46 



PRACTICE 22. 



PREPARATION OF A NEUTRAL AMMONIUM CITRATE SOLUTION.* 



To 370 grams of commercial citric acid add commercial ammonia, spe- 

 cific gravity .96, until nearly neutral; reduce the specific gravity to nearly 

 1.09 and make exactly neutral, testing as follows: Prepare a solution of 

 fused calcium chlorid, 200 grams to the liter, and add one-fourth volume 

 of strong alcohol. Make the mixture exactly neutral, using a small amount 

 of freshly prepared corallin solution as a preliminary indicator, and test 

 finally by withdrawing a portion, diluting with an equal volume of water, 

 and testing with cochineal solution; 50 cc. of this solution will precipi- 

 tate the citric acid from 10 cc. of the citrate solution. To 10 cc. of the 

 nearly neutral citrate solution add 50 cc. of the alcoholic calcium chlorid 

 solution, stir well, filter at once through a folded filter, dilute with an 

 equal volume of water, and test the reaction with a neutral solution of 

 cochineal. If acid or alkaline, add ammonia or citric acid, as the case may 

 be, mix, and test again, as before. Repeat this process until a neutral re- 

 action is obtained. Add sufficient water to make the specific gravity 1.09 

 at 20. 



*To be done by the instructor. 



