192 M. Finck on Pyroraccmic Acid. 



of baryta removed by carbonic acid, and then the baryta com- 

 bincd with acids separated by sulphuric acid. On evaporating 

 the liquid, a yellowish-brown syrup is left, from which a cry- 

 stalline substance separates. This is recrystallizcd from aqueous 

 alcohol, dissolved in baryta-water, and again precipitated with 

 hydrochloric acid. 



Thus purified it forms a white crystalline powder, very little 

 soluble in hot or cold water, crystallizing from alcohol and ether, 

 in which it is very soluble, in white stellate crystals. It melts 

 at 287 , and sublimes without change, like benzoic acid. 



The formula of the acid is C 18 H 8 O 8 , and Finck names it Uvu 

 tinic acid ; it is isomeric with insolinic acid, but differs in its 

 solubility in ether and alcohol. Finck has investigated several 

 of the salts, of which the silver and copper salts crystallize. It 

 is a bibasic acid, and the formula of the silver salt is C 18 H 6 As:' 2 O s . 



In the mother-liquor from which uvitinic acid has been sepa- 

 rated, another acid, which does not crystallize, is contained. It 

 is a very strong acid, and unites directly with metallic oxides to 

 form neutral salts, which, however, do not crystallize. The for- 

 mula of this acid appears to be C 18 H 12 14 . Finck names it 

 uvitonic acid. 



Comparing the formulae of the three acids, 



Pvroracemic acid . . . C 18 H 12 18 , 

 Uvitonic acid .... C l8 H 12 14 , 



Uvitinic acid . . . . C 18 H 8 O 8 , 



it will be seen that the formation of the latter depends on a 

 reduction of the former ; for while one part of the pvroracemic 

 acid is oxidized to oxalic acid, another part loses oxygen and is 

 converted into the other two acids. 



According to Sinimler* a highly fluorescent solution may be 

 prepared from cane-sugar as follows. To a syrupy solution of 

 cane-sugar an equal volume of sulphuric acid is gradually added. 

 The mixture blackens, a violent reaction is set up, which results 

 in the formation of a solid mass resembling black peat. "When 

 this is somewhat cool, the mass is shaken with about ten times 

 its volume of distilled water and allowed to stand. After filtra- 

 tion a liquor is obtained which in transmitted light is quite 

 colourless, except when strongly concentrated; but viewed in 

 daylight against a black cloth, exhibits a more brilliant blue 

 even than quinine. It appears to be due to a peculiar organic 

 acid, for nhen neutralized with a base the fluorescence disappears. 



* Chemisches Central-BIatt, June 18, 1862. 



