22 
J. H. Priestley 
and pure, viz. phellonic acid m.p. 95-96° C., percentage composition 
suggesting the formula C 22 H 43 0 3 , and phloionic acid, crystallising in 
fine white needles, m.p. 120-12 i° C., percentage composition varying 
with prolonged drying from C n H 21 0 4 to C 22 H 40 O 7 . 
Another amorphous substance, semi-liquid, which Gilson terms 
suberinic acid, was obtained in relatively large quantities and, if it 
can be regarded as pure, its composition would agree with the 
formula Ci 7 H 30 O 3 . 
Of these suberogenic acids, phellonic was most completely studied, 
being obtained relatively easily in considerable quantities in the 
pure state, but all three acids possess one very important property. 
Both the acid and some of the salts, on heating for some time in 
sealed tubes, tend to go over into other forms, possibly anhydride 
or condensation products, which differ materially from the original 
suberogenic acid. The latter is soluble in the usual fatty solvents, 
at any rate on warming, the anhydrides are quite insoluble; the 
acid or some of its salts may be soluble or at least have a tendency 
to swell in water, whilst the new product is quite unaffected by the 
presence of water. 
The significance of these facts for the formation of suberin is 
obvious. An experiment which has been carried out successfully in 
the laboratory gives an excellent demonstration of the possible 
significance of the suberogenic acids in the formation of impermeable 
membrances. 
An ordinary Soxhlet thimble, as used in fat extractions, consists 
of a fat free cellulose preparation, readily permeable to water. One 
of these thimbles was taken and impregnated with a concentrated 
solution of potassium phellonate in hot chloroform. The thimble was 
then dried until all the chloroform had evaporated and then sealed 
up in a wide glass tube after partial exhaustion by a Geryk air-pump. 
This sealed tube was then heated to about 180° C. on successive 
days for a total of about twenty-four hours in all. The phellonate in 
the thimble partly volatilised on to the walls of the tube but enough 
was left to impregnate the thimble thoroughly with the resulting 
anhydride or condensation product. 
After heating, the potassium phellonate could no longer be re¬ 
moved from the thimble by the action of boiling fatty solvents and 
was obviously altered in its nature. This new substance rendered 
the Soxhlet thimble completely impermeable to water, the outer 
surface remaining quite dry to the touch when the thimble was filled 
to the brim with water and left for several hours. 
