Researches respecting the radical of Benzoic Acid. 279 



The analysis of benzoic ether, by Dumas, varies materially from 

 ours in the hydrogen content. Let this serve to shew how difficult 

 it is to become free from preconceived opinions in researches of a 

 similar kind. 



Benzoin. — The body which we would denote by this name on ac- 

 count of its relation to the suhstances treated of in this essay, has 

 indeed been already examined by Stange, but scarcely farther than 

 in its external properties- It is the same which is introduced into 

 chemical works as bitter almond oil, camphor or camphoroid. 



Benzoin arises under certain circumstances from the oil of bitter 

 almonds. We obtained it, for example, accidentally, as others have 

 done before us, by the rectification of the oil with caustic potassa, 

 where it remains swimming upon the potassa. We produced it how- 

 ever in greater quantity by suffering the bitter almond oil, to stand 

 several weeks with a concentrated solution of caustic potassa. Robi- 

 quet and Charlard, have also noticed the same change in contact with 

 alkali when free from the access of air. We can confirm this ob- 

 servation. In our experiment the oil was almost wholly converted 

 into solid benzoin, though only after several weeks. Lastly, w T e pro- 

 duced it by saturating water with bitter almond oil and mingling the 

 solution with some caustic potassa. In a few days the benzoin be- 

 gins to deposite in needle-form crystals. 



In all these cases the benzoin possesses at first more or less a yel- 

 low color, but is rendered perfectly pure and colorless by solution in 

 hot alcohol, treatment with blood charcoal and frequent crystallization. 



Benzoin forms clear, highly lustrous, prismatic crystals. It pos- 

 sesses neither taste nor smell. At 120° it melts to a colorless li- 

 quid, which again congeals to a large striated crystalline mass. At 

 a stronger heat it boils and distils over unchanged. It is inflam- 

 mable, and burns with a clear, sooty flame. It is insoluble in cold 

 water, but if the latter be boiling, a small portion is dissolved, which 

 again separates by cooling in capillary crystals. It is taken up by 

 hot alcohol in much larger quantity than by cold. 



It is decomposed neither by concentrated nitric acid, nor by a 

 boiling solution of caustic potassa. With concentrated sulphuric 

 acid on the contrary, it at first gives a violet blue solution soon be- 

 coming brown and by warming it takes a deep green color, with the 

 evolution of sulphuric acid and blackening of the whole mass. 



This body as we perceive, offers but little interest in its proper- 

 ties ; but it is the more remarkable in its relation to hydrobenzdyl, 



