_Linseed and rye meals._--If linseed meal is moistened with an aqueous solution containing 14 per cent. of potassa and examined under the microscope, numerous minute characteristic granules, smaller than the grains of potato-starch, are observed. These possess a vitreous appearance, sometimes a reddish color, and usually form in squares or very regular rectangles. The test is equally applicable to bread. The detection of linseed and rye meals is simultaneously effected by exhausting the suspected flour with ether, then filtering the solution and allowing it to evaporate. If the flour contains rye, the oil left by the evaporation, when heated with a solution of mercury in concentrated nitric acid, is converted into a solid substance having a fine red color; but it remains unaltered, if entirely due to linseed. In case the oil becomes solidified, the mercury salt present should be removed by washing with water, the residue taken up with boiling alcohol of 36° B. and the solution filtered: upon evaporating the alcoholic filtrate, a residue is obtained consisting of the linseed oil present. _Buckwheat._--Flour adulterated with buckwheat is less soft to the touch, does not pack as easily, and passes more readily through a sieve than pure wheaten flour. It presents, here and there, blackish particles, due to the perisperm of the grain, and has a dirty-white color. As previously remarked, the gluten obtained from a mixture of buckwheat and wheaten flour possesses a grey or even a black color. The starch furnished by buckwheat flour exhibits polyhedral agglomerations, analogous to those presented by corn. _Darnel._--The use of darnel in the adulteration of wheaten flour may give rise to serious sanitary results. To effect its detection, the flour to be examined is digested with alcohol of 35° B.: if the flour be pure, the alcohol remains limpid: it acquires a straw-yellow tint, due to traces of bran present, but--although a peculiar resin may be dissolved--the solution does not possess a disagreeable taste. When, on the contrary, darnel is present, the alcohol assumes a green tint, which gradually deepens, and possesses a bitter and nauseous taste; the residue, left by the evaporation of the tincture to dryness, has a greenish-yellow color, and a still more disagreeable flavor than the alcoholic solution.