Computer Assisted instruction in Qualitative Analysis Recently, computers have been used as teaching aids in chemistry. Computer teaching methods are very useful for the development of student understanding through drill. Computers have already been utilized successfully for drill in organic chemistry.' The construction of an organic drill program which employs a reagent matrix to represent a set of successive one-step transformations has been previously d e s ~ r i h e dThis . ~ matrix technique (essentially a table look-up procedure) has been similarly applied towards the teaching of the qualitative analysis scheme; an interactive Basic Program has been developed for a 4K PDP-8 time-sharing environment. The qualitative analysis scheme followed is the one presented by Sorums containing 22 cations distributed into four groups. The groups are: Group 1: Agt, Pb2+,Hg,Yt; Group 2: C$+, A$+, HgZ+,BiS+,CdZt, ShBt, Sn4+;Group 3: AP+, Ni2+, Fe"+, Cr", Mn'+, Zn2+, Co2+;Group 4: Ba2+, Ca2+,Mg2+,Nat, Kt. Each cation has a number. A reagent matrix is set up of size 22 X 22. This matrix allows the student to select a sample containing any two of the possible cations. The code numbers of the i-th and j-th cation specify the ij-th element in the reagent matrix. In actual practice the 22 X 22 matrix is partitioned into four distinct matrices each containingcations of the samegroup: a 3 X 3 matrix, two 7 X 7 matrices and a 5 X 5 matrix. This saves core space because all cations of Group 1for example are separated from the other cations by the Group 1 precipitat~ngreagent. The numerical value of the ij-th element in the reagent matrix, C, is fed into an "on C Go To" statement which directs the program to a certain line number. At that line number a print statement lists the reagent needed to separate cation i from cation j as well as additional information such as the chemical formula and color of any precipitates. Once the student sees how the separation is completed, each of thetwo cations can he identified via an identification vector. This vector, of size 22, contains a list of identification tests. The numerical value of the vector location directs the program to he a specified print statement. Information such as "KSCN: Fe(SCN16 - - - blood red solution" would be printed if the student selects the cation code numher of Fe"+. The Basic strinemaninulative facilities allow the moeram to run under the euise of a dialoe.usine,. the student's name. ., Such "prrsonal" fcnrures coupl~d~ o s ~ u d IIIIPTP
