CHLOROPHYLL AND THE CHLOROPLASTS 375 



of reforming carbonic acid and chlorophyll. Some evidence is presented 

 which supports this conclusion and it would be highly desirable to have 

 further investigation of this point. Willstatter and StoU showed thai 

 when a colloidal solution of chlorophyll has been allowed to absorb car- 

 bon dioxide (the reaction not having gone far enough to liberate mag- 

 nesium), the gas thus absorbed and the chlorophyll can be recovered by 

 adding the chlorophyll-carbonic acid solution to alcohol at 0°. It was 

 shown that in this process the chlorophyll had lost no magnesium. 



Willstatter and Stoll have shown that when chlorophyll is treated with 

 weak acids both bonds of magnesium to nitrogen are broken. They sug- 

 gest that in the chlorophyll-carbonic acid addition product only one of 

 these bonds is broken and a primary magnesium compound of phaeophytin 

 is formed. The following formulae, in abbreviated form, illustrate the 

 hypothetical reaction of the magnesium and carbonic acid : 



I II 11 



c c c — 



^"^ /\ / 

 \ / \ / V 



"~~~;=^ig + C02+H20 ^ 



,. "" I 

 N ."'" C N 



/\ /\ /\ 



V V >- 



I II II 



Chlorophyll 



'"-;>^ig-o-c{ 



N,-'" C N 



c c c— 



I II 11 



Chlorophyll-carbonic acid 



The hypothetical chlorophyll-carbonic acid may break down in either of 

 two wavs : 1, by a reversal of the above reaction into chlorophyll and 

 carbonic acid (in alcoholic solution) and 2, in water solution, into phaso- 



