UREA. 195 



other fluids, such as the secretion from the stomach, the 

 serous fluids, etc. 



In connection with the chemical properties of urea, it is 

 interesting to note that it is one of the few organic proxi- 

 mate principles that can be produced synthetically in the 

 laboratory of the chemist. 1 As early as 1828, Wohler ob- 

 tained urea by adding sulphate of ammonia to a solution of 

 cyan ate of potassa. 3 The products of this combination are 

 sulphate of potassa, with cyanic acid and ammonia in a form 

 to constitute urea. The cyanate of ammonia is isomeric with 

 urea, and the change is effected by a simple rearrangement 

 of its elements, the formula being NH^OjC^O (cyanate of 

 ammonia), equivalent to C 3 H 4 ]N' a O 3 (urea). It has long been 

 known that urea, in contact with certain animal substances, 

 is readily convertible into carbonate of ammonia. This trans- 

 formation is theoretically accomplished by adding to urea four 

 atoms of water. C 3 H 4 N 3 O, (urea) + 4 HO = 2 (KH 4 O,CO 2 ). 

 It has recently been stated by Kolbe, that when carbonate of 

 ammonia is heated in sealed tubes to the temperature at which 

 urea commences to decompose, it is converted into urea. 3 The 

 decomposition of urea resulting in the carbonate of ammonia 

 may be easily effected by various chemical means. As this 

 occurs in the spontaneous decomposition of urea in the urine 

 and elsewhere, it has been supposed that the symptoms of 

 blood-poisoning following retention of the urinary constit- 

 uents, in cases of disease of the kidneys, are due to the 

 decomposition of the urea into carbonate of ammonia, and 

 not to the presence of the urea itself in the blood. Many 

 interesting experiments and observations have been made 

 upon this subject, but it is now pretty generally admitted 



1 It is interesting, also, in this connection to refer to the synthesis of another 

 of the organic proximate principles ; viz., neurine, which has lately been accom- 

 plished by Wurtz (Comptes rendus, Paris, 1868, tome Ixv., p. 1015). 



2 WOHLER, Sur la formation artificielle de Vuree. Annales de chlmie et de 

 physique, Paris, 1828, tome xxxvii., p. 330. 



3 Journal of Anatomy and Physiology, Cambridge and London, 1868, vol. ii., 

 p. 430. 



