20 
Ingvar Jorgensen and Walter Stiles. 
Experiment 12. Microscopic examination of ethyl chloropliyllide. 
Prepare sections of fresh Heracleum leaves and mount them 
n a drop of 90% alcohol. Leave the slide under a bell jar contain¬ 
ing a dish of alcohol. The section slowly dries in the course of 
half a day or a day. It is then examined under the microscope 
when there will be observed the characteristic triangular and 
hexagonal crystals of ethyl chlorophyllide (crystalline chlorophyll). 
Experiment 13. Production of methyl chlorophyllide in the leaf. 
Sections may be used as in the preceding experiment, or a 
piece of a leaf may be employed. In the latter case a test-tube 
with 4 c.c. 75% methyl alcohol is taken and 1 gram of fresh leaf is 
added to it. The leaf first becomes a darker green and then during 
the course of a few hours becomes yellowish. On holding the leaf 
to the light there can be observed with the naked eye a number of 
black points. If sections of the leaf be cut and examined under the 
microscope, these spots appear as aggregates composed of rhom- 
bohedral crystals, occurring only in certain cells. 
Experiment. 14. Extraction of ethyl chlorophyllide. 
Two grams of dry Heracleum leaf powder is left for a day in a 
test-tube containing 6 c.c. 90% alcohol. The extract is then 
filtered through a small Buchner funnel and the powder on the 
filter washed with a little acetone. The filtrate is washed with the 
same quantity of ether, and then with water. The ether solution is 
transferred to a separating funnel and washed with water, and then 
concentrated on a water bath to ^ or 1 c.c., and 3 c.c. petrol ether 
is added. On standing, the ethyl chlorophyllide is precipitated in 
the form of crystalline aggregates. It is freed from yellow pigments 
by shaking with a little ether, and can be further purified by 
redissolving in ether and precipitating again with petrol ether. 
Experiment 15. Spectroscopic examination. Required: small 
spectroscope and glass vessel with parallel sides of about 1 cm. in 
width; source of light (incandescent burner or Nernst lamp or 
sunlight). 
The following absorption spectra may be examined :— 
a. Chlorophyll spectrum from acetone extract obtained in Experiment 7. 
The extract is diluted with about five times its volume of 85% 
acetone. The spectrum shows a main absorption in the red at the 
Fraunhofer line C. Then follow, towards the violet, three absorp¬ 
tion bands decreasing in intensity, and the. end absorption in the 
