$70 VEGETO-ALKAI.IES. 



proving that the acroleine comes from the glycerin. It is, in- 

 deed, produced in large quantity by the distillation of pure 

 glycerin. Hence the occurrence of acroleine among the pro- 

 ducts of the distillation of a fat or oil is a sure and delicate test 

 of the presence of glycerin in the oil. 



Acroleine is unknown in a state of purity. It absorbs oxygen 

 with great rapidity from the air and becomes acid. Its solution 

 is decomposed even in close vessels, and yields a tasteless, in- 

 odorous, and very indifferent white solid, not resembling fat, 

 and insoluble in all menstrua yet tried. No compound of acro- 

 leine has been formed from which it can again be obtained. 

 (Liebig). 



CHAPTER IX. 



VEGETO-ALKALIES. 



IN the class of organic bases are included a number of bodies 

 containing nitrogen, which have the properties of the basic or 

 metallic oxides, and form salts with acids. These salts perfectly 

 resemble salts of metallic oxides ; the acids which they contain 

 continue to be affected by the usual reagents, sulphate of mor- 

 phine and sulphate of soda being equally precipitated by chloride 

 of barium, and the organic bases themselves are liberated by 

 stronger bases. Oxide of ethyl and oxide of methyl are like- 

 wise bases; but in salts of these, acids have their properties dis- 

 guised, and can no longer be transferred to other bases such as 

 the metallic oxides, by double decomposition ; the compounds 

 of the last mentioned bases with acids diverge therefore widely 

 in their properties from common salts. The present class of 

 organic basis are principally derived from plants, and are known 

 as the vegeto-alkalies. The solutions in water of such of them 

 as are soluble in that liquid, and their solutions in alcohol 

 restore the blue colour of reddened litmus and render yellow 

 turmeric paper brown ; they are therefore unequivocally alka- 

 line. The following organic bases appear to be allied to the 

 class of vegeto-alkalies, ammeline, melamine, aniline or crystalline, 

 urea, with certain bases still problematical which Unverdorben 



