求翻译：With free base meth now obtained, the next step, as usual, is to form the crystalline hydrochloride salt of meth. To do this, a few hundred mls of toluene is added to the batch, and the meth free base extracted out as usual. If the chemist's cooking has been careful, the color of the toluene extract will be clear to pale yellow. If this is the case, the product is sufficiently pure to make nice white crystals just by bubbling dry HCl gas through the toluene extract as described in Chapter 5. If the toluene extract is darker colored, a distillation is called for to get pure meth free base. The procedure for that is also described in Chapter 5. The yield of pure methamphetamine hydrochloride should be from 100 to 110是什么意思？

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