sublimation experiment... interpreting results?

This is probably a pretty basic question, but I am really confused on how to interpret the results of a sublimation experiment.

I tested samples of solid CaCO3, solid NH4Cl, and a mixture of the two by 1) heating the mixture and collected sublimed solids on a watch glass, and 2) by adding HCI to unheated samples of those two separate solids and a mixture of both and observing the reactions. 3) I then tested the collected solid from the first heated sample by adding HCI to it and observed the reaction as well.

Okay, no problem, I followed the directions, and observed the reactions. but I have NO CLUE how to interpret the data to identify what the collected solid is.

I'm not looking for the answer, because if I can't figure it out then I'm not learning anything in the process. But what do I need to compare? I'm looking at how the solid samples reacted with HCI, how the mixture reacted with HCI, and how the recovered solid reacted. I know one of the substances sublimed (went from solid to gas) when heated, but how do I go about figuring this out?

Any help would be GREATLY appreciated. I've got my first lab practical today and I need to understand this!