The Identification of an Unknown Alloy-A
First Experiment in Elementary Chemistry
The experiments which are often used as an introduction to the laboratory in beginning chemistry courses are considered by many students to be sheer busy work; even conscientious students find little interest or challenge in measuring lengths and volumes far density calculations. The following experiment was devised to provide students with an interesting and meaningful introduction to the laboratory. This experiment has been used successfully in bath science-major and in science-minor courses. Most of t,he students are able to complete the experiment.in G O br. The experiment must be introduced by the instructor previous to the first working laboratory period. In this introduction, the instructor arouses the students' interest in identifying the components of some alloy, be discusses possible methods for determining charseteristio properties of substances, and he assigns each student to bring to the Innurntory .;NIW nlctallir objert which I he S I I I ~ C I , Itiuold like ro :~n;tlyire. ~ lor ilrtrrminino.pn,l,ertici mrh sc rclnrwc hnrilnw, I,:arh studrnt drvivs, nith rsr wirhout help, hi. o u . m~lhod; I I C ~ ~ I I \altd . . itptrrozimate rnrlline ilrnint. lip inen.surer there ~ r o ~ r r t iofe si l i a obirrt n1.d thnt wf w n d c * ul k n o w elehe makes a tenstivLgu& as to the identity of the element^-in his alloy. ments: ~ro'a comparison of The student then attemots to dissolve aoieee of his ohiect in an acid: wine first cold. dilute HC1 and. if necessarv. .. plwc~dlng.st(.~)wi~e 1 0 11111, #.;mmrrrled 1lh.h or 3qun rcgin. Thc 311.iolvc pnrt ol rhcol,jecr i u IICI and x n c h - ~ .prrt i l l IIUO,.) After tht.alloy i- d i ~ i o l ~ e~~hlr,~ o l u t i oiandllurcd 2nd rwutcnlixcd wirh KH,i)lI. Thijulution is wrd for the vheroic:,l tests described below. A table is prepared on paper ingrid form with the reagents listed horizontally and the individual ions and two unknowns listedvertically. (The reagents used m e : conc. NH,OH, 6 MNsOH, 0.2 M KsCrO
