“…aliquot was extracted to yield an ethersoluble coproporphyrin fraction in 0.15 N-HCl, and a small, ether-insoluble fraction of uroporphyrin. The latter fraction was further extracted by cyclohexanone at pH 1.5. and finally taken into 0.5 N-HCl (Dresel, Rimington and Tooth, 1956). Apart from allowing the urine to stand for 24 hours after collection, no additional steps for conversion of porphyrinogens were undertaken (Watson, de Mello, Schwartz, Hawkinson and Bossenmaier, 1951;Zondag and van Kampen, 1956).…”