Gracias Mike (Dr. Ware, I am assuming) for the response. I figured it was something like that. It make sense, particularly in a college lab situation. You don't want to be buying fresh chemical for every semester.
Regarding ferric lactate, I would have to get some lactic acid. Since ferrous lactate is water soluble, perhaps it will be more suitable for a water-developable process like cyanotype or ziatype. Speaking of stability, I actually did notice that the first solution I made of ferrous lactate, it sat for a few weeks and then when I added some oxalic acid, no yellow precipitation took place. When I added some potassium ferrocyanide to it, it turned blue - signifying that it had oxidized right in the bottle. When I added the ferrous lactate powder straight to oxalic acid solution, I got nice yellow precipitates that when washed, filtered, and dried looks like this:
(Nice to be able to attach a picture!)
Next will see if I can convert this powder into ferric oxalate solution.
This made me think of a new question: I wonder if I can make mixed ferric lactate/oxalate with the latter providing the extra anions when Fe(2) is oxidized to Fe(3). That way I don't need to get a new chemical (lactic acid) and the whole thing can be done in 1 pot / 1 step.
P.S. gatactotype - is it a thing? why ga?