salt as an exemplary arrangement of the preferred embodiment u201d alternative arrangements include salt made with any other suitable counter ion such as an inorganic metal e g na k ca mg ag or an organic base the above precipitate is redissolved in distilled water in this example in 2 l of distilled water the solution is deep brown the colour can be removed by repeated circulation of solution through a carbon cartridge e g an aqua pure water filter apii at room temperature for 2 hours see step 21 in fig9 the final solution becomes light yellow in colour and is rotary evaporated to dryness considerable losses up to 30 of u201c good u201d xylan sulfate can be experienced if a carbon cartridge with low selectivity is used it is preferable to use a good grade of activated carbon powder in a batch process the amount of carbon relative to the xylan sulfate is approximately 20 weight weight referring to step 22 in fig9 the decoloured solution is filtered through a 0 45 u03bcm cellulose acetate membrane with a prefilter the filtrate is then desalted as described above e g using a millipore ultrafiltration system provided with a prep scale u2122 tff cartridge cut off mw 1000 using purified water bp the.