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The methods in general use for the detection of indican in the urine are too well known to require recapitulation; they are qualitative and are of little or no value for clinical diagnosis; all are based on the breaking up of the indoxyl sulphate with hydrochloric acid, oxidizing the indoxyl into indigo, dissolving in chloroform, when the blue coloration obtained is utilized to estimate the excess. Errors arise in this method from a variety of causes. If the total quantity of urine passed in the twenty-four hours is small, a deep coloration may be obtained in the test tube, while the total amount may be normal; on the other hand, if the quantity for twenty-four hours is large, little or no coloration may be obtained, and yet the total quantity may be in excess of normal. Another point is the varying difficulty of breaking up the indoxyl; sometimes the mere
RICHARDSON H, WHITNEY EL. A METHOD FOR THE QUANTITATIVE ESTIMATION OF INDICAN AND INDIRUBIN IN THE URINE.. JAMA. 1898;XXX(16):920-921. doi:10.1001/jama.1898.72440680040001m