Researches respecting the radical of Benzoic Acid. 275 



Lastly under certain circumstances, (of which we yet know but 

 little, but it is probable chiefly when the chlorobenzoyl was not per- 

 fectly free from chlorine), by saturation with ammonia an oily body 

 may be observed, possessing an aromatic odor resembling bitter al- 

 monds, and by which the contained benzamide has the property, be- 

 fore it is dissolved, to melt to an oil by warming with water, and again 

 to separate from the solution in the form of drops of oil, which con- 

 geal in a short time. 



Pure benzamide shews a remarkable phenomenon in its crystalli- 

 zation. It deposites from a boiling hot solution by rapid cooling, 

 pearly, leafy crystals very similar to chlorate of potassa. By long 

 cooling and at a certain concentration, the whole liquid congeals to 

 a white mass consisting of very fine, silky crystals resembling cafFein. 

 After one or more days and often after a few hours, large cavities 

 may be observed in this mass, in the centre of which may be observ- 

 ed one single or several large well formed crystals, into which the 

 silky fibre has been converted j and gradually this change of form 

 spreads throughout the mass. 



The form of the crystals of benzamide is a right-rhombic prism, 

 which by the enlarging of two opposite planes becomes tabular. They 

 have a highly nacreous lustre, are transparent and exhibit upon water 

 a fattiness, easily swimming on its surface. 



At 115° C. it melts to a water-like liquid, which congeals by cool- 

 ing to a large-leaved crystalline mass, wherein are frequently found 

 cavities with well formed crystals. At a stronger heat it boils and 

 distills over unchanged. Its vapor is similar in odor to bitter almond 

 oil. It is easily inflammable and burns with a sooty flame. 



In cold water, the crystallized benzamide is so little soluble that the 

 solution scarcely possesses taste. In alcohol on the contrary it is 

 readily soluble. In boiling ether it is also dissolved, and from this 

 solution in particular can be obtained in well defined crystals. 



Covered with caustic potassa at common temperature, the benza- 

 mide evolves no ammonia. Nor does its solution mingled with a salt 

 of iron at common temperature give a precipitate, as indeed it in gen- 

 eral gives no reaction with a metallic salt. By boiling the benzamide 

 with a concentrated solution of caustic potassa, ammonia is evolved 

 in abundance and a benzoate of potassa remains. By heating to 

 boiling the solution of benzamide mixed with a salt of iron, it becomes 

 cloudy and throws down a benzoate of iron. 



Vol. XXVL— No. 2. 36 



