On the Solubility of Uric Acid in Blood Serum

The solubility of uric acid in water was determined by His and Paul 1 to be about I in 39,500. Uric acid is very slightly dissociated, less than IO per cent. in saturated solution. His and Paul have, however, confined the solubility within too narrow limits. If one shakes large crystals of uric acid in water for a day at room temperature, one cannot reach a solubility of I in 40,000; if, however, one triturates a fine powder of uric acid in water for several hours, one can obtain a solubility of I in 35,ooo. This is simply a repetition of the familiar experience of the physical chemists in the preparation of saturated solutions of calcium sulphate for purposes of standardization. I am acquainted with no published researches in which the solubility of uric acid in the body fluids has been determined with methods of precision. It has been long recognized that in no known disease is the blood serum saturated with uric acid. Even in those specimens of blood from which uric acid will crystallize on the immersion of a thread, the solution is not saturated; this may be easily shown in the simple experiment of adding more uric acid in substance and observing that some of it will be dissolved. The assumed greater solubility of uric acid in blood as compared with water has been generally attributed to the alkaline reaction of the blood. This explanation is without foundation, since the blood is not alkaline in the real sense at all, but practically as neutral as distilled water. With the demonstration of the neutrality of the blood,2 a mass of hypotheses on