紫脲酸铵的化学式为NH₄C₈H₄N₅O₆或C₈H₅N₅O₆·NH₃，是紫红色的结晶粉末。

作为配位滴定指示剂，可以检测锌、锰、铜、钴、镍、钍、镧系元素和钪等。也能作为分光光度法测定钙的试剂。

Murexide (NH₄C₈H₄N₅O₆, or C₈H₅N₅O₆·NH₃), also called ammonium purpurate or MX, is the ammonium salt of purpuric acid. It may be prepared by heating alloxantin in ammonia gas to 100 °C, or by boiling uramil (5-aminobarbituric acid) with mercury oxide. W.N. Hartley found considerable difficulty in obtaining specimens of murexide sufficiently pure to give concordant results when examined by means of their absorption spectra, and consequently devised a new method of preparation for murexide. In this process alloxantin is dissolved in a large excess of boiling absolute alcohol, and dry ammonia gas is passed into the solution for about three hours. The solution is then filtered from the precipitated murexide, which is washed with absolute alcohol and dried. The salt obtained in this way is in the anhydrous state. It may also be prepared by digesting alloxan with alcoholic ammonia at about 78 °C; the purple solid so formed is easily soluble in water, and the solution produced is indistinguishable from one of murexide.