A description of the above process was given by T. N. Mukharji of Calcutta, who in response to a request from Sir Joseph Hooker, investigated an animal source in Monghyr, north-east Bihar, India. Mukharji identified two sources, one of mineral origin and one of animal origin. The latter was of special interest and he noted how cows were fed with mango leaves, suffered from the poor nutrition, with the sparse urine having to be collected in small pots, cooled, and then concentrated over a fire. The liquid was then filtered through cloth and the sediment collected in balls, then dried over a fire and in the sun. Importers in Europe would then wash and purify the balls, separating greenish and yellow phases. Mukharji also sent a sample to Hooker. Hooker had part of the sample examined by the chemist Carl Gräbe, who took considerable interest in its chemistry. In a 2018 publication, the analysis of part of this sample was documented. It confirms the animal origin of the sample and identifies the source as urine based on hippuric acid which is a key marker. The pigment can be clearly distinguished by spectroscopic techniques.
