The name flour is usually given to the product obtained by grinding wheat and removing the bran, or woody portion of the grain, by sifting or bolting. Its constituents are starch, dextrine, cellulose, and sugar (carbohydrates), the nitrogenous compounds albumen, gliadin, mucin, fibrin, and cerealin, and fat, mineral substances and water. Upon kneading flour with water, and removing the starch and soluble matters by repeated washing, an adhesive body termed _gluten_ remains behind. This is chiefly composed of gliadin, mucin, and fibrin. According to Wanklyn,[50] the general composition of flour is:-- Per cent. Water 16·5 Fat 1·5 Gluten 12·0 Modified starch 3·5 Vegetable albumen 1·0 Starch granules 64·8 Ash 0·7 The average of numerous analyses of American flour examined by the Department of Agriculture gave:-- Per cent. Water 11·67 Fat 1·25 Sugar 1·91 Dextrine 1·79 Starch 71·72 Soluble albuminoids 2·80 Insoluble „ 7·90 Total „ 10·70 Ash 0·54 The composition of the ash of flour from Minnesota wheat (1883), is as follows:-- Per cent. Insoluble 0·98 Phosphoric acid 49·63 Potassa 31·54 Magnesia 9·05 Lime 5·87 Soda 2·93 ANALYSIS OF FLOUR. The following are the determinations generally required in the proximate analysis of flour:-- _Water._--Two or three grammes of the sample are weighed in a tared platinum dish, and heated in an air bath, until constant weight is obtained. The proportion of water should not exceed 17 per cent. _Starch._--A small amount of the flour is placed in a flask, connected with an ascending Liebig’s condenser, and boiled for several hours with water slightly acidulated with sulphuric acid. Any remaining excess of acid is then neutralised with sodium hydroxide; the solution is considerably diluted, and the glucose formed, estimated by means of Fehling’s solution (see p. 111). 100 parts of glucose represent 90 parts of starch. _Fat._--The inconsiderable proportion of fat in flour is best determined by exhausting the dried sample with ether and evaporating the solution.