INQUAL-S is a simulation of inorganic qualitative analysis using the insolubility of sulfides as the main avenue to separation. This simulation allows for the identification of eighteen common cations in a mixture of their nitrates. The separation and testing methods used by this software allow the user to approximate those of Hogness, Johnson, and Armstrong (1) and to a lesser extent, those of King (2).

INQUAL-S allows students to start with a solution of known identity with 1-18 cations or with a sample containing from 1-10 cations that are randomly selected by the computer and not known to the user. The cations are divided into groups depending upon whether they give insoluble chlorides, acid insoluble sulfides, base insoluble sulfides, insoluble carbonates, and none of the previous classes. Each group is then subjected to a variety of reagents to individually identify each cation.

If the suggested scheme is followed, INQUAL-S reproduces the expected behavior of these cations and results in the successful identification of each cation present in the original mixture. However, INQUAL-S allows the user to add any of the reagents supplied in any order and in any amount. So, just as in the real laboratory, a wrong reagent at the wrong time in the wrong amount can lead to results that can be very difficult to interpret.

In addition to the 29 reagents that can be added, the user can filter, heat, evaporate and run flame tests (with or without cobalt glass) on the sample. During the simulation, volatile reagents will be lost on heating, carbonates will bubble on contact with acid, and precipitates will separate and redissolve.

With 18 cations and 29 reagents, the number of possible variations of solution and precipitates is very high. While the author has attempted to anticipate all possible reactions, it is almost certain that some have been overlooked and others misrepresented. Nevertheless, the program will mimic all the common behaviors of these combinations of cations and anions as the acidity and ammonium ion concentration of the solutions change.

INQUAL-S is intended for use by high school or first year college students of chemistry. Those users will see the colors of the commonly precipitated solids of inorganic chemistry and the solubility rules that govern their precipitation, and should develop skills in interpreting the behavior of cations under a variety of reaction conditions.

This screen from INQUAL-S shows what happens when hydrochloric acid is added to a mixture of cations to be separated and identified. The strip at left is pH paper indicating the approximate pH of the contents of the test tube. The list at right gives choices for the next step.

Literature Cited

1. Hogness, T. R.; Johnson, W. C.; Armstrong, A. R. Qualitative Analysis and Chemical Equilibrium, 5th ed.; Holt, Rinehart and Wilson: New York, 1966.
2. King, E. J. Qualitative Analysis and Electrolytic Solutions; Harcourt, Brace: New York, 1959.