OF ARTS AND SCIENCES. 259 



To determine the solubility in cold water a hot solution was kept 

 at 20° for four hours with occasional stirring. The solution was then 

 filtered into weighed platinum crucibles, evaporated to dryness, and 

 the residue heated at 160°. 



I. 35.6147 gr. solution left 0.0189 gr. residue. 



II. 25.2221 gr. solution left 0.0134 gr. residue. 



III. 21.92G0 gr. solution left 0.0116 gr. residue. 



The solution saturated at 20° contained in percentages: — 



l. 2. 3. 



0.0531 0.0532 0.0529 



Taking the mean of these results dimethyluric acid requires for 

 solution 195.2 parts boiling water and 1885.3 parts of water at 20°. 



An aqueous solution has a slight acid reaction, and decomposes 

 carbonates on heating. A solution in sodic or potassic hydrate is not 

 precipitated by carbonic dioxide. From concentrated cold solutions it 

 is precipitated by stronger acids in a gelatinous form ; from more 

 dilute solutions it separates in crystals. 



Salts of Dimethyluric Acid. 



Dipotassic dimethyhirate. 

 K 2 C.(CH 3 ) 2 N 4 3 . 4 11,0. 



Dimethyluric acid was dissolved in an excess of a dilute solution 

 of potassic hydrate, the clear solution boiled for several minutes, and 

 about ten volumes of alcohol added. The crystalline precipitate, 

 which separated on standing, was filtered off rapidly by the pump, 

 washed with alcohol, and dried in vacuo over sulphuric acid and po- 

 tassic hydrate. This salt crystallizes in fine silky needles, which are 

 very soluble in water. It absorbs carbonic dioxide very rapidly from 

 the air, probably forming the monopotassic salt. 



To determine the water of crystallization the salt was heated in a 

 current of dry air, free from carbonic dioxide. 



0.8079 gr. salt dried in vacuo gave 0.1662 gr. H,0 = 20.57% 



Calculated for K 2 a(CH 3 ) 2 N,0 3 . 4 H 2 . .". 20.92% 



0.3198 gr. anhydrous salt gave 0.1766 gr. KC1 . K = 28.95$ 



Calculated for K 2 C 6 (CIL) 2 N,0 3 28.73% 



