In order to test whether the ferric oxalate is still good I have I found (in this book) there is a thing I could do: I dissolved three drops of it in 20ml of water, then added a solution (10%) of pottasium ferricyanate. If it became blue, that would mean that it was worthless. The solution of ferric oxalate was yellow (like urine ). The potassium ferricyanate solution was also yellow. When I added the one in the other, it stayed yellow. Does this mean that my ferric oxalate is still good ?