252 Dr. E. Schunck on the Substances discovered in 



22 eqs. Carbon 

 13 ... Hydrogen 

 9 ... Oxygen 



2712-2 100-00 

 It will be seen that the numbers of almost all of the above 

 analyses closely correspond with those of the calculated com- 

 position of lecanoric aether. There is therefore at present 

 nothing to oppose the hypothesis that pseudo-erythrine, ery- 

 thric aether, and the orsellic aethers, are all identical with leca- 

 noric aether*. 



If this conclusion be accepted, it follows necessarily that 

 erythrine, erythryline, erythric acid, and the two orsellic acids, 

 must contain lecanoric acid ; and not only the elements of that 

 acid, but the acid as such. For if by acting on a certain sub- 

 stance with boiling.alcohol we obtain the aether of a certain 

 acid, it follows that this acid must have been contained in the 

 original substance as such; since it would be contrary to all 

 analogy to suppose that boiling alcohol is capable of exerting 

 such a powerful influence on any substance as to make the 

 elements of the latter arrange themselves in such a way as to 

 form an acid, with which the basis of the alcohol might com- 

 bine to produce an aether, the affinity of oxide of ethyle for 

 organic acids being in general so weak as to render the inter- 

 vention of a strong acid necessary to cause the decomposition 

 of the alcohol before the combination can take place. 



Having now obtained a basis for comparing the various 

 colour-giving substances of the Roccclla tinctoria^ I shall in 

 the first place proceed to the consideration of erythric acid. 



* I have supposed that the formula given above for lecanoric acid, viz. 

 C 18 H 8 8 , is firmly established, and I am not aware that any experiments 

 have been made tending to establish a better. Mr. Stenhonse, however, 

 in a recent paper on Alpha-orcine and Beta-orcine (Phil. Mag., vol. xxxiii. 

 p. 1), has given a new formula for orcine, called by him alpha-orcine, viz. 

 C 2 i Hj 5 - Og. Dry orcine, according to him, is p» H 12 O c . This change he 

 has made apparently in order to obtain a formula corresponding with the 

 analyses of dry orcine; since the composition of crystallized orcine, as de- 

 termined by him, agrees much better with the old formula C lf , H n 7 than 

 with the new one. I have myself never been able to obtain dry orcine of 

 uniform composition ; and even if obtained of uniform composition, as 

 stated by Mr. Stenhouse, it may be questioned whether it is not a mixture 

 of various hydrates in some proportion determined by the temperature and 

 the length of time occupied in drying. At all events, if we change the for- 

 mula for orcine, the formula for lecanoric acid must also necessarily be 

 changed, since lecanoric acid minus carbonic acid plus water is orcine. It 

 will, however, be found impossible to find a formula which will express the 

 composition of lecanoric acid, and will at the same time be in accordance 

 with Mr. Stenhouse's new formula for orcine. I therefore prefer retaining 

 the old formulae for orcine and lecanoric acid, the more so as these also 

 harmonise with those of lecanoric sether and orceine. 



