A manual of elementary chemistry : theoretical and practical / by George Fownes.

  • Fownes, George, 1815-1849.
Date:
1873
Catalogue details

Licence: Public Domain Mark

Credit: A manual of elementary chemistry : theoretical and practical / by George Fownes. Source: Wellcome Collection.

    968/1062 (page 940)
    The following is a description of some of the more important compounds above enumerated: Allantoin, C4N4HG03.—This substance, which contains the elements of 2 molecules of ammonium oxalate minus 5 molecules of water [2C2(NH4)204- 5H20], is found in the allantoic liquid of the foetal calf and in the urine of the sucking calf. It is produced artificially, together with oxalic acid and urea, by boiling uric acid with iead dioxide and water: 2C5N4H403 + 06 + 5H20 = C4N4H0O3 + 2C2H204 + 2CN2H403. The liquid filtered from lead oxalate, and concentrated by evaporation, deposits on cooling crystals of allantoin, which are purified by re-solution and the use of animal charcoal. The mother-liquor, when further concentrated, yields crystals of pure urea. Allantoin forms small but brilliant prismatic crystals, transparent, colourless, tasteless, and without action on vegetable colours. It dissolves in 160 parts of cold water, and in a smaller quantity at the boiling heat. It is decomposed by boiling with nitric acid, and by oil of vitriol when concentrated and hot, being in this case resolved into ammonia, carbon dioxide, and carbon monoxide. Heated with concentrated solutions of caustic alkalis, it is decomposed into ammonia and oxalic acid. Alloxan, C4N2H204.—This is the characteristic product of the action of strong nitric acid on uric acid in the cold. It is best prepared by adding 1 part of pulverised uric acid to 3 parts of nitric acid, sp. gr. 1-45, in a shallow basin standing in cold Avater. The resulting white crystalline mass, after standing for some hours, is drained from the acid liquid in a funnel having its neck stopped with pounded glass, then dried on a porous tile, and purified by crystallisation from a small quantity of water. Alloxan crystallises by slow cooling from a hot saturated solu- tion in large efflorescent rectangular prisms containing C4N2H204 -4-4 aq.; from a solution evaporated by heat it separates in monoclinic octohedrons with truncated summits, containing C2N2H204 -+- aq. These crystals heated to 150°-160° in a stream of hydrogen give off their water, and leave anhydrous alloxan, C2N2H204. Alloxan is very soluble in water: the solution has an acid reaction, a disagreeably astringent taste, and stains the skin, after a time, red or purple. It is decomposed by alkabs, and both by oxidising and deoxidising agents: its most charac- teristic property is that of forming a deep-blue compound with a ferrous salt and an alkali. Alloxanic Acid, C4N2H405.—The barium-salt of this acid is deposited in small colourless, pearly crystals, when baryta-water is added to a solution of alloxan, heated to 60°, as long as the precipitate first produced redissolves, and the filtered solution is