Messrs. Perkin aw«? Duppa on lodacetic Acid. 55 



with water to separate any remaining bromide of potassium, con- 

 stitutes the iodacetate of ethyle. Its formation will be easily 

 understood as under : — 



C4 H^ C4(H2 £00"+ KI = C4 H^ C4(H2 1)0" + K Br. 

 Bromacetate of ethyle. Iodacetate of ethyle. 



To obtain iodacetic acid from this compound, it is first con- 

 verted into the barium salt, which is afterwards decomposed by 

 sulphuric acid in the following manner. 



The new ether is agitated with hydrate of barium and water 

 in the cold, which soon decomposes it ; the excess of hydrate 

 of barium is separated by means of a filter, and carbonic acid 

 passed through the filtrate throws down any that may be in 

 solution ; it is again filtered, and the resulting liquor carefully 

 evaporated and allowed to crystallize. The iodacetate of barium 

 thus obtained is then dissolved in water, and decomposed by very 

 cautiously adding dilute sulphuric acid until all the barium is 

 precipitated as sulphate ; by this means an acid liquid is obtained, 

 which is then concentrated in vacuo over sulphuric acid until it 

 crystallizes. These crystals consist of crude iodacetic acid, and 

 are rendered pure by being recrystallized two or three times. 



Thus obtained, iodacetic acid is a colourless substance, cry- 

 stallizing in thin, tough, phable, rhombohedral plates, which, 

 when pressed together, look like mother-of-pearl. It is not de- 

 liquescent. It has a very acid taste. It fuses at 82° C, and 

 solidities at 81-5; even at this low temperature it undergoes 

 sHght decomposition, becoming pink from free iodine: at a 

 higher temperature it is quite decomposed, iodine being evolved 

 in considerable quantities ; a small quantity of the acid appears 

 at the same time to be volatilized, and has a smell similar to 

 bromacetic acid. 



Hydrate of silver added to the acid, or any of its salts, imme- 

 diately seizes on the iodine and forms glycolic acid. 



The following combustions and iodine determinations were 

 made, and, as it will be seen, agree very well with theory : — 



I. -7902 of acid gave -3716 of carbonic acid*. 



II. -9890 of acid gave -4659 of CO^ and -1610 of water. 



III. -5420 of acid gave -6787 of iodide of silver, 



Per-centages : — 



I. II. III. 



Carbon . . . 12-83 12-83 



Hydrogen 158 



Iodine 67-89 



* The hychogen was lost. 



