378 CONSIDERATION OF CARBON COMPOUNDS. 



gently and set aside for a few minutes. On reheating, the odor of 

 methyl salicylate is developed. 



Salicin, C 13 H 18 7 . This glucoside is found in several species of Salix (willow), 

 and is mentioned here because it splits into glucose and salicylic alcohol, 

 C 6 H 4 .OH.CH 2 OH, when boiled with dilute acids : 



C 13 H 18 7 + H 2 = C 6 H 12 + C 7 H 8 2 . 



Salicylic alcohol is converted by chromic acid into salicylic aldehyde, C 6 H 4 

 OH.COH, which by further oxidation is converted into salicylic acid. 



Salicin forms white, silky, shining needles, which are soluble in less than an 

 equal weight of water, have a neutral reaction and a very bitter taste. 



Salicin sprinkled upon concentrated sulphuric acid produces a red color. 

 Boiled with very dilute hydrochloric acid for a few minutes, and this solution 

 nearly neutralized with sodium carbonate, a violet color is produced on the 

 addition of a drop of ferric chloride solution. 



Methyl salicylate, CH 3 .C 7 H 5 3 . Oil of wintergreen is chiefly methyl sali- 

 cylate, a nearly colorless liquid with a characteristic, strongly aromatic odor. 

 It is made by the method so extensively used in the manufacture of compound 

 ethers, viz., by heating of salicylic acid with methyl alcohol in the presence of 

 sulphuric acid. (See above reaction 3 of salicylic acid.) 



Phenyl salicylate, Salol, C 6 H 5 .C 7 H 5 O 3 . This compound ether is 

 a white, crystalline, tasteless powder, which is nearly insoluble in 

 water, readily soluble in alcohol, ether, and benzol, and fuses at 42 

 C. (107.4 F.). It is used as an antiseptic and antipyretic. 



Salol heated with potassium hydroxide solution causes its decom- 

 position into phenol, which can be recognized by its odor, and potas- 

 sium salicylate, from which crystalline salicylic acid will separate 

 upon supersaturating the liquid with hydrochloric acid. An excess 

 of bromine-water produces a white precipitate in an alcoholic solution 

 of salol. 



Salol is made by the action of suitable dehydrating agents upon a 

 mixture of phenol and salicylic acid : 



C 6 H 5 OH + HC 7 H 5 3 = C 6 H 5 .C 7 H 5 3 + H 2 O. 



Phtalic acid, C 6 H 4 .(C0 2 H) 2 , is a dibasic acid, which, when heated, loses 

 water, and is converted into phtalic anhydride : 



C 6 H 4 .(C0 2 H) 2 : : H 2 + C 6 H 4 C 2 3 . 



The latter compound, when treated with phenol in the presence of sulphuric 

 acid, forms phenol-phtalein: 



2C 6 H 6 + C 8 H 4 3 = H 2 + C 20 H 14 4 . 

 Phenol. Phtalic anhydride. Phenol-phtalein . 



A solution of phenol-phtalein shows a purplish-red color in the presence of 

 alkalies ; this color is destroyed by acids. This property is made use of in 

 alkalimetry, where phenol-phtalein serves as an indicator. 



