KETONES 91 



lodoform Reaction (Lieberi}. 



Acetone gives iodoform in the cold ; 3-5 drops of sodium hydrox- 

 ide are added to about 2 c.c. of the solution and then, drop by drop 

 iodine solution until the liquid is faintly yellow. lodoform separates 

 at once. 



If ammonia be used in place of sodium hydroxide and iodine 

 solution be added drop by drop, a small black precipitate of nitrogen 

 iodide is formed. On standing, or on warming, this disappears and 

 iodoform is produced; this reaction may serve to distinguish acetone 

 and alcohol. 



Sodium Nitroprusside Test (Legal}. 



On adding about 5 drops of freshly prepared sodium nitroprusside 

 solution to about 5 c.c. of the dilute acetone and about I c.c. of sodium 

 hydroxide, a ruby-red colour is produced. This fades to yellow oa- 

 standing. 



If the reaction be repeated and the solution acidified at once with*, 

 acetic acid, a purple-red colour is produced. 



Rothera suggests that the reaction be carried out by adding 3 drops 

 of 5 per cent, sodium nitroprusside and 1-2 c.c. of ammonia to the 

 dilute acetone and a small quantity of solid ammonium sulphate. A 

 permanganate colour slowly develops, reaches a maximum in about 

 30 minutes and then fades away. 



Creatinine does not react under these conditions ; a brownish-red^ 

 colour is given by aldehydes. 



Salicylic Aldehyde Test. 



i gm. of solid potassium hydroxide is added to 10 c.c. of the acetone- 

 solution, and before it dissolves 10 drops of salicylic aldehyde are added. 

 On warming to 70 a purple-red contact ring appears. If the potash has dis- 

 solved before adding the salicylic aldehyde .the liquid becomes yellow, red, 

 and finally purple-red. 



JVta?. The iodoform, nitroprusside and salicylic aldehyde reactions are 

 carried out preferably incolourless solutions. The acetone should be separated 

 by distillation and the distillate tested. 



