FRUITS AND FRUIT PRODUCTS. 



81 



calcium acetate with constant stirring, and allow to stand from six to twelve 

 hours. Throw the precipitate of calcium tartrate on a filter paper and wash 

 until filtrate and washings make exactly 100 cc; ignite the filter paper and pre- 

 cipitate, and determine the lime by titration. A correction of 0.0'jxi; gram of 

 tartaric acid, which is held in solution In the 100 cc of washings as calcium 

 tartrate, must be added. Evaporate the filtrate down to about 20 cc, and If n 

 precipitate" of calcium citrate is formed collect it on a filter while hot, wash \\ith 

 hot water, ignite, and titrate. From this result calculate the citric acid. 

 Evaporate the filtrate and washings from the calcium citrate to about 20 cc 

 and add three volumes of 9G per cent alcohol by volume, which will throw 

 down the calcium salt of tartaric acid held in solution, the remaining citrate, 

 and the malate and succinate. Filter, ignite the precipitate, titrate, and cal- 

 culate as malic acid after subtracting the tartaric acid present. (The amount 

 of citric and succinic acid present is very small.) 



15. Tartaric Acid. Provisional. 



Determine tartaric acid in 100 cc of the fruit juice as directed for total 

 tartaric acid under " XIII. Wine," page 86, except that 20 cc of alcohol is 

 used in the precipitation instead of 15 cc. 



16. Citric Acid. a Provisional. 



Evaporate 50 cc of the fruit solution on a water bath to a sirupy condition. 

 To the residue add, very slowly at first and with constant stirring, 95 per cent 

 alcohol until no further precipitate is formed, 70 to 80 cc are generally enough. 

 Filter and wash the residue with 95 per cent alcohol. Evaporate the filtrate to 

 eliminate the alcohol, take up the residue with a little water and transfer to a 

 graduated cylinder, making up to 10 cc. To 5 cc of this solution add half 

 a cubic centimeter of glacial acetic acid, and, drop by drop, a saturated solu- 

 tion of lead acetate. The presence of citric acid is shown by the appearance 

 of a precipitate which dissolves when heated and reappears when cooled. In 

 order to separate the citric acid from other acids, heat to boiling, filter, and 

 wash with boiling water, then allow to cool and the precipitate of lead citrate 

 will again form. This lead precipitate may be filtered off, washed with weak 

 alcohol, dtied, weighed, and the citric acid calculated. It is necessary that no 

 tartaric acid be present. If the tartaric acid has been estimated, any error 

 on this account may be avoided by adding enough tenth-normal potash to neu- 

 tralize the tartaric acid before the alcohol is added. 



17. Detection of Preservatives. Provisional. 

 Test as directed on page 179, under " XXVII. Food Preservatives." 



18. Detection of Coloring Matter. Provisional. 

 Follow the directions given under " XXVIII. Coloring Matter," page 190. 



19. Detection of Artificial Sweetening Material. Provisional. 



Follow the directions given under " XXVII. Food Preservatives," pages 182 



anil IS!). 



Moslinger, Zts. Nahr. Genussm., 1899, 2 : 93. 



