I have a part-used bottle of HC110, the syrup type. There is still a large amount in the bottle, but it is way out-of-date. I think it expired in 1997. I have tried it and it still seems to work. Can anyone tell me if it should work as intended, or if there is likely to be some form of deterioration in its quality? Is it a case of it either works, or not, or is it likely to develop the film but give a lesser quality result? I will use it if is capable of giving results to the original standard. I don't want to throw it out if it can be used. Thanks for any advice. Alex.