156 BASIC BODIES. 



doubted. We know with certainty only three salts of urea, namely, 

 the hydrochlorate, the nitrate, and the oxalate. 



Hydrochlorate of urea, C 2 H 4 N 2 O 2 .HC1, was simultaneously 

 obtained by Erdmann* and Pelouzef. They prepared it by passing 

 a stream of dry hydrochloric acid gas over urea. The compound is 

 white and hard, and crystallises in plates ; it attracts water from the 

 atmosphere, arid from this water the hydrochloric acid escapes by 

 evaporation, and pure urea crystallises ; in water the salt becomes 

 rapidly decomposed into hydrochloric acid and urea. 



Nitrate of urea, C 2 H 4 N 2 O 2 .HO.NO 5 (according to the analysis 

 of Regnault, which has been repeated by MarchandJ, Heintz, 

 Fehling,|| and Werther,^[) is formed by mixing a concentrated 

 solution of urea with an excess of nitric acid ; the compound at 

 once separates (on cooling, almost perfectly,) in large nacreous, 

 shining scales, or in small, glistening, white plates ; on examining 

 under the microscope the contact of the urea and the nitric acid, 

 we first observe very obtuse rhombic octohedra, at whose acute 

 angles ( 82) more particles are gradually accumulated, so that 

 they appear to increase in size, and the octohedra become 

 converted into rhombic tablets, or form hexagonal tablets (whose 

 opposite acute angles likewise are 82) ; these crystals always occur 

 isolated, or in uniformly superimposed masses (C. Schmidt**). 

 This salt is uninfluenced by the atmosphere, has an acid taste, is 

 more soluble in pure water than in water containing nitric acid, 

 and dissolves in alcohol, producing considerable depression of 

 temperature ; on evaporating its aqueous solution, the salt very 

 readily effloresces ; it reddens litmus ; a concentrated solution is 

 not affected by boiling, but a dilute solution is converted into 

 carbonic acid, carbonate of ammonia, water, and nitrous oxide 

 (C 2 H 4 N 2 2 .HO.N0 5 =H 3 N + 2C0 2 + 2HO + 2NO). On heating 

 dried nitrate of urea rapidly, it decrepitates, but on heating it slowly 

 to 140, it becomes decomposed into carbonic acid, nitrous oxide, 

 urea, and nitrate of ammonia. If the solution of this salt be not 

 too dilute, a solution of oxalic acid precipitates oxalate of urea. 

 Oxalate of urea, C 2 H 4 N 2 O 2 .HO.C 2 O 3 (sometimes, according to 



* Journ. f. pr. Ch. Bd. 25, S. 506. 



* Ann. de Ch. et de Phys. 3 Sdr. T. 6, p. 63. 



t Journ. f. pr. Ch. Bd. 35, S. 481. 



Pogg. Ann. Bd. 66, S. 114-122. 



|| Ann. d. Ch. u. Pharm. Bd. 55, S. 249. 



11 Journ. f. pr. Ch. Bd. 35, S. 51-66. 



** Entwurf u. s. w. S. 42-45. 



