The crystals of alloxantin, fig. 2, were made by adding uric acid to very dilute warm nitric acid, until no more was dissolved. The solution was evaporated at a low temperature, till it became red. Crystals were formed as the solution cooled. They were purified by re-crystallization. The parabanic acid was made by dissolving uric acid. in moderately strong nitric acid, which had been previously warmed. Crystals were obtained by allowing the solution to evaporate, and were purified by re-crystallization in water. PLATE VII. The crystals represented in Plate VII were obtained from the Urine according to the process recommended by Liebig. A quantity of Urine was neutralized by lime water and precipitated by chloride of calcium. The filtered solution, after being evaporated to a small bulk, was again filtered from the saline residue which crystallized out, and mixed with a solution of chloride of zinc, previously concentrated to a syrupy consistence. After some days had passed, numerous warty masses of a compound of chloride of zinc and creatinine, with which the creatine was mixed, separated (fig. 1). These were re-dissolved in water and crystallized. The pure crystals (fig. 2), were boiled in water with hydrated oxide of lead, and the chloride of lead and oxide of zinc separated by filtration. The solution containing the creatine and creatinine was concentrated. The crystals thus obtained were purified by re-crystallization and treated with boiling alcohol, which dissolved the creatinine, leaving the creatine behind. By purification with animal charcoal and re-crystallization, the crystals represented in figures 3 and 4 were obtained. PLATE VI. ALLOXAN, CH.NO. ALLOXANTIN, CN,H,O11+6Aq. Fig. 1. Crystals of alloxan, crystallized from an aqueous solution, obtained from uric acid. Fig. 2. Alloxantin, prepared from uric acid. Fig. 3. Parabanic acid, obtained from uric acid. |