I've been reading this whole thread and it strikes me as to how different the outlook is between industrial chemists working in pharma to GMP and those of us who do not.
However the compounds delivered for public use still need to be approved. S there is really no use for sloppiness. As a customer I would expect a product that I ordered to conform.
It can be likened to the garage replacing the oil in your car with some other oil that was "not quite correct", what would you say when the engine crapped up? Or something in the petrol that should not be there just because the operator dumped in half a bag instead of doing it properly.
I'm sorry disco but this is utter tripe.
The vast majority of chemicals produced by the chemical industry are used by other industries not by the public. They are used to do a job and batch to batch variability is built into the product specification. If the customers process/product can not work with material from either ends of the spec they need to work on their process/product.
Chemicals are tested for their physical and chemical properties but they do not have to be approved by anybody and minor batch to batch variability is not part of that test regime.
We are not talking about sloppiness we are talking about efficient manufacture and not weighing to the nth degree just because a bench chemist did so when they first made the product 10 years ago.
As a customer you have the right to a product that meets the specification and that's it.
With the products I make the process can be changed every batch if I feel like it as long as we meet the final product spec agreed with the customer (which I wrote to match with what I judged we can produce consistently). I'm looking to make each process as cheap as possible. That might be reducing raw material usage or batch times. Using a small excess of a cheap reagent may be cheaper than the extra time taken to weigh it out accurately.
Pharmaceuticals are different because they interact with a very complicated chemical factory in the human body. As we do not understand all those interactions we seek to standardise the drug manufacture from batch to batch hence GMP. Once the drug has been approved the process is pretty much fixed.
I have deliberately set up processes to work to full bags/drums/IBC's of reagent to remove possible charging errors and to save time. If you understand what is going on in your process that is a perfectly acceptable step to take for some reagents. You might do it for operator ease of charging or because the reagent has a short shelf life etc etc.
It's a lot easier to throw in 10 full 25kg bags of sodium bicarbonate to make the pH alkaline in every batch than it is to add enough to give a pH of 8-9 for each indiviual one. If having collected the data you find the charges have all been between 230 and 240kg that 10-20kg of bicarb in excess costs peanuts but the time and hassle saved is worth much much more.
Do not assume that everything needs to be precise, in reality most things do not. With drugs we're not as sure which things really are important so GMP makes them all important but for the rest of the chemical industry that is overkill that would cost most things out of existance.