In both cases the urates are associated with uric acid (resulting from their partial decomposition), represented by the small spiked crystals
protruding from the spheres in the form of needle-shaped crystals. Urate of sodium occurs as the concretions known as ‘chalk stones’ in gout. But by far the most abundant kind of urates met with in abnormal urine is that known as amorphous urates, which constitute the most common variety of urinary deposits.
Urate of soda in a globular form commonly found in the urine of children.
Heintz states that they are a mixture of urate of sodium with small quantities of the urates of ammonium, lime, and magnesium. They are very frequently seen in the urine of persons in excellent health, in which, owing perhaps to too abundant or nitrogenous diet and an insufficiency of muscular exercise, being in excess, they are thrown down when the urine cools.
An excess of the amorphous urates in urine, like the presence of pus and phosphates, is indicated by the bulky precipitate more or less diffused throughout the vessel containing the urine. A very easy test will decide as to which of the three classes of substances (if only one of them be present) the precipitate belongs. The supernatant fluid being decanted from the deposit, about an equal bulk of liquor potassæ is added to the latter, when one of three results will ensue:
1. If it be pus, and become viscid, it will exhibit the qualities already mentioned under the description of that substance.
2. If phosphates, no alteration will ensue.
3. If amorphous urate, it will at once dissolve.
When amorphous urates are uniformly distributed throughout the urine they give it a milky appearance, which may sometimes lead to its being mistaken for chylous urine, or urine throughout which fatty particles of chyle are diffused. This latter doubt, however, may be easily set at rest by gently heating it. If the turbidity is owing to the urate it will disappear; if to chyle it will remain.