Pyraconitic and Citraconic Acids. 287 



arrives at the same formula, C" H'-0+, and states that this 

 therefore is a combination of the oxide of ethyl, with an acid 

 of the same constitution as .iconitic acid. 



The free aconitic acid is easily soluble in water, alcohol 

 and aether ; decomposes on being heated above its melting 

 point, disengaging pyraconitic acid, empyreumatic oil, and 

 leaving behind a black pitchy mass, which subsequently car- 

 bonizes entirely. 



Itaconic acid (pyraconitic acid) is best obtained by heating 

 the aconitic acid in a retort till the evolution of yellow va- 

 pours occurs. It is, further, this acid which forms the oily bands 

 when the second period in the distillation has commenced : 

 carbonic acid and water appear simultaneously with it. It 

 condenses to an oily mass which sometimes passes into a cry- 

 stalline solid. As soon as yellow vapours and empyreumatic oil 

 begin to appear the distillation is to be stopped. On slowly 

 cooling acicular crystals are formed in it, and the remaining 

 mass no longer solidifies. On being rapidly cooled the oily 

 acid solidifies entirely, and may be obtained pure by solution 

 in six times its volume of water, and slow evaporation ; colour- 

 less by recrystallization from alcohol or aether. From the 

 aqueous solution it crystallizes in the form given by Baup for the 

 citricic acid. The crystals give off no water at 100° cent., and 

 consist of 46'62 C, 4*56 H, 48 82 O, agreeing perfectly with 

 Baup's analysis of the acide citricique. On being heated to its 

 boiling point, it passes into the isomeric volatile citraconic 

 acid. The acid potash salt is easily soluble, crystallizes in 

 small shining laminae, which lose one atom of water at 100°; the 

 dried salt contains 28*06 per cent, potash. The neutral baryta 

 salt crystallizes in long slender stellate groups, which lose no 

 water at 100°, it contains 54-92 per cent, barytes. The acid salt 

 forms crystalline crusts. Neither salt of lime is distinctly cry- 

 stalline. The neutral strontia salt resembles that of barytes, and 

 contains 45'69 per cent, strontia. The silver salt forms a white 



powder nearly insoluble in water ; formula = C^ H^ O^ Ag. 

 The atomic weight determined from the silver salt = 707*12, 

 and its symbol It. Itaconic aether had already been de- 

 scribed by Malagutti as pyrocitric aether ; it is colourless, of 

 aromatic odour and bitter taste; specific gravity = 1*050 at 

 15°, boiling point = 227°; it is partially decomposed at a 

 liigher temperature : it consists of C' H'^ 0' = Ae O, It. 



The same a^dier has likewise been prepared by Marchand ; 

 by continuing the distillation of his mixture for a longer time, 

 he found for it the same constitution. 



The citraconic acid is identical with Baup's acide citribique 



