112 



into crystals, the melting-point of which is also 10C. The alde- 

 hyde here described under the name Elaldehyde is identical with 

 that of Weidenbush*. Its mode of production from common alde- 

 hyde is the same ; its boiling-point likewise agrees with that of 

 the aldehyde of Weidenbush. 



The elaldehyde of Fehlingf the authors believe to be identical 

 with that they have obtained, and also that obtained by Weidenbush. 

 That which goes far to prove the identity of the two latter is their 

 vapour-densities. That of Weidenbush' s is given as 4 '58, whilst that 

 of Fehling's is 4'52 ; both are converted into common aldehyde by 

 heating gently with dilute sulphuric acid, and both crystallize at low 

 temperatures. The only material discrepancy between them is the 

 boiling-point of 94 C. given by Fehling for elaldehyde, whilst Wei- 

 denbush gives the boiling-point of his aldehyde as 125C. 



III. Oil of Bitter Almonds. 

 1 . Oil of Bitter Almonds and Hydrochloric Acid. 

 This acid does not combine with oil of bitter almonds. Ex- 

 periments made in sealed tubes, heated first to 100C., and after- 

 wards to 200, gave no signs of a combination having been effected. 



2. Oil of Bitter Almonds and Hydriodic Acid. 

 Much better results can be obtained when hydriodic acid is 

 allowed to act on oil of bitter almonds. The gas is absorbed, pro- 

 ducing an increase of volume and of temperature, and at the same 

 time a little water. At the end of the operation two layers appear, 

 of a dark-brown colour. The upper one, which is about a sixth 

 part of the quantity of the under one, consists of concentrated hy- 

 driodic acid, whilst the under one, a heavy oil, is a compound of 

 iodine and oil of bitter almonds. To obtain the substance in a pure 

 state, it was first washed well with water, to remove excess of the 

 acid ; next treated with moderately strong solution of sulphite of 

 soda, to remove any excess of oil ; lastly, on washing with water, the 

 salt was removed from it. It can be dried rapidly over sulphuric 

 acid at a temperature not higher than 20 C. A higher temperature 

 produces gradual decomposition. In the preparation of this sub- 



* Liebig's Annalen, vol. Ixvi. p. 155. 

 | Liebig's Annalen, vol. xxvii. p. 320. 



