Sentence:  Potash was scarce because of the Napoleonic Wars (1803–1815), and Bernard Courtois had resorted to <WSD>varec</WSD> imported from the Brittany and Normandy seacoasts [5]. 
Meaning of the word marked with <WSD> tags:  The calcined ash of coarse seaweed, used for the manufacture of soda and iodine.