red color on the m.o t d .a t e indicates nickel. If the results appear to he negative, add another drop or t,wo of NHs hefore discarding.
A Spot Test Analysis of the Group 111 cations Paper spot test: Filter paper is soaked in 1% dimethylAdro~ of conc. NH. is added ro the di~nrthylglyuvilnppaper. T o r1.m is added n drop oi thr l ~ ~sr\.~r8lmore solutiuu u d e r tlw, f~IIow(.d1,s the i t d ~ l i f i (d drupr of NH,. If nirkcl is prrsrrlr a I,ri
