求翻译：Another problem with this method is that it can produce a pretty crude product if some simple precautions are not followed. From checking out typical samples of street meth, it seems basic precautions are routinely ignored. I believe that the by-products in the garbage meth are iodoephedrine, and the previously mentioned azirine. If a careful fractional distillation is done, these products can be removed. They can be avoided in the first place if, when making hydroiodic acid from iodine and red phosphorus, the acid is prepared first, and allowed to come to complete reaction for 20 minutes before adding the ephedrine to it. This will be a hassle for some, because the obvious procedure to follow is to use the water extract of the ephedrine pills to make the HI in. The way around the roadblock here is to just boil off some more of the water from the ephedrine pill extract, and make the acid mixture in fresh pure water. Since the production of HI from iodine and red phosphorus gives off a good deal of heat, it is wise to chill the mixture in ice, and slowly add the iodine crystals to the red phosphorus-water mixture.是什么意思？

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