Well, the answer appears to be that freezing a ferric oxalate solution does not negatively impact its working qualaties in Pt./Pd. printing. In early February I froze 150 ml of a 25% ferric oxalate solution. Well, I thawed it out yesterday and from what I can see the freezing did no harm at all. Granted, I did not do any before and after sensitometry tests so my finding is based merely on experience and eye-balling the results, but from what I can evaluate the thawed out ferric oxalate solution is giving results identical to a fresh solution I mixed about a month ago.