14 FRUITS AND FKUIT PRODUCTS. 



EXAMINATION OF ASH. 

 ALKALINITY. 



Into the platinum dish containing the ash run an excess of fifth- 

 normal nitric acid and add a few drops of methyl orange. Carefully 

 rub up the ash with a rubber-tipped stirring rod and titrate the excess 

 of acid with decinormal potassium hydroxid. Calculate the alkalinity 

 as per cent of potassium carbonate in the original substance. One 

 cubic centimeter of decinormal acid equals 0.00691 gram of potassium 

 carbonate. 



SULPHATES AND CHLORIDS. 



Wash the ash into a 50 cc flask and make up to the mark with water. 

 In 25 cc of this solution determine the sulphates by precipitation with 

 barium chlorid. The weight of barium sulphate times 0.7478 gives 

 the weight of sulphates calculated as potassium sulphate. 



In the other portion of the solution determine the chlorids b}^ the 

 Volhard a method for chlorin. The nitric acid added before making 

 the titration will, if it contain enough nitrous oxid, completely destroy 

 the red color of the methyl orange and leave a clear solution for the 

 titration. Calculate the chlorin as sodium chlorid. 



The determination of sulphates and chlorids in the amount of mate- 

 rial above named is possible only with fruit products containing glu- 

 cose. The ash from this amount of pure fruit juice or pure fruit 

 products will contain only traces of sulphates and chlorids, while that 

 from glucose products will contain determinable amounts of either 

 sulphates or chlorids or both, depending upon the processes of manu- 

 facture of the glucose. If a complete ash analysis is to be made, the 

 directions given in the official methods b may be followed. 



DETERMINATION OF TOTAL ACIDS. 



Ten grams of the juice, fresh fruit, or fruit product, or 25 cc. of 

 the solution of jelly are diluted with boiling distilled water to about 

 250 cc. In the case of fruit pulp it takes some time to dissolve all the 

 acidity from the fruit cells, and it is well to boil for a minute or so in 

 order to aid the solution. A smaller volume may be employed if the 

 product is not highly colored. Add phenolphthalein and titrate the 

 acid with decinormal potassium hydroxid. Frequently with highly 

 colored products it is impossible to determine with accuracy the end 

 reaction in case phenolphthalein is used. In such cases delicate litmus 

 paper may be used to advantage, but the product must not be highly 



a Ann. der Chem., 1877, 190, 1; Button's Volumetric Analysis, 8th edition, p. 155. 

 b U. S. Dept. of Agr., Div. of Chem. Bui. 46, revised, p. 77. 



