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.

    955/1062
    much as, when heated with a large excess of potassium perman- ganate in presence of much free alkali, it gives off all its nitrogen in the free slate as gas, whereas when amides and ammonium-salts are thus treated, the whole of the nitrogen is oxidised to nitric acid. Its formation from ammonium carbamate tends to show that it is the amide of carhamic acid, and as such indeed it is regarded by Kolbe. If, however, carbamic acid be represented by the formula CO | qjj2, its amide must be identical with the diamide of car- bonic acid, that is with carbamide : thus NH, NH„ OH I' X 1 CO CO CO NHj Carbamic acid. Carbamide. Carbonic acid. It is possible, however, that the true constitution of carbamic acid C=0 may be that represented by the formula NH2 , in which the nitro- I OH gen is quinquivalent, and in that case its amide will be— C=0 II ( (CO) NH2 or *H H2 NH., (NH 2 which is perhaps the true formula of urea. A solution of pure urea shows no tendency to change by keep- ing, and is not decomposed by boiling; in the mine, on the other hand, where it is associated with putrefiable organic matter, as iuncus, the case is different. In putrid urine no urea can be found, but enough ammonium carbonate to cause brisk effer- vescence with an acid; and if urine, in a recent state, be long boiled, it gives off ammonia and carbonic acid from the same source. Orea is instantly decomposed by nitrous acid into carbon dioxide, nitrogen and water: COH4N, + 2N02H = C02 -f- 2N2 + 3H20 ; this dec position explains the use of urea in preparing nitric el her (p. 584). When chlorine gas is passed over melted urea, hydrochloric acid and nitrogen are evolved, and there remains a mixture of sal-ammoniac and cyanuric acid : (>C0H4N2 + 3C12 = 2C8H8N808 + 4NH40] + 2BEC] + N2;