500 Mr. E. Schunck oti Lecanorm, Sfc. 



perfectly the nature of the process by which they are pro- 

 duced, it is absolutely necessary to know the exact substance 

 out of which each is in the last instance formed, the last link 

 of the chain which precedes its formation. 



Pseud e7'ythr in. 



For this substance it would be advisable to substitute 

 another name, as in this case the substance by which it is ac- 

 companied is not erythrin but lecanorin. It is contained in 

 very small quantities in the lichens that I examined. It is 

 sparingly soluble in cold water, but easily soluble in boiling 

 water, from which it crystallizes on cooling in shining plates 

 and needles. If more of the substance is taken than the boil- 

 ing water can dissolve, the part left undissolved melts and 

 collects at the bottom of the fluid in oily drops, which, on the 

 temperature falling a little below 212°, congeal and form cry- 

 stalline masses. This is a characteristic property of pseud- 

 erythrin, and one distinctly mentioned by Heeren. It is easily 

 soluble in alcohol and eether, and also in alkaline solutions. 

 It gives compounds with metallic oxides by double decom- 

 position. When dissolved in ammonia and exposed to the 

 air, it gives, like lecanorin, a red colouring matter ; but its 

 conversion into the latter is much more slowly effected than 

 that of lecanorin. When subjected to dry distillation it also 

 gives a crystalline sublimate, accompanied by a copious dis- 

 engagement of gas. When its solution in an alkali is boiled 

 or left to stand some time, it imparts carbonic acid to the 

 alkali, the decomposition being accomplished, however, with 

 much more difficulty than with lecanorin. The exact natui'e 

 of the substance left in solution after this decomposition I was 

 unable to determine, on account of the very small quantity of 

 pseuderythrin which I had at my disposal. 



The combustions which I made of this substance confirmed 

 the formula established by Liebig at the time of Heeren's in- 

 vestigation, viz. CgQ Hj2 Og. 



The fatty substance mentioned above I have examined but 

 slightly. It is soluble in alcohol, but insoluble in tether and 

 water. From an alcoholic solution it is deposited in small 

 pearly-white scales; if the solution be spontaneously evapo- 

 rated, it is obtained in small, hard, shining, transparent cry- 

 stals. It is soluble in alkalies, forming soapy solutions, and 

 is re-precipitated by acids. Its alkaline solutions do not be- 

 come coloured when exposed to the air. It cannot be melted 

 without being decomposed. 



