1876.] Messrs. Steiihouse and Groves on Picrorocellin. 61 



than that obtained from the lichen which has been exhausted with milk 

 of lime. The erythrin in this lichen is identical with that from the ordi- 

 nary kinds of R. fuciformis, yielding orcin and erj^thrite when boiled 

 with lime or other alkalies. 



The nearly colourless substance was now boiled for some time with about 

 ten times its weight of spirit, and filtered whilst hot through a vacuum 

 filter. In this operation it is necessary to use a hot-water funnel, as, 

 otherwise, the crystals which separate soon choke up the filter. The 

 filtered solution, which should be boiled until clear, on cooling, deposits a 

 large amount of crystals, which evidently consist of a mixture of two 

 substances, one forming lustrous'prisms, the other feathery tufts of minute 

 flattened needles. These two substances can be easily separated mechani- 

 cally by elutriation, the comparatively large prisms of picrorocellin, from 

 their size and weight, rapidly sinking to the bottom of the solution, whilst 

 the light feathery tufts of the other compound remain suspended. One 

 or two recrystaliizations from spirit generally suffice to purify the former ; 

 but if they have any green tinge, it is necessary to treat them previously 

 with boiling benzine in order to remove the trace of chlorophyl to which 

 the colour is due. 



The new compound crystallizes in long prismatic crystals of considerable 

 lustre, which are moderately soluble in boiliug spirit, slightly soluble in 

 ether and benzine, but; almost insoluble in water, petroleum, and carbon 

 bisulphide. It melts at 192°-194° C, and when more strongly heated 

 boils and gives off vapours of an oily substance of a pleasant aromatic 

 odour, leaving a small amount of carbonaceous residue. Cold concentrated 

 sulphuric acid colours it of a deep brown ; but when it is warmed it dis- 

 solves, forming a pale yellow solution, from which water precipitates a 

 yellow compound. If the sulphuric acid solution be heated nearly to its 

 boiling-point, it darkens and gives off sulphurous anhydride ; the addition 

 of water then gives no precipitate. It is also soluble in warm nitric acid, 

 and the addition of water causes a yellow precipitate similar in appearance 

 to that produced in the sulphuric acid solution ; the nitric acid solution, 

 when heated, gives off nitrous fumes. If boiled with dilute sulphuric or 

 hydrochloric acid for a short time, the picrorocellin is decomposed, a com- 

 pound, ocantliorocellin, being formed which crystallizes from alcohol in long 

 silky needles of a pale yellow colour. When picrorocellin is distilled with 

 a mixture of dilute sulphuric acid and potassium dichromate, it is de- 

 composed, an oil passing over having the odour of benzoic aldehyde, ac- 

 companied by a white crystalline substance. The latter, after being 

 purified by recr3^stallization, melted at 121° and had the general appearance 

 and properties of benzoic acid, with which it is identical. It was also 

 found to be oxidized by an acid solution of potassium permanganate, but 

 no odour of bitter-almond oil was observable. 



The substance dried at 100° was submitted to analysis, with the fol- 

 lowing results : — 



