BY JAMES M. PETRIE. 531 



distilled with a little sulphuric acid, the distillate obtained is 

 strongly acid; it turns ferric chloride solution red, and silver 

 nitrate paper held in the steam is instantly blackened. 



A volatile acid therefore exists in the fresh leaves partly as 

 free acid, and the greater part combined as a non-volatile com- 

 pound. The free acid quickly evaporates when the leaves dry, 

 and only the neutral compound remains. The presence of formic 

 acid is indicated. 



Tested on the growing tree, the juice of leaves and stalks is 

 strongly acid, and when a piece of blue litmus paper is gently 

 pressed on the hairs numerous red points are observed. 



Separation and identification of the organic acids. — 100 grams 

 of the air-dried leaves were distilled with water and 2 % of phos- 

 phoric acid, until the distillate ceased to give an acid reaction. 

 The whole of the acid was obtained only after 24 litres had 

 collected. In the first part of the distillate a thin layer of a 

 fragrant yellow oil was observed on the surface, and a small 

 amount of a white fatty solid formed in the condenser. This 

 very bulky distillate was filtered to remove the oil and fatty 

 substance, and then neutralised with standard alkali; 200 cc.y^- 

 potassium hydroxide were required. The solution was evaporated 

 to dryness and weighed. The equivalent of K added being 

 known, the approximate amount of the total organic acid could 

 be calculated : — 



Organic acid = l - 56 °/ o on the air-dried leaves. 

 0-365 % on the fresh leaves. 



The potassium salts were distilled twice with phosphoric acid, 

 and the final distillate of free acid was used for the separation of 

 the constituents. 



The Ba salt was first prepared, then converted into sulphate, 

 and the equivalent calculated. This gave an organic acid with 

 molecular weight 62, and showed that acids other than formic 

 were present. During the decomposition of the Ba salt strong 

 vapours of acetic acid were recognised, and a drop of alcohol gave 

 the characteristic ester. 



