264 Researches respecting the radical of Benzoic Acid. 



* 



Urged through a red hot glass tube, it remains undecomposed. 

 In the air, in moist or dry oxygen, it is entirely converted in crystalli- 

 zed benzoic acid. In the sun's ray this change is remakably hasten- 

 ed, beginning in the course of a few moments. The same change 



wi 



formation of benzoate of potassa. If these experiments be made 

 in a glass tube closed with mercury, the rise of this metal proves the 

 absorption of oxygen. 



Beside this conversion of the oil into benzoic acid, no third body 

 is formed. 



The manner of its purification shews that it is not decomposed 

 or changed by anhydrous alkali, but to the hydrated, its behavior is 

 different. Heated with the hydrate of potassa, apart from the air, 

 it forms benzoate of potassa and evolves pure hydrogen gas. 



If the oil be introduced into solution of hydrate of potassa in 

 water, or into alcohol saturated with ammoniacal gas, it is immediately 

 dissolved, and if the air be wholly excluded, a benzoate appears which 

 when potassa is employed, is soon deposited in large shining lamellar 

 crystals. By the addition of water which dissolves the salt, an oily 

 body is separated, which is no longer the oil of bitter almonds. 



In the concentrated nitric and sulphuric acids, the pure bitter al- 

 mond oil is soluble without change. By heating the latter solution, 

 it first becomes a purple-red, and then black with the evolution of 

 sulphurous acid. 



From the action of chlorine and bromine, new compounds arise 

 which will be described in another part of this essay. 



The composition of this pure oil was ascertained in the usual way 

 by ignition with the oxide of copper. To expel the hygroscopic 

 moisture from the oxide of copper, we have employed in our experi- 

 ments a small air pump invented by Gay-Lussac. Since it has not 

 been described by himself, we take the liberty of annexing a sketch 

 of the same ; for it may undoubtedly be viewed as one of the most im- 

 portant improvements with which organic analysis has been enrich- 

 ed, both as regards its convenience in use and the safety it ensures 

 in hydrogen examinations. 



Fig. 1. is the pump alone of half the actual size; it is fur- 

 nished with common bladder valves, and terminates beneath in a strong 

 screw, to fasten it firmly for use. 



Fig. 2. shews the pump as connected with the ignition tube fl> 

 which is united by means of a well fitting cork with a long tube b, 



