LIVING PARTS OF THE STEM Ei 
orange color and throwing down an orange or reddish 
deposit, when they are added to a brilliant blue alkaline 
solution of copper, known as Fehling’s solution! The 
color or deposit will not appear until the solution has 
been heated to boiling. 
EXPERIMENT XXIV 
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 
adding the test solution.? 
127. Proteids in the Onion.— Since the onion grows 
so rapidly on being planted in the spring, there must be 
a large supply of food in the bulb; there may be other 
substances present besides sugar. 
EXPERIMENT XXV 
Testing an Onion for Other Stored Food. — Test a rather thick 
slice of onion by heating it in a porcelain evaporating dish with a 
little strong nitric acid until the latter begins to boil and the onion 
becomes somewhat softened.? Rinse off the slice of onion in a stream 
of water, then pour on it a few drops of ammonium hydrate and 
observe any change of color. What is proved? See Sect. 29. 
128. Tabular Review of Experiments. 
[Continue the table from Sect. 74:] 
1 For the preparation of the solution see Handbook. 
2 The deposit will in this case, even if orange at first, finally become black, 
probably owing to the presence of sulphur in the onion. 
3 Do not allow the acid to touch the clothing, the hands, or any metallic 
object. 
