PRACTICE XXVIII 



PREPARATION OF A NEUTRAL AMMONIUM CITRATE SOLUTION 



To 370 g. of commercial citric acid add commercial ammonia (sp. 

 gr. .96) until nearly neutral ; reduce the specific gravity to nearly 

 1.09 and make exactly neutral, testing as follows : Prepare a solu- 

 tion of fused calcium chlorid, 200 g. to the liter, and add one fourth its 

 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 precipitate 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 reac- 

 tion is obtained. Add sufficient water to make the specific gravity 

 1.09 at 20. 



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