PLATE V.

URATE OF MAGNESIA. URATE OF LIME. URIC ACID.

The urate of magnesia represented in fig. 1, was prepared by the addition of sulphate of magnesia to a hot, saturated solution of urate of potash. After the lapse of two or three hours, a number of acicular crystals, collected in wart-like forms, were deposited. These were purified by re-solution in boiling water.

The urate of lime was formed by adding chloride of calcium to a hot solution of urate of potash. The precipitate was amorphous, but crystals were obtained by re-dissolving it in boiling water.

The square-shaped crystals of uric acid, represented in fig. 4, were made by adding hydrochloric acid to a weak solution of urate of potash.

The crystals of uric acid, represented in fig. 5, were obtained from the Urine of a young man suffering from slight indigestion, but otherwise in perfect health.

PLATE VI.

The crystals of alloxan, represented in fig. 1, were prepared as follows: 12 parts of uric acid were added to 17 parts of nitric acid, sp. gr. 1.412. After standing from 12 to 24 hours, crystals separated. These were purified by being re-dissolved in tepid water, and the solution concentrated by evaporation at a gentle heat, so that crystals might form.

E

PLATE V.

URATE OF MAGNESIA, CNH.Mg 0,+6Aq. URATE OF LIME, CN,H,CaO,+2Aq. URIC ACID, CH ̧ÑO

Fig. 1. Urate of magnesia crystallized in tufts.

Fig. 2. Urate of magnesia, showing the separate form of the crystals.

Fig. 3. Urate of lime, crystallized in tufts composed of very long acicular crystals.

Fig. 4. Uric acid, precipitated by the addition of hydrochloric acid to urate of potash.

Fig. 5. Uric acid deposited from Urine.

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.