Purpurate of Soda is of a dark brick-red colour, and may be obtained in crystals; it is much leas soluble iu water than the potash salt, requiring 3000 times its weight for solution, or even more at 60% The purpurates of baryta, and strostia are still less soluble than those above described; they are of a deep greenish colour, but when dissolved in water they impart a purple colour to it. There are two salts of lime ; one of which is a bulky red crystalline powder, and the other, which is grecuish-black, appears to be a eubsalt. The purpurate of magnesia is very soluble.
When purpurate of ammonia is added to a solution of metallic salts, the effects produced are as follows :—Cobalt, a granular reddish precipitate; sine, a fine yellow ; tin, a scarlet precipitate ; mercury, protosalts, a purple precipitate ; pensalta, a pale rose precipitate ; silver, a deep purple one; the salts of lead, iron, nickel, and copper, the chlorides of gold and platina, alter their colour by the addition of purpurate of ammonia, but are not precipitated by it. The pink sediment which generally appears in the urine of those Labouring under febrile affec tions, appears to owe its colour to the purpurate of ammonia.
Allamtoin allantoic or amniotic acid. A product of the oxidation of uric acid by peroxide of lead in a boiling solution ; the hot filtered solution deposita colourless brilliant crystals of allantoin. Allantoin also occurs in the urine of the foetal calf, and in the allantoic fluid of the cow. It Is a neutral body, tasteless, inodorous, tolerably soluble fn boiling water, but only slightly so in cold water. Left in contact with strong caustic potash for a few days it appears to assimi late two equivalents of water and become hydantoic add (C,H,N,00. Solution of allantoin, heated in a closed tube to Fehr., gives white deliquescent allanturic acid (110,C,X.N.0,) insoluble in alcohol. Lantanuric acid, a product of the action of forrocyanide of potassium upon uric acid, is probably identical with allanturic acid.
Xanthic, or uric oxide or urous acid, forms the chief constituent of a rare form of urinary calculus. It is also contained in the intestinal concretions of animals or BEZOARS. It is soluble in alkalies, but is reprecipitated as a white powder by acids, and is insoluble in water, alcohol, or ether.