UREA. 81 



liquid cools. At 61 100 parts of water dissolve only 4-37 of 

 oxalate of urea. It is still less soluble in alcohol than in water. 

 One hundred parts of alcohol of 0'833 dissolves only 1-6 of oxa- 

 late at the temperature of 61. According to the analysis of Ber- 

 zelius this salt is composed of, 



Oxalic acid, . 37-436 or 4-5 



Urea, . . . 62-564 or 7-525 



100-000 



It contains no water of crystallization. According to Berze- 

 lius this salt is capable of combining with the neutral alkaline 

 oxalates, forming double salts, which are soluble in alcohol. Lime 

 decomposes these salts in such a way that oxalate of lime preci- 

 pitates, while the urea and alkaline oxalate remain in solution. 



When cyanuric acid is boiled with a concentrated solution of 

 urea, and the solution filtered while hot, fine needles are depo- 

 sited as the solution cools. These are composed of cyanuric 

 acid and urea. The same salt is obtained when uric acid is dis- 

 tilled in a retort. It is soluble in alcohol. Nitric acid decom- 

 poses it, nitrate of urea being formed, and cyanuric acid set at 

 liberty. 



MM. Cap and Henri, by treating lactate of lime with oxalate 

 of urea, obtained lactate of urea, which crystallizes in white pris- 

 matic needles. They have extracted the same salt from urine. 

 They separated the free lactic acid from urine by an excess of 

 hydrate of zinc, and obtained lactate of urea identical with that 

 prepared by direct combination.* Urea possesses the property 

 of a base, and combines not only with nitric, oxalic, and lactic 

 acid, but also with sulphuric acid. Sulphate of urea may be ob- 

 tained by mixing 100 parts of oxalate of urea with 125 parts of 

 sulphate of lime in silky crystals, adding a little water and heat- 

 ing for an instant Add four or five volumes of alcohol, of spe- 

 cific gravity 0-843, filter and evaporate. The sulphate of urea 

 crystallizes in grains and needles ; its taste is sharp and cooling. 



Whan common salt is dissolved in urine, it crystallizes in oc- 

 tahedrons, while sal-ammoniac, under the same circumstances, 

 crystallized in cubes. This alteration in the shape of the crystals 

 is ascribed to the salts entering into combination with urea. 



* Phil. Mag. third series, xiii. 478; or Jour, de Pharm. xxv. 133. 



F 



