1876.] Messrs. Stenlioiise and Groves on Picrorocellin. 63 



stance may be more conveniently prepared, however, by the action of dilute 

 acids on picrorocellin, the proportions which gave the most satisfactory 

 results being 1 part of picrorocellin to 4 of strong hydrochloric acid and 

 4 of water. The mixture was boiled for about 8 hours in a flask furnished 

 with a return condenser, and the product, which still contained some un- 

 altered picrorocellin, was collected, washed, and dissolved in boiling spirit. 

 On cooling, the xanthorocellin was deposited in slender needles of a pale 

 yellow colour, which amounted to about 70 per cent, of the picrorocellin 

 originally employed. They were easily purified by U\o or three crystal- 

 lizations from boiling spirit. When dilute sulphuric acid was substituted 

 for the hydrochloric acid, the results obtained were not so good, oily im- 

 purities seeming to be formed at the same time. The compound as pre- 

 pared by this process is identical with that obtained when picrorocellin is 

 subjected to a temperature of 220° in the manner previously described, 

 both substances melting at 183°. 



Although xanthorocellin could be prepared with tolerable facility by 

 the action of dilute hydrochloric acid on picrorocellin, yet it had the dis- 

 advantage that a portion of the latter always remained unattacked ; this 

 w^as due, no doubt, to its insolubility in the dilute acid. It seemed pos- 

 sible that this inconvenience might be obviated by employiug an alcoholic 

 solution of picrorocellin. On makiug the experiment, it was found that 

 when an alcoholic solution of the substance was acidulated with hydro- 

 chloric acid and boiled, although xanthorocellin was readily formed, yet in 

 order to recover it, it was necessary to partly distil off the spirit and theu 

 precipitate with water ; the product was in this case accompanied with 

 more or less of a tarry matter. These difliculties, however, were over- 

 come by the use of glacial acetic acid. Picrorocellin dissolved readily in 

 the boihng acid, and if sufficiently concentrated crystallized out again un- 

 changed on cooling. On adding a drop of hydrochloric acid to the hot 

 colourless solution and again boiling it, it almost instantly became of a 

 yellow colour, and now no longer deposited crystals of picrorocellin when 

 cooled. The addition of water to this solution immediately produced a 

 precipitate of xanthorocellin. 



After numerous trials, the following was found to be the best method 

 of preparing xanthorocellin : — 10 grams of picroroceUin are dissolved in 

 15 grams of boiling glacial acetic acid, 6 drops of concentrated hydro- 

 chloric acid are added and the whole boiled for 15 minutes in a flask 

 furnished with an inverted condenser. On allowing it to stand for some 

 time after it has become cold, it solidifies to a mass of crystals of the 

 xanthorocellin. These are stirred up with water, thoroughly washed to 

 remove adhering acid, and then recrystallized from spirit. The yield in 

 this case was found to be 76 per cent, of the picrorocellin employed, and 

 the alcoholic mother liquors when evaporated left neither tarry residue 

 nor undecomposed picrorocellin. "When dilute sulphuric acid was sub- 

 stituted for the hydrochloric acid in this experiment, the result was very 



