Intelligence and Miscellaneous Articles. 235 



in the salts of silver, which contains 70' 62 per cent, of the oxide ; 

 when treated with ammonia it is converted into oxaluric acid. 



It is formed by the decomposition of 1 eq. of uric acid, which, by 

 the addition of 2 eq. of water and 4 eq. oxygen from the nitric acid, 

 is resolved into 2 eq. carbonic acid, 1 eq. parbanic acid, and 1 eq. 

 urea ; the latter is decomposed as before-mentioned by the hyponi- 

 trous acid. One eq. alloxan with 2 eq. oxygen is solved into 2 eq. 

 carbonic acid, 4 eq. water, and 1 eq. parabanic acid. 



The formula of the crystalline acid is CgN204 + 2 aq. 



OXALURIC ACID. 



Discovered by Wohler and Liebig. Produced by the decompo- 

 sition of parabanic acid. Prepared by adding dilute sulphuric or 

 hydrochloric acid to a saturated solution of oxalurate of ammonia 

 in hot water, and rapidly cooling the mixture when the oxaluric 

 acid falls as a white crystallhie powder ; this should be washed with 

 cold water as long as the washing, when neutralized by ammonia, 

 causes with the salts of lime a precipitate which is perfectly redis- 

 solved by heat, or by an additional quantity of water. It is a white, 

 or slightly yeUow crystalline powder of an acid taste, reddens the 

 vegetable colours, and, when neutralized by ammonia, forms with 

 silver salts a white precipitate which is perfectly redissolved by 

 boiling. By boiling in water it is completely decomposed into free 

 oxalic acid and oxalate of urea. The oxaluric acid is formed by the 

 addition of 2 eq. water to the constituents of the parabanic acid. 

 It contains further the elements of 2 equivalents of oxalic acid and 

 1 eq. urea ; it may be considered as uric acid in which the cyan- 

 oxalic acid has been replaced by the oxalic acid. 



Its formula is CgNoHjO^ + aq. 



Oxalurate of Ammonia. — This salt maybe formed by heating a 

 solution of parabanic acid with ammonia, or more advantageously 

 by treating a recently prepared solution of uric acid in dilute nitric 

 acid with an excess of ammonia and evaporating. The liquid ac- 

 quires at first a purple colour, which disappears during the evapo- 

 ration, and if allowed to cool when arrived at a certain deo-ree of 

 concentration, it deposits radiated groups of hard acicular yellow 

 crystals ; they are obtained colourless by charcoal and recrystal- 

 lization. 



The oxalurate of ammonia crystallizes in radiated groups of fine 

 acicular crystals, which have a silky lustre, and are readily dissolved 

 by hot, but with difficulty by cold water ; the solution has no re- 

 action on vegetable colours, and may be boiled and evaporated with- 

 out change ; the dry salt loses no weight at 250°, but at a higher 

 temperature it is decomposed with the rapid evolution of hydrocya- 

 nic acid. Acids separate from a concentrated solution the oxaluric 

 acid as a crystalline powder. 



Its formula is NH^O-f-CfiNoHgO,. 



OXALURIC ACID AND METALLIC OXIDES. 

 The oxaluric acid forms with the alkalies very soluble, but with 



