Editing Haematoxylin (section)

==Extraction and purification==
[[File:Haematoxylum campechianum wood chips.jpg|thumb|upright=.75|left|'''Logwood''' (''Haematoxylum campechianum'') chips]]
Haematoxylin has been [[Chemical synthesis|synthesized]],<ref name="Morsingh and Robinson, 1970" /><ref name="Puchtler et al., 1986" /> although never in commercially viable amounts.<ref name="Dapson and Horobin, 2009" /><ref name="Cooksey, 2010" /> Historically the logwood was exported and the haematoxylin extracted in Europe. More recently extraction takes place closer to where the logwood is harvested.<ref name="Dapson et al., 2010" /> Extraction of haematoxylin from logwood on industrial scales has been accomplished in the 'French process' by boiling the wood chips or in the 'American process' with [[steam]] and pressure.<ref name="Ponting, 1973" /><ref name="Lillie, 1974" /> Once extracted, the dye can be sold as a liquid concentrate or dried and sold in a crystalline form.<ref name="Ponting, 1973" /> Modern production methods use water, [[diethyl ether|ether]] or [[ethanol|alcohol]] as a [[solvent]], at which point the extracts may be further refined to the level of purity needed.<ref name="Dapson et al., 2010" />

The commercial product may vary from batch to batch and between manufacturers<ref name="Dapson et al., 2010" /> in both the level of impurities and in the ratio of haematoxylin to haematein.<ref name="Schulte, 1991" /><ref name="Lillie, 1977" /><ref name="Marshall and horobin, 1974" /> For histologic use, this variability can affect the stain's interaction with biological tissue samples, and is therefore of concern to histologists and [[pathology|pathologists]].<ref name="Schulte, 1991" /><ref name="Lillie, 1977" /><ref name="Dapson et al., 2010" /> Haematoxylin, like other biological stains, may be certified by the [[Biological Stain Commission]], signifying that a particular batch of stain works in a standardized test, although this does not specify the dye's actual purity.<ref name="Schulte, 1991" />