498 Mr. E. Schunck on Lecanorin 



been formed. The same effect was brought about instanta- 

 neously when the solution was boiled. In order to observe 

 the process more clearly, I dissolved a quantity of lecanorin 

 in baryta water in the cold. The solution, on being boiled 

 or allowed to stand, deposited a great mass of pure carbonate 

 of baryta. The liquid was filtered rapidly, and the excess of 

 caustic baryta precipitated by a stream of carbonic acid : on 

 slow evaporation it yielded large prismatic crystals of a sub- 

 stance which possessed characters in every respect identical 

 with those of orcin. It had an extremely sweet taste, was ca- 

 pable of being volatilised without change and without leaving 

 any I'esidue, gave a deep blue colour when dissolved in am- 

 monia and exposed to the air, struck a blood-red colour with 

 nitric acid, and precipitated a solution of basic acetate of lead. 

 Lecanorin thus is converted by the action of alkalies into 

 orcin and carbonic acid, in the first instance, this decompo- 

 sition always preceding the formation of colouring matters. 

 The same decomposition is produced by the carbonated alka- 

 lies, by long boiling with water and by dry distillation, the 

 heavy vapour mentioned above as being produced by heating 

 lecanorin to decomposition, being vapour of orcin. 



The composition of lecanorin is expressed by the formula 

 Cjg Hg Og. The results of the combustions which I made of 

 it admit of no other interpretation. All attempts to determine 

 its atomic weight by means of combining it with metallic 

 oxides, failed. These compounds can only be prepared by 

 double decomposition ; but the facility with which lecanorin 

 is decomposed when alkalies are added to its solutions, always 

 renders the purity of the compounds formed liable to doubt. 

 The compound with oxide of silver, formed by adding nitrate 

 of silver to an alcoholic solution of lecanorin, and then pre- 

 cipitating by means of a few drops of ammonia, though it 

 changed colour but slightly in drying, gave no consistent re- 

 sults. The compound with oxide of lead, formed by preci- 

 pitating a solution of lecanorin with basic acetate of lead, was 

 so basic and its formula so unusual, that I am led to suppose 

 that one or two atoms of basic acetate of lead were precipitated 

 together with it. By decomposing, however, a weighed quan- 

 tity of lecanorin with caustic baryta, and determining the 

 quantity of carbonate of baryta formed, I obtained very accu- 

 rate results, confirming the formula Cq H4 O4, or 0,8 Hg Og, 

 for lecanorin. In regard to the composition of orcin, I have 

 been induced to replace the generally received formula for its 

 composition by a new one. Diimas's formula for anhydrous 

 orcin is C,g H7 O3, and for crystallised orcin Cjg H,2 Og, 

 which evidently cannot be brought into accordance with the 



