=Decomposition of the Chlorophylls by Alkalies.=--The first action of dilute alkalies on the chlorophylls is to split off, by hydrolysis, the alcoholic groups of the esters, producing the crystalline tri-basic acids, or _chlorophyllins a_ and _b_. Each of these chlorophyllins exists in two forms, the normal and the iso, in which the attachment of the COOH groups to the other groups in the molecule is in different positions. Hence, chlorophyll _a_ yields chlorophyllin _a_ and isochlorophyllin _a_, and chlorophyll _b_ yields chlorophyllin _b_ and isochlorophyllin _b_, all four of which are tri-basic acids. These compounds, when heated with alkalies, split off carbon dioxide in successive stages, losing one COOH group at each step, thus yielding a series of simpler compounds of the following types: First, di-basic acids; second, monobasic acids; and finally, _ætiophyllin_, a compound in which no COOH group is present. In all of these compounds, derived from chlorophylls by the action of alkalies, the Mg remains in the molecule, and all the Mg-containing derivatives from the chlorophylls are known as "phyllins." At the stage at which only one COOH group remains in the molecule, only one group arrangement is possible, and the derivatives from chlorophyllin _a_ and isochlorophyllin _b_, and those from chlorophyllin _b_ and isochlorophyllin _a_, are identical. At the final stage, the derivatives from all four forms are identical. This may be graphically illustrated by the following diagram indicating the progressive decomposition of the two chlorophylls under the action of alkalies: [Illustration: Decomposition of Chlorophyll a and Chlorophyll b] =Decomposition of Chlorophylls by Acids.=--The first action of dilute acids upon chlorophylls is to remove the magnesium, without otherwise changing the molecule. Two hydrogens go in in the place of the magnesium. Dilute acids act in precisely the same way upon each of the "phyllins" shown in the above scheme. In this way, a whole series of compounds, corresponding to each of the chlorophylls and their alkali-decomposition products, but with the magnesium lacking in each case, has been prepared. Thus, COO·C_{20}H_{39} / Chlorophyll _a_, MgC_{31}H_{29}N_{3}-COO·CH_{3}, \\ (NHCO) COO·C_{20}H_{39} / becomes Phæophytin _a_, C_{31}H_{31}N_{3}-COO·CH_{3}, \\ (NHCO) COO·C_{20}H_{39} / Chlorophyll _b_, MgC_{31}H_{29}O_{2}N_{4} \ COO·CH_{3}