Grimaux by heating one part of glyoxylic acid with two parts of urea for ten hours at ioo° C.: 2CO(NH 2) 2 + CH(OH) 2 Oooh = 3h 2 O + C4H6N403.
It is reduced by sodium amalgam to glycouril C 4 H 6 N 4 O 2, whilst with hydriodic acid it yields urea and hydantoin C 3 H 4 N 2 O 2.
By using urea, guanidine, thiourea and related compounds instead of amidines, one obtains the uracils.
Uracil and its homologues may be obtained in many cases from the hydrouracils by the action of bromine, and subsequent elimination of the elements of hydrobromic acid; or by the condensation of aceto-acetic ester and related substances with urea, thiourea, guanidine, &c. Uracil, C4H402N2, crystallizes in colourless needles, is soluble in hot water and melts with decomposition at 335° C. Hydrouracil, C4H602N2, is obtained by the action of bromine and caustic alkalis on succinamide (H.
Roithner, Monats., 1896, 17, p. 172); by the fusion of 0-aminopropionic acid with urea; by the electrolytic reduction of barbituric acid (J.
Tafel, Ber., 1900, 33, p. 3385), and by the condensation of acrylic acid with urea at 210-220° C. (E.
On oxidation with potassium permanganate it is converted into acetyl urea, together with other products.
It may also be obtained by oxidizing allylene and propylene with cold potassium permanganate solution, by the hydrolysis of barbituric acid (malonyl urea) with alkalis (A.
Carbon bisulphide combines with primary amines to form alkyl dithiocarbamates, which when heated lose sulphuretted hydrogen and leave a residue of a dialkyl thio-urea, CS 2 +2R NH 2 - R NH CSS NH 3 RCS(NHR)2+H2S; or if the aqueous solution of the dithiocarbamate be boiled with mercuric chloride or silver nitrate solution, a mustard oil (q.v.) is formed, R.NH CSS NH3R+HgC12-Hg(R NH CSS)2->2RNCS-}-HgS+H2S.
This dogma was shaken by Wohler's synthesis of urea in 1828.
But the belief died hard; the synthesis of urea remained isolated for many years; and many explanations were attempted by the vitalists (as, for instance, that urea was halfway between the inorganic and organic kingdoms, or that the carbon, from which it was obtained, retained the essentials of this hypothetical vital force), but only to succumb at a later date to the indubitable fact that the same laws of chemical combination prevail in both the animate and inanimate kingdoms, and that the artificial or laboratory synthesis of any substance, either inorganic or organic, is but a question of time, once its constitution is determined.'.
Salicylic acid and salicin (q.v.) share the properties common to the group of aromatic acids, which, as a group, are antiseptic without being toxic to man - a property practically unique; are unstable in the body; are antipyretic and analgesic; and diminish the excretion of urea by the kidneys.
It was first prepared by C. Scheele and is formed when urea HO C< N C-OH is strongly heated or when cyanuric chloride > N is treated with water.
The diketotetrahydrotriazoles, or urazoles, are formed by condensing urea derivatives with hydrazine salts, urazole itself resulting by the action of urea or biuret on hydrazine or its salts.
CYANAMIDE, NC NH 2j the amide of normal cyanic acid, obtained by the action of ammonia on cyanogen chloride, bromide or iodide, or by the desulphurization of thio-urea with, mercuric oxide; it is generally prepared by the latter process.
The urea in urine is also rapidly converted by the uro-bacteria into ammonium carbonate.
On the latter they act as diuretics, but less powerfully than potassium, increasing the flow of water and the output of urea and rendering the urine less acid.
ALLOXAN, or Mesoxalyl Urea, C 4 H 2 N 2 0 4 or CO NCO an oxidation product of uric acid, being NNH - CO/ obtained from it by the action of cold nitric acid, C 5 H 4 N 4 03 -}- H 2 O + 0= C4H2N204 -FCO(NH 2) 2.
Zinc and hydrochloric acid in the cold convert it into alloxantin, hydroxylamine gives nitroso-barbituric acid, C 4 H 2 N 2 0 3: NOH, baryta water gives alloxanic acid, C 4 H 4 N 2 0 5, hot dilute nitric acid oxidizes it to parabanic acid, hot potassium hydroxide solution hydrolyses it to urea and mesoxalic acid and zinc and hot hydrochloric acid convert it into dialuric acid, C4H4N204.
They combine with phenyl isocyanate to form urea derivatives (H.
With urea it gives " /CH NN quinazolone I, and with mandelic nitrile and its H /C0 homologues it forms oxazole derivatives (S.
But it was the achievement of Wailer alone, in 1828, to break down the barrier held to exist between organic and inorganic chemistry by artificially preparing urea, one of those substances which up to that time it had been thought could only be produced through the agency of "vital force."
Ethyl nitrate, C2H5.0N02, is a colourless liquid which boils at 86.3° C. It is prepared by the action of nitric acid on ethyl alcohol (some urea being added to the nitric acid, in order to destroy any nitrous acid that might be produced in secondary reactions and which, if not removed, would cause explosive decomposition of the ethyl nitrate).
When heated with urea to ioo° C. it forms allantoin.
UREA, or Carbamide, Co(NH2)2, the amide of carbonic acid, discovered in 1773 by H.
The urea oxalate is recrystallized and decolorized and finally decomposed by calcium carbonate (J.
Phys , 8, p. 235) concentrates the urine and precipitates the urea by nitric acid.
Urea crystallizes in long needles or prisms which melt at 132° C. and sublime when heated in vacuo.
Dry chlorine gas passed into melted urea decomposes it with formation of cyanuric acid and ammonium chloride, nitrogen and ammonia being simultaneously liberated.
Alkaline hypobromites or hypochlorites or nitrous acid decompose urea into carbon dioxide and nitrogen.
In this reaction urea is heated in a dry tube until it gives off ammonia freely; the residue is dissolved in water, made alkaline with caustic soda, and a drop of copper sulphate solution is added, when a fine violet-red coloration is produced.
Liebig (Ann., 18 53, 8 5, p. 289) precipitates dilute solutions of urea with a dilute standard solution of mercuric nitrate, using alkaline carbonate as indicator.
Riegler (ibid., 18 94, 33, p. 49) decomposes urea solutions by means of mercury dissolved in nitric acid, and measures the evolved gas.
Urea chlorides are formed by the action of carbonyl chloride on ammonium chloride (at 400° C.), or on salts of primary amines.
Urea chloride, NH 2 CO C1 (L.
Nitrourea, H 2 N CO NH NO 2, prepared by adding urea nitrate to wellcooled concentrated sulphuric acid (J.
Hydroxy-urea, N H2 CO NH OH, is produced from hydroxylamine and cyanic acid (W.
For example, aa-dimethyl urea is sweet, aß-dimethyl urea is tasteless; p-phenetol carbamide or dulcin, NH 2 CO NH C 6 H 4.0C 2 H 51 is sweet, while the di-p-phenetol carbamide, CO(NH C 6 H 4.0C 2 H 5) 21 is tasteless.
The derivatives of urea containing acid radicles are known as ureides.
Those derived from monobasic acids, obtained by the action of acid chlorides or anhydrides on urea, decompose on heating and do not form salts.
Acetyl urea, NH 2 CO NH 000H 31 formed by the action of acetic anhydride on urea, crystallizes in needles which melt at 212° C. and, on heating, strongly decomposes into acetamide and cyanuric acid.
Methyl acetyl urea, CH 3 NH CO NH000H 31 is formed by the action of potash on a mixture of bromine (I mol.) and acetamide (2 mols.) (A.
Bromural or a-bromisovaleryl urea, NH 2 C0 NH C0 CHBr CH(CH 3) 2, has been introduced as an hypnotic; its action is mild, and interfered with by the presence of pain, cough or delirium.
Parabanic acid (oxalyl urea), C0[NH C0] 21 is formed by oxidizing uric acid; or by condensing oxalic acid and urea in the presence of phosphorus oxychloride.
When heated with urea, it forms oxalyl diureide, H 2 N [[Coco.
Barbituric acid (malonyl urea), CH2[C0 NH]C0.2H20, formed by condensing malonic acid with urea (E.
Tartronyl urea (dialuric acid), C0[NH CO]CH OH, formed by the reduction of alloxan (J.
Allophanic acid, NH 2 C0 NH CO 2 H, is not known in the free state, as when liberated from its salts, it is decomposed into urea and carbon dioxide.
- Nh2c0 Nh C02r]]; by the action of chlorcarbonic esters on urea (H.
Schiff, Ann., 1896, 291, p. 367); and by the action of urethanes on urea chloride (L.