Human folly for 02020-09-25

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• Basics ion exchange (theskepticalchemist.com):

  how ion exchange resin #materials work for purification

• Collections iron how did they make it part II trees for blooms (acoup.blog):

  #economics of pre-modern bloomery smelting of #iron; on the order of two man-days of work, largely charcoal-burning, per kg of iron. #history