FOODS 97 



buckwheat flour, flaked rice, ground rice, rice flour, hominy 

 (split maize). The proteid varies in the different cereals. 

 Wheat flour has the largest proportion of gluten, and 

 therefore makes the best bread. Cane sugar is found in 

 all cereals. 



The analysis of these consists in estimating the moisture, 

 ash, fat, phosphoric acid, total nitrogen, and proteids ; 

 sugar, starch and dextrin, cellulose, extract and acidity, 

 and true albuminoids. 



Phosphoric Acid. Dissolve ash in diluted HC1, boil and 

 filter. Precipitate lime with Am 2 C 2 ,, filter after heating 

 on water-bath for one hour, and precipitate phosphoric acid 

 from filtrate with AmCl, AmOH, and MgCl 2 . Stand for 

 twelve hours, filter, dry, ignite, and weigh as magnesium 

 pyrophosphate Mg 2 P 2 7 . 



Sugar, Starch and Dextrin. Take 5 grm., and boil with 

 250 c.c. aqua and 50 c.c. N/i HC1 under an invert condenser 

 for six hours. If hydrolysis of starch is complete, a drop 

 of the solution will give no blue colour with iodine solution. 

 Neutralize with 50 c.c. N/i NaOH, filter into a litre flask, 

 and with washings make up to the mark. Estimate with 

 Fehling's solution, either volumetrically or gravimetrically. 

 The Pavy-Fehling method is more reliable than the ordinary 

 way. Pavy's solution is made from Fehling's thus : 

 120 c.c. of Fehling are taken, and 300 c.c. strong AmOH 

 (sp. gr. o-88o) and 400 c.c. NaOH solution (12 per cent) 

 are added, and the volume is made up to 1 litre ; 100 c.c. 

 of this solution has the same oxidizing effect on glucose as 

 10 c.c. of ordinary Fehling solution, that is, 100 c.c === 0-05 

 grm. glucose. The cuprous oxide is not precipitated in 

 the presence of ammonia, and the titration is continued 

 until the solution is colourless. In working, take a 300 c.c. 

 boiling-flask fitted with a two-holed stopper. Through one 

 hole goes the nose of the burette containing the dilute sugar 

 solution, and through the other a tube to lead away the 

 ammonia ; 50 c.c. of the Pavy solution are taken in the 

 flask and brought to the boil. The sugar solution is then 

 run in slowly from the burette till the blue colour is dis- 

 charged. To convert glucose to starch X 0-9. 



Adulterations. Talc, gypsum, French chalk ; substitu- 

 tion ; blending ; bleaching with NO 2 (also O 3 , SO 2 , SO 3 , 



7 



