This is a centuries-old industry, governed by the world’s oldest food law, the 1516 Reinheitsgebot (purity law).

这是一种世纪工业，由世界最古老的食品法——1516 年《德国啤酒纯度法》指导的工业。

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The institute that looks after the secret-service archives is concerned that it will be unable to certify the purity of as many as 700,000 people within the time limit stipulated by the law.

看管特务机关档案的研究所正在受到人们的关切，他们难以在法律规定的时限内证明70万人的清白。

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Law enforcement agents should be able to test the toxin found in the letters to determine its potency and purity, as well as learn what chemicals may have been used to extract it from widely available castor beans, said Murray Cohen, the founder of the Atlanta-based Frontline Foundation, which trains workers on preparedness and response to bioterrorism and epidemics.

NPR: Experts: Ricin Like That In Letters Easy To Make