g()0 ANALYSIS OF ONIONS. 



Potash treated The action of oxigen gas and bidrogen gas on potash lias 

 with oxigen & ,-, , ,. ' ... . , „ , . , 



hidrogen gas 1,feewise presented us with some phenomena, ot which we 

 shall give an account. ' 



VII. 



On the Chemical Analysis of the Onion: by Messrs. Four- 

 croy and Vauquelin *. 



Liliaceous /1.MONG the plants that compose the very natural fa- 



plants similar 

 in structure. 



milj of liliaceee, and seem to have the same interior organ- 

 yet widYlydif- ization, there are some, which, as the onion, differ essen- 



ferent in pro- t j a j] v m their taste, smell, and almost all their properties. 

 peities. J . i • 



The authors of the paper, of which we shall here give an 



abridgment, had in view to seek thecausesof thisdifference. 

 Beside the solution of this problem, their investigation in- 

 cludes several chemical facts of great importance to the pro- 

 gress of vegetable analysis. 

 Properties of The onion, allium cepa, grated to a pulp, and subjected 

 thejuiceof the to ^ ]Q ac{ " on Q f a p Ves s, gives out a white viscid juice, 

 somewhat opake, of a strong smell, colourless the instant 

 it is filtered, but acquiring a rosy hue from the contact of 

 the air, on account of the oil it contains. It is perceptibly 

 acid. It is precipitable by the acetate of lead, lime, oxalic 

 acid, nitrate of silver, and potash. Distilled it yields a 

 milky water, slightly acid, with a few drops of oil floating 

 on the surface. 

 The water dis- The water distilled from onion juice has a strong smell, 

 ^ l c f ^ s e and forms a light yellow precipitate with acetate of lead, 

 sulphur. Two experiments were sufficient to prove the existence of 



sulphur in this liquor. 1. Oximuriatic acid makes it clear, 

 deprives it of its smell, and gives it the property of preci- 

 pitating nitrate of barytes. 2. This liquor, distilled in a 

 copper alembic, forms on the surface of the head a b'ack 

 iridescent pellicle, which is sulphuret of copper. The 

 sulphur is held in solution in the onion juice by an essen- 



* Annales de Chimie, vol. LXV, p. 161. Abridged by Mr. Laugier 

 from the original paper read Co the National Instil ute. 



tial 



