"958 



FOODS AND FOOD ADULTERANTS. 



lead acetate were then added and the mixture again shaken. After allowing it to 

 settle, the clear liquid was decanted through an asbestos filter and water added to 

 supply its place. This was in turn decanted, and so on until the filter began to clog, 

 when just enough acetic acid was added to the material in the flask to turn it red. 

 Decantation and filtration were then continued till the filtrate came through color- 

 .less. Under these conditions nitrations were rapid and filtrate extremely clear. 

 The asbestos filter and contents were then placed in the flask, water enough added 

 to bring the whole to about 100 cc, and the flask placed on the steam bath for 

 three hours. At the end of this time 10 cc of concentrated HC1 were added, and 

 the heating continued three hours more. After cooling, Na^COs was added until the 

 contents of the flask became blackish. The whole was now washed into a 250 cc 

 flask and made up to the mark. Dextrose was oxidized by Allihn's method, 25 cc 

 of solution being used, and the resulting Cu. 2 O collected on a Gooch crucible, redis- 

 solved in HNO :i , converted into CuSO 4 . and the Cu determined electrolytically. 



Five samples of commercial starchy materials were examined for the purpose of 

 determining the amount of starch converted to dextrose by the method employed. 

 Three grams of material were heated on the steam bath for three hours with 200 cc 

 of water; 20 cc of HC1. (sp. gr. 1.125) were then added and the heating continued 

 three hours longer. After neutralization with Na^COa dilution to a definite volume, 

 and filtration from the slight residue, the dextrose was determined by Allihn's 

 method, the amount of Cu.^O being determined electrolytically. Duplicate samples 

 were inverted and duplicate weighings made from each inverted solution. The 

 results were as follows : 



9 



Percentage of starch in commercial starchy materials used in manufacture of cocoa prepara- 

 tions, i. e.,per cent of dextrose obtained by inversion X 0.9. 



[All samples were air-dried.] 



Starch determinations are only reliable when the conditions are held 

 rigidly exact. In order that this may be made more certain each set 

 of determinations should be accompanied by a check determination with 

 material of known dextrose-yielding power. 



Determination of fiber. The official method of the Association of Official Agricul- 

 tural Chemists' was adapted to (his work, :is follows: Two grams of material were 

 placed in a long narrow test tube with a lip, washed with" several portions of ether, 

 deeaiiting through a Gooch crucible. After evaporation of the ether, the muterial in 

 the- tube and crucible was washed into an Erlenmeyer flask with 200 cc of 1.25 per 

 cent HiSO 4 . After boiling a half hour with a reflux condensing tube, the solution was 

 filtered through a linen filter, and the residue thoroughly washed with hot \\aier; 

 while still hot, the filtrate was refiltered through a Gooch crucible, and the slight 

 residue again thoroughly washed with hot water. The material on the linen and in 

 the crucible was rinsed back into the flask with 200 cc of !.!'."> per cent NaOH, and 

 the boiling and filtration repeated. The material on the linen was then washed into 



1 r.nlletin No. 31, Cheiii. Div., U. S. Dept. of Agriculture. 



