My solution looks like this: The basis is to assess, inter alia, the purity of the product. The Namely, depending on the purpose, have disastrous or beneficial effects on the desired results. Each percent less than 99% will thus lead to star deduction.
A price comparison, I will also draw for evaluation. If the substance is low, or there is the same product cheaper elsewhere?
Of particular importance, I find also product safety. If the powder is perfectly packaged, or you get the stuff already when opening the shipping carton against sprinkled or dripped? If the packaging is fit for the future, or it can be expected that the substance will have eaten in 5 years? Is -in particularly dangerous Stoffen- a parental attached? -Or To children's hands easily turn up the container?
I find so when the criteria mentioned defects, there are asterisks deduction.
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