76 ELEMENTS OF BOTANY. 
1038. Experiment 22. Testing for Grape Sugar.— Heat to 
boiling in a test-tube or a small beaker some weak syrup of grape sugar 
or some honey, much diluted with water. Add Fehling’s solution, a few 
drops at a time, until a decided orange color appears. Repeat the test 
with the water in which some slices of onion have been boiled, filtering’ 
the water through a paper filter and heating again to boiling before add 
ing the test solution.! 
Does the onion contain grape sugar ? 
1 The deposit will in this case, even if orange at first, finally become black, prok 
ably owing to the presence of sulphur in the onion. 
