266 [Recess. 



The following is a comparison of theory and experiment : 

 Erythro- Theory. Experiment. 



C 8 =48 .... 39'35 39-35 



H 10 = 10 .... 8-19 8-74 



O s =64 .... 52-46 



122 100-00 



As therefore the ether produced from two different sources, 

 namely, from erythrin and alpha-orsellic acid, when boiled with 

 alkalies yields erythroglucine, I think there is every reason to expect 

 that the ethers derived from lecanoric and other lichen acids, when 

 similarly treated, will likewise yield orcin and erythroglucine, thus 

 affording still further confirmation of the correctness of Dr. Schunck's 

 hypothesis. It now naturally occurred to me to treat the methylic 

 ether obtained from alpha-orsellic acid with lime, in order either to 

 procure a homologue of erythroglucine, or to attain results which 

 might throw some light on the constitution of erythroglucine itself. 

 The result of this experiment was somewhat unexpected ; for though 

 several trials were made on a considerable scale, and the boiling with 

 lime was continued, as before, till the ether was entirely decomposed, 

 much orcin but no erythroglucine was produced. The same negative 

 results were obtained when the methylic ether prepared from erythrin 

 was subjected to a similar treatment. It appears therefore that 

 ethyl is necessary to the formation of erythroglucine from alpha- 

 orsellic acid, and that it cannot be replaced by methyl. 



From the very great analogy which erythroglucine bears to 

 ordinary mannite (being, in fact, the mannite of the lichen series), I 

 was induced to submit it to the action of hydriodic acid, in precisely 

 the same way adopted by Wanklyn and Erlenmeyer with mannite. 

 A considerable quantity of erythroglucine was introduced into a retort 

 and distilled with a great excess of strong hydriodic acid, while a 

 current of carbonic acid gas traversed the hot liquid. A dark- 

 coloured oil of an ethereal odour, and heavier than water, mingled 

 with abundance of free iodine, passed over into the receiver, while a 

 large quantity of a black humus-like body remained in the retort. The 

 latter substance was evidently an organic compound containing much 

 iodine ; but as it was insoluble in all the usual solvents, such as 



