418 MAEION I. NEWBIGIN. 



pterin. The association between colour and spectrum is not, 

 however, so close as in the case of chsetopterin, for the solution 

 even when only slightly acidified shows a strong tendency to 

 become green. 



When the acidified solution is diluted with water and shaken 

 with ether, the ether extracts a considerable amount of 

 pigment, more than is the case with chaetopterin, entero- 

 chlorophyll being apparently somewhat less soluble in dilute 

 acid than is chaetopterin. 



The ether is pale green in colour ; it usually displays four 

 bands, but the first band tends to be about X 657 instead of 

 A 667, as in the original solution. That is, the spectrum is 

 that of fig. 6, but the first band tends to be replaced by the 

 first band of fig. 7. When the ether is evaporated and the 

 residue dissolved in methylated spirit, a green solution is 

 formed, which turns brown and not green with acid. If 

 the ether before evaporation be placed in a separation funnel 

 and concentrated hydrochloric acid poured in, the acid becomes 

 bright deep green, and the ether remains yellowish green. 

 When examined with the spectroscope it then shows two bands 

 in the red, one at A 667, and one at about A 650 (fig. 8), which 

 in a very thick layer overlap and produce the appearance of a 

 broad band at A 657. 



It is thus obvious that acid has the same eff'ect on solutions 

 of enterochlorophyll as it has on those of chsetopterin. That 

 is, it produces small amounts of a one-banded acid derivative 

 which is not fluorescent, and is readily soluble in ether and 

 alcohol. 



It may perhaps be well to notice, in regard to the action of 

 acid on these pigments, that the statement that they differ 

 from chlorophyll in that they can be converted into the acid 

 form, and then reconverted to the normal by means of alkali any 

 number of times, is not strictly speaking accurate, for acid acts 

 on the pigment very slowly, and the " reconversion " is in the 

 general case merely due to the removal of acid from the 

 solution; in the case of the Patella pigment, indeed, the 

 normal pigment often precipitates from a dilute acid solution 



