322 METHODS OF ANALYSIS [Chap. 



27 ETHER EXTRACT.— TENTATIVE. 



Weigh 10 grams of the sample into a capsule and mix with about 30 grams of 

 sand. Heat on a water bath until the mixture appears dry and complete the dry- 

 ing in a water oven. Grind until all the lumps are broken up, and determine the 

 ether extract as directed under VIII, 10. 



28 PROTEIN.— OFFICIAL. 



Determine the nitrogen as directed under I, 18, 21 or 23, using 5 grams of the 

 sample. Multiply the result by 6.25 to obtain the amount of protein. 



29 ACIDITY.-TENTATIVE. 



Weigh 10 grams of the sample into a 200 cc. graduated flask, make up to the 

 mark with water, shake, filter through a dry paper and determine the acidity in 

 100 cc. by titration with N/10 alkali, using phenolphthalein as an indicator. Ex- 

 press the result as acetic acid. One cc. of N/10 alkali is equivalent to 0.0060 gram 

 of acetic acid. 



30 COPPER-REDUCING SUBSTANCES.-TENTATIVE. 



By Direct Inversion. 



Proceed as directed under VIII, 60, except that 10 grams of the sample, without 

 previous washing or extraction, are treated directly with 200 cc. of water and 20 cc. 

 of 25% hydrochloric acid and the solution is made up to 250 cc. after neutralizing 

 and before filtering and drawing off the aliquot. In analyses of samples contain- 

 ing starch, particular attention should be given that the amount of dextrose 

 present in the aliquot taken for the reducing sugar determination docs not exceed 

 the maximum permitted for that determination. Calculate the result in terms of 

 starch. 



31 CRUDE FIBER.— TENTATIVE. 



Transfer 8 grams of the sample (equivalent to about 2 grams of dry matter) to a 

 porcelain or glass mortar. Treat with a little hot 1.25% sulphuric acid and rub into 

 a uniform thin paste. It is absolutely essential that this paste be uniform in con- 

 sistency and entirely free from lumps. Rinse the thin mixture into a 500 cc. Erlen- 

 meyer flask, using a total volume of 200 cc. of the hot 1.25% sulphuric acid for the 

 entire operation. Proceed as directed under VIII, 68, and remove all the fat, pre- 

 vious to weighing of the crude fiber, by repeated washings of the dry fiber with 

 ether. 



32 COLORING MATTERS.— TENTATIVE. 

 Proceed as directed under XI. 



33 PRESERVATIVES.-TENTATIVE. 

 Proceed as directed under X. 



TOMATO PRODUCTS. 



34 PREPARATION OF SAMPLE.-TENTATIVE. 



Shake the package and contents thoroughly to incorporate any sediment, then 

 transfer the entire contents of the container to a large glass or porcelain dish and 

 mix thoroughly, continuing the stirring for at least 1 minute. Transfer the well 

 mixed sample to a glass-stoppered container and shake or stir thoroughly each time 

 before removing portions for analysis. 



