486 Transactions. — Chemistry and Physics. 



crystalline. Upon diluting the crude sulphuric-acid solution; 

 with water the smell of valeric acid is in each case distinctly 

 perceptible. 



The solution of either of the sulphonic acids when warmed 

 with very dilute nitric acid gives a yellow precipitate, the 

 formation of which may be used as a test for nitric acid. 



Art. XLIV. — Note on Interaction of Citric and Suljihuric 



Acids. 



By James Bee. 

 [Read before the Wellington Philosophical Society, 4th November, 1903.] 



During the preparation of aconitic acid by Hentschel's 

 method (in which citric acid is heated with a 66-per-cent. 

 sulphuric acid under a reflux condenser) it was found that 

 the yield varied very considerably according to the length 

 of time during which the acids were heated together. If the 

 reaction were carried on for too short a time unchanged 

 citric acid was left behind ; if the heating was continued for 

 twelve hours instead of six very little aconitic acid separated 

 from the mixture on cooling; and in a third experiment, in 

 which the materials were heated on a reflux apparatus for 

 twenty-four hours, no crystallization took place after cooling. 



It was found that, on pouring off the black liquid from the 

 vessel in which the reaction had taken place, a small black 

 deposit resembling charcoal was left. This turned out to be 

 undecomposed aconitic acid. Suspended in the dark liquid- 

 was a flocculent dark-brown precipitate, which was separated 

 from the liquid by straining through a lai'ge Buchner filter. 

 From this a little aconitic acid was isolated. 



The filtrate was diluted with water and extracted many 

 times with ether. The united residues were recrystallized 

 from glacial acetic acid, whereby aconitic acid was separated. 

 The mother liquors were freed from acetic acid by evaporation 

 with water, the residue taken to dryness and recrystallized 

 from chloroform and acetone. By this means a small quan- 

 tity of an acid which melted at 206° C. (uncorrected) was ob- 

 tained. Upon combustion it gave numbers agreeing accu- 

 rately with those of diconic acid, CgHjoOfi. 



Calculated for CgHioOe. Found. 



C = 50-47 per cent. ... 50-49 



H = 4-67 „ ... 4-56 



= 44-86 „ ... 44-95 



