THE TECHNOLOGIST. 



[Jan. 1, 1865. 



284 



ON CHEMISTRY APPLIED TO THE ARTS. 



Uric acid 





1000 



Mucus 





0320 



Mineral salts 





18-440 





1000-000 



Water 



Horses. 



910-76 



Urea 





31-00 



Hippurate of 



potash 



4-74 



Lactate of 



do 



11-28 



Do. of sod 



a 



8-81 



Bicarbonate of potash 



15-50 



Carbonate of lime 



10-82 



Carbonate of 



nagnesia . 



4-16 



Other salts 





2-93 



1000-00 



The substances in human urine which call for special notice are urea 

 and uric acid ; in herbivorous animals, hippuric acid ; and in birds, 

 uric acicl. 



Urea is a substance crystallising in various derivative forms belong- 

 ing to the prismatic system — it is very soluble in water and alcohol, and 

 gives beautiful and well-defined salts with nitric and oxalic acids. 

 Urea, under the influence of a mucous substance secreted at the same 

 time, and wbich is easily modified into a ferment, is rapidly converted, 

 by the fixation of two atoms of water, into carbonate of ammonia, as 

 seen by this formula : — 



Urea 

 Water 



Carbonate of ammonia 



C, 2 N 2 H 4 

 2 H 2 



C, O. N„ H K 



This will explain the strong ammoniacal odour arising from urine 

 after being kept for a short time ; and, as it may be most important for 

 medical men to be able to preserve urine in its normal condition for 

 several days, I observed a few years since a most effectual method of 

 preserving it, which is merely the addition of a few drops of carbolic 

 acid immediately after the production of the urine. Urea is peculiarly 

 interesting to chemists, as it was the first organic substance which they 

 succeeded in producing artificially from mineral compounds. This 

 interesting discovery was made by Wbhler in 1820, in acting upon 

 cyanate of silver by hydrochlorate of ammonia. Since then Baron 

 Liebig has devised a more simple process, which consists in decomposing 

 cyanate of potash by sulphate of ammonia, wbich gives rise to sulpbate 

 of potash and cyanate of ammonia or urea. The average quantity of 

 urea rejected daily by an adult man is about an ounce, or 2\ per cent, 

 of the fluid itself. Although human urine docs not contain more than 

 1 per cent, of uric acid, and this generally combined "with soda, still 

 I deem it my duty to say a few words respecting it, for it is often the 



