178 METHODS OF ANALYSIS [Chap. 



the washings to 1000 cc. Transfer the insoluble residue to an evaporating dish, dry 

 and weigh. If it is desired to determine the alcohol precipitate, 18, cool the filtrate, 

 make up to a definite volume and reserve for this determination. 



5 Indirect Method. — Tentative. 



Transfer 25 grams of the fruit product to a 250-500 cc. graduated flask, the size 

 of the flask depending upon the volume of insoluble matter present, add water, 

 shake thoroughly and make up to volume. Allow to settle and either filter or decant 

 the supernatant liquid. Determine the soluble solids in an aliquot, as directed in 

 3 (a). The fruit must be macerated thoroughly; the use of a mechanical shaker is 

 advisable. The percentage of insoluble solids is the difference between the per- 

 centage of the total solids and the percentage of soluble solids. 



6 TOTAL ASH.— OFFICLO-. 



Determine the ash as directed under VIII, 4, using 50 cc. of the solution of the 

 jelly or diluted sirup, 1 (b), evaporated to dryness, or 25 grams of juice or of fresh 

 or canned fruit, or 10 grams of jam, marmalade, preserves, or dried fruit. 



7 ALKALINITY OF THE ASH.— TENTATIVE. 



Into the platinum dish containing the ash introduce a measured excess of N/5 

 nitric acid, heat to boiling, cool 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 

 N/10 potassium or sodium hydroxid. Express the result as the number of cc. of 

 N/10 acid required to neutralize the ash from 100 grams of the sample. 



8 SULPHATE AND CHLORID.-TENTATIVE. 



Wash the solution of the ash, obtained in 7, into a 50 cc. flask and make up to the 

 mark with water. Evaporate 25 cc. of this solution to dryness several times with con- 

 centrated hydrochloric acid, take up the final residue in a small amount of hot water, 

 filter, wash the paper with hot water, acidify the filtrate with a few drops of hydro- 

 chloric acid and determine the sulphate by precipitation with barium chlorid 

 solution. From the weight of barium sulphate calculate the sulphate present as 

 per cent of potassium sulphate. 



In the other portion of the solution determine the chlorin as directed under III, 15. 

 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 solu- 

 tion for the titration. Calculate the chlorin as per cent of sodium chlorid. 



9 TOTAL ACIDITY.— TENTATIVE. 



Dilute 25 cc. of the solution of jelly or diluted sirup, 1 (b), or 10 grams of juice or 

 fresh fruit, with recently boiled water to about 250 cc, or less if the sample be not 

 highly colored; titrate the acid with N/10 alkali, using phenolphthalein as an in- 

 dicator. In the case of highly colored products employ azolitmin solution or phenol- 

 phthalein powder [XVI, 25] on a spot plate instead of phenolphthalein solution. 

 Calculate the results as malic, citric or tartaric acid, specifying the acid used and 

 expressing the results in grams per 100 cc. 



10 VOLATILE ACIDS.— TENTATIVE. 



Dissolve 10 grams of tlie sample, dilute to 25 cc. and distil in a current of steam, 

 as directed under XVI, 27. Each cc. of N/10 alkali is equivalent to 0.0060 gram of 

 acetic acid. 



