The following experiment will give an idea of the amount of lime precipitated as phosphate. A filtered puer liquor was analysed for lime and phosphoric acid, before and after the skins were passed through. The results were, in grm. per litre-- Before After Soluble lime as CaO 0·364 0·540 P_{2}O_{5} 0·424 0·328 Increase of lime, 0·176 grm.; diminution of P_{2}O_{5}, 0·096 grm. Calculated to calcium phosphate Ca_{3}(PO_{4})_{2}, this amount of phosphoric acid has combined with 0·114 grm. CaO. Assuming that the ratio of soluble to insoluble lime is the same as given, p. 36, then the lime is distributed as follows:-- Grm. Increase of soluble CaO 0·176 " " insol. CaO 0·210 Lime as Ca_{3}(PO_{4})_{2} 0·114 Hence " " oxalate (?) 0·096 That is, of the lime precipitated, 54 per cent. is phosphate, 46 per cent. oxalate. In another puer containing before use 0·383 grm. P_{2}O_{5} per litre, only traces of phosphates were found in solution _after_ goods had been puered in the liquor, and in some analyses by Jean (39) the following figures were obtained:-- GRAMS OF PHOSPHORIC ACID PER LITRE. Fresh dung after four days’ maceration 0·082 Bate after one pack of skins 0·036 Bate after two packs of skins 0·018 Although these figures are less than those found at Trent Bridge, they confirm the fact that the soluble phosphates diminish during the bating process. The phosphates in solution thus diminish during the bating, and are found in the insoluble matter which separates out. A small portion of the lime remaining in the skins is also converted into phosphate by the action of the bate. In an experiment to determine this, a portion of the same skin was taken before and after puering. The pieces were dried, ashed, the ash dissolved in dilute nitric acid, and the phosphates precipitated by ammonium molybdate. In the skin before puering no phosphates were present, but in the skin after puering there was a small amount, though not sufficient to weigh. The action of ammonium phosphate on the lime in the skin is very small. A skin was treated with a 0·1 per cent. solution of ammonium phosphate at 100° F. for one hour. The CaO in the dry skin was estimated, and found to be-- Per cent. Before the experiment 1·93 After " " 1·45 A considerable amount of calcium phosphate was found in the skin after the experiment. Other chemical compounds existing in the puer, or formed by the action of bacteria (principally _B. coli commune_, see Chapter IV.), are indol, skatol and a number of aromatic oxyacids, principally para-oxyphenyl-propionic acid, a little para-oxyphenylacetic acid and skatol carbonic acid. In addition, tyrosin, leucin, tryptophan and mercaptans have been separated.[34]