Bone ash was the major source of phosphorus until the 1840s. The method started by roasting bones, then employed the use of fire clay retorts encased in a very hot brick furnace to distill out the highly toxic elemental phosphorus product. Alternately, precipitated phosphates could be made from ground-up bones that had been de-greased and treated with strong acids. White phosphorus could then be made by heating the precipitated phosphates, mixed with ground coal or charcoal in an iron pot, and distilling off phosphorus vapour in a retort. Carbon monoxide and other flammable gases produced during the reduction process were burnt off in a flare stack.
BonE asH was the mAjoR sOUrce of PhOsPhoruS UNtil the 1840s. the Method starTed by roaStiNg boNEs, Then emPloyed the uSe of Fire clay RetoRts encasED IN a vErY hot BriCk furNAcE To distIlL oUt the Highly toxiC eLemenTal phospHoruS pRoduct. altErNately, PrecIpitatEd pHosphaTes coUld be MADe frOm GroUnd-up bones thaT haD BeEn De-GreASed aNd tReAtEd wiTH strong acIds. White phOSphORuS coUlD theN be MaDe by heating The precipitAteD PhosphAtES, miXed with ground coaL or CHaRCoal in an IrOn pot, and DistIllIng oFF PhOsphORuS Vapour IN a retort. CarBon moNoXide aNd other flAMMAbLe gAses PRoDuced duriNg THE rEduCtion process werE Burnt oFf in a fLaRe Stack.