"Albuminous urine, on being exposed to a temperature of about 150 deg. becomes opaque, and deposites this principle in a coagulated state. The precipitate varies considerably in its appearance in different instances. Sometimes it is of a firmer character, and similar to that formed by the serum of the blood, from which, in this case, it may be supposed to be derived; at other times it is very delicate and fragile in its texture, and somewhat resembles curd, when it may be supposed to be of chylous origin. In some instances, the effects of heat upon albuminous urine are increased by the addition of nitric acid. But the most delicate test of albuminous matter in general is dilute acetic acid, and the prussiate of potash." p. 6. Dr. PROUT combats very successfully the opinion, generally entertained by chemists, that the power of healthy urine to redden litmus depends on the presence of free lithic acid.[23] That this power cannot depend upon lithic acid uncombined, is made evident to Dr. P. by its sparing solubility; it requiring, according to our author, 10,000 times its weight of water to dissolve it, or six times as much as is stated by Dr. HENRY. The reddening power of the urine is attributed by Dr. PROUT to the presence of lithate of ammonia, and superphosphate of ammonia: the former of which, contrary to what might be expected, is found capable of reddening litmus, and of remaining in solution with the latter, without decomposition. The following interesting remarks are made by Dr. PROUT on the effects of muriatic acid, in precipitating lithic acid gravel: