478 



anhydride of phthalic acid, C 6 H 4 .(COOH) 2 ) and 0.1 gram of phenol 

 C 6 H 5 .OH in a test-tube, add 2 drops of concentrated sulphuric 

 acid, and heat carefully for a minute over a small flame. The 

 mixture, which should be well shaken during the heating, will 

 turn dark-red in color. Allow to cool, add a few c.c. of water, 

 and then add drop by drop a dilute solution of sodium hydroxide 

 until a pink color persists on shaking. 



Take a portion of this solution, and test the action of phenol- 

 phthalein as an indicator by adding first dilute hydrochloric acid, 

 then dilute sodium hydroxide (see p. 168). 



(b) Fluorescein. To 0.1 gram of phthalic anhydride and 0.1 

 gram of resorcinol CeH^OH^ add 3 drops of concentrated sul- 

 phuric acid, and heat carefully for a minute. Allow to cool, add 

 a few c.c. of water, then add sodium hydroxide until alkaline 

 (use litmus paper as a test). 



Shake up a few drops of this solution with a test-tube of water. 

 The dye imparts to the solution a brilliant green fluorescence, 

 hence its name. 



Perfumes. Many natural perfumes and fruit flavors can 

 also be produced synthetically. The basis of most of these con- 

 sists of esters (p. 349). The fragrance of ripe apples is due to 

 minute amounts of the amyl esters of formic, acetic and caproic 

 acids. In bananas the characteristic ester is amyl acetate; in 

 grapes it is methyl anthranilate. Almond flavor is due to benz- 

 aldehyde, C 6 H 5 .CHO; the smell of geraniums to diphenyl ether, 

 (CeHs^O. The chief ingredient of otto of roses is geraniol; of 

 the vanilla bean, vanillin; of the perfume sold as " new mown 

 hay," coumarin; all complex hydrocarbon derivatives which 

 are now commercial products. Some of the synthetic flavors 

 and perfumes on the market are identical with the substances 

 that give odor to fruits and flowers; others are merely more or 

 less adequate imitations. Thus, natural oil of wintergreen is 

 essentially the same as synthetic methyl salicylate. On the other 



