204 CONJUGATED ACIDS. 



decomposed at 170; it attracts water from the atmosphere,, and 

 thus becomes decomposed into its proximate constituents in the 

 same manner as if water were added to it. 



Products of its metamorphosis. The products of decomposition 

 of uric acid are of extreme interest, insomuch as they afford us a 

 deep and general insight into the various transpositions of atoms 

 and atomic groups. 



Alloxan, erythric acid, C 8 H 4 N 2 O 10 , is produced when 1 part of 

 dry uric acid is gradually introduced into 4 parts of nitric acid of 

 1.42 to 1.53 specific gravity, when the whole finally solidifies and 

 becomes crystalline. A better method of preparing this body is by 

 mixing 4 parts of uric acid with 8 parts of moderately strong 

 hydrochloric acid, and then gradually introducing 1 part of chlorate 

 of potash into the fluid ; in the latter case, urea and alloxan are 

 formed without any development of gas, while in the former case, 

 nitrogen and carbonic acid are evolved in consequence of the decom- 

 position of the urea by nitrous acid. (Compare p. 154.) 



Alloxan crystallises in large colourless rhombic octohedra (which 

 at first have a diamond-like lustre, but soon effloresce) with 

 6 atoms of water of crystallisation from hot but not perfectly 

 saturated solutions ; while from saturated solutions it crystallises 

 in anhydrous four-sided prisms: it has a faintly saline taste, a 

 sickly odour, reddens litmus, and communicates a purple red 

 colour to the skin. 



It is easy to see that in accordance with the above fiction 

 respecting urilate of urea, urilic acid assimilates 4 atoms of water 

 and 2 atoms of oxygen, and thus forms alloxan, (C 8 N 2 O 4 -f4HO 

 + 20=C 8 H 4 N 2 10 .) 



Alloxanic acid, C 4 HNO 4 .HO, is formed by digesting alloxan 

 with caustic alkalies, and by decomposing the baryta-salt by sul- 

 phuric acid. It crystallises in concentrically grouped needles, 

 which are unaffected by exposure to the atmosphere, have an acid, 

 (but subsequently leave a sweetish) taste, dissolve readily in water, 

 less in alcohol, and very slightly in ether ; this acid reddens litmus 

 strongly, decomposes carbonates and acetates, and oxidises zinc and 

 cadmium, hydrogen being at the same time developed; in an aqueous 

 solution it becomes decomposed at a temperature above 60. Its 

 alkaline salts are soluble in water and crystallisable ; its other 

 neutral salts are difficult of solution : like uric acid it has a strong 

 tendency to form acid salts, all of which are soluble (Schlieper.)* 



Alloxanic acid is produced by the abstraction of 2 atoms of 

 water from alloxan. 



* Ann. d. Ch. u. Pkarm. Bd. 55, S, 251-297. 



