Volume 1
A treatise on chemistry / by H.E. Roscoe and C. Schorlemmer.
- Henry Enfield Roscoe
- Date:
- 1877-1892
Licence: Public Domain Mark
Credit: A treatise on chemistry / by H.E. Roscoe and C. Schorlemmer. Source: Wellcome Collection.
663/792 page 647
![CARBAMIDE OR UREA. G47 ature of from 20 to 25°, and on cooling the carbamate separates out. The specific gravity of the vapour of ammonium carbamate between 37° and 100J is 0-892 (Naumann) ; hence it appears that this body is completely dissociated on evaporation into carbon dioxide and ammonia. If the gaseous mixture thus obtained be allowed to cool, ammonium carbamate is again formed, but only slowly, owing to the fact that the combination is not a direct one, but a molecular change must take place.1 When brought in contact with acids, ammonium carbamate evolves carbon dioxide, whilst with alkalis it evolves ammonia. According to Dreclisel2 a calcium carbamate, probably having the formula CO | q q2l(qH) *s Gained by mixing an alcoholic solution of the ammonium salt with a solution of chloride of calcium, and adding caustic potash. Carbamide or Urea, CO(NIT2)2. 403 Urea, which is largely contained in urine and in other liquids of the animal body, was first described in the year 1773 by H. M. Eouelle as Extradum saponaceuvi urince. It was, how- ever, more accurately investigated in the year 1790 by Fourcroy and Vauquelin. The discovery, by Wohler in the year 1828,3 that when an aqueous solution of ammonium cyanate is heated, this compound undergoes a molecular change and is converted into urea, is one of the most important discoveries of modern chemistry, inasmuch as it was the first case in which a compound formed in the animal body was prepared from its inorganic constituents:— NC(ONH4) = CO(NH2)2. Urea is also obtained by the action of ammonia on carbonyl chloride :—4 COCl2 + 2NH3= CO(NH2)2 + 2HC1. It is likewise produced by heating ammonium carbamate or common carbonate of ammonia to a temperature of from 130° to 140° (Basarow):— CO NH2 __rn f NIT ONH4 u \ Nil 2+Ho0. 2 1 Nanmaim, Ann. Chem. Pharm clx 1. 2 Ann. Chan. Pharm. clx. 7. 3 Wohler, Pogg. Ann. [1828], xii. 253.](https://iiif.wellcomecollection.org/image/b28122409_0001_0665.jp2/full/800%2C/0/default.jpg)
