8 CHANGES DURING THE SPOILAGE OF TOMATOES. 



Significant determinations made on commercial products Continued. 



CITRIC ACID DETERMINATIONS. 



The method which is proposed for the determination of citric acid 

 in ketchups is as follows : 



Weigh 25 grams into a 250 cc beaker, make up to approximately 200 cc with 

 95 per cent alcohol, allow to stand with frequent stirring for four hours, filter through 

 a folded filter and wash with 50 cc of 80 per cent alcohol. To the filtrate add suf- 

 ficient water to dilute the alcohol to 50 or 60 per cent and then add 10 cc of 20 per 

 cent barium acetate solution, stir well with a glass rod, and allow to stand over night. 

 In the morning filter on a Gooch crucible, washing with 50 per cent alcohol, dry for 

 from 3 to 4 hours in an oven at 100 C. and weigh. Weight of precipitate times 0.51 

 equals anhydrous citric acid. 



This method approximates very closely the amount of citric acid 

 present in such a product, as was proved by sending out to a number 

 of chemists solutions containing about 20 per cent of sugar and v 

 known amounts of citric and lactic acids. The amounts of citric 

 acid found in these solutions were very close to the actual amount 

 present. 



Unfortunately there is at present no convenient method for the 

 determination of citric acid in solutions of the type of a ketchup which 

 gives absolutely accurate results. The method as given has been 

 very thoroughly tested and has been found to give results of suf- 

 ficient accuracy for the purpose at hand. It may not be amiss to 

 give a few details as to attempts which were made to find a better 

 method for the determination of citric acid. Beau 1 gives a method 

 for the determination of citric acid, in milk, using the Deniges 2 



1 Rev. ge"n. du lait, 1904, p. 386; Chem. Centrbl., 1904, 75 (2): 856. 



2 Ann. chim. phys., 1899, (7) 18: 413. 



