96 METHODS OF ANALYSIS. 



25 to 50 cc of tenth-normal alkali, and either boil for one hour with a reflux 

 condenser, cool and titrate with tenth-normal acid, or allow the solution to 

 stand overnight in a stoppered flask with the excess of alkali, heat with a tube 

 condenser for one-half hour at a temperature below the boiling point, cool, and 

 titrate. The number of cubic centimeters of tenth-normal alkali used in the 

 saponification of the esters is calculated as ethyl acetate. One cubic centimeter 

 of tenth-normal alkali equals 0.0088 gram of ethyl acetate. 



8. Aldehydes. Provisional, 

 (a) PREPARATION OF REAGENTS. 



(1) Alcohol free from aldehydes. Prepare by first redistilling the ordinary 

 95 per cent alcohol over caustic soda or potash, then add from 2 to 3 grams JUT 

 liter of m-phenyleuediamin hydrochlorid, digest at ordinary temperature for 

 several days (or reflux on the steam bath for several hours) and then distil 

 slowly, rejecting the first 100 cc and the last 200 cc. 



(2) Sulphite- fuchsin solution. Dissolve 0.50 gram of pure fuchsin in 500 cc of 

 water, then add 5 grams of SO 2 dissolved in water, make up to a liter, and allow 

 to stand until colorless. Prepare this solution in small quantities, as it retains 

 its strength for only a very few days. 



(8) Standard acetic aldehyde solution. Prepare according to the directions 

 of Vaseyo as follows: Grind aldehyde ammonia in a mortar with ether and 

 decant the ether. Repeat this operation several times, then dry the purified 

 salt in a current of air and finally in a vacuum over sulphuric acid. Dissolve 

 1.386 grams of this purified ammonium aldehyde in 50 cc of 95 per cent alcohol, 

 to this add 22.7 cc of normal alcoholic sulphuric acid, then make up to 100 cc and 

 add 0.8 cc to compensate for the volume of the ammonium sulphate precipitate. 

 Allow this to stand over night and filter. This solution contains 1 gram of 

 acetic aldehyde in 100 cc and will retain its strength. 



The standard found most convenient for use is 2 cc of this strong aldehyde 

 solution diluted to 100 cc with 50 per cent alcohol by volume. One cubic centi- 

 meter of this solution is equal to 0.0002 gram of acetic aldehyde. This solution 

 should be made up fresh every day or so, as it loses its strength. 



(b) DETERMINATION. 



Determine the aldehyde in the distillate prepared for esters. Dilute from r> to 

 10 cc of the distillate to 50 cc with aldehyde-free alcohol (50 per cent by volume). 

 add 25 cc of the fuchsin solution, and allow to stand for fifteen minutes at 15 r. 

 The solutions and the reagents should be at 15 C. before they are mixed. Pre- 

 pare standards of known strength in the same way. 



9. Furfural. Provisional, 

 (a) PREPARATION OP REAGENTS. 



(1) Standard furfural solution. Prepare by weighing 1 gram of redistilled 

 furfurnl and dissolving it in 100 cc of 95 per cent alcohol. This strong solution 

 will keep. Standards are made by taking 1 cc of this solution and diluting to 

 100 cc with 50 per cent by volume alcohol. One cc of this solution contains 

 0.0001 gram of furfural. 



Analysis of Potable Spirits, p. 30. 



