_In liquid extracts_, the thorough mixing of the liquid is of the greatest importance. Most extracts contain a portion of “difficultly soluble” tannins (see p. 297), which slowly settle to the bottom, or adhere to the sides of the cask; from which such expedients as merely rolling a full cask are quite inefficient to dislodge them. In fact nothing but taking the heads out of a sufficient number of casks, and actually stirring them with a suitable plunger, which should be specially applied to the sides and bottom, or emptying the entire contents of the casks into a tank in which the whole can be adequately mixed, is really thoroughly reliable, though at times it is necessary to be content with less satisfactory methods. In any case, when it is probable that samples must be submitted to more than one chemist, the whole should be drawn at once, thoroughly mixed and divided, and sealed in separate bottles, and in dividing a sample the same care must be taken to ensure complete mixture, as in drawing the original sample. _Solid and pasty extracts_, such as quebracho, cutch and gambier, are still more difficult to sample fairly, as the outside is almost invariably much drier than the interior. Generally the only way is to select such portions as are thought fairly to represent the bulk, to chop them into moderately small pieces, mix and seal in an air-tight tin, leaving it to the chemist to draw from these the smaller sample required for analysis. Gambier is best sampled with a tubular tool like a cork-borer, designed by Mr. Kathreiner, Fig. 63, which should be passed completely through the bale, or the cylindrical sample of gambier cannot be withdrawn. The same tool may also be used for sampling sumach in bags, if the damage to the bag is not objected to. If such a tool is not available, the only fair way to sample gambier is to cut slices completely through the bale with a clean fleshing knife. In any case it is of the utmost importance that the sample once drawn, should be mixed as rapidly as possible, and at once enclosed in an _air-tight_ box or jar, sealed and labelled. [Illustration: FIG. 63.--Kathreiner’s Sampling Tools. A, strong cross-handle; B, guard-disc; C C´, brass tube sharpened at C´; D, brass or wooden plunger.] _Dry tanning materials_, such as bark and valonia, require judgment in selecting samples which fairly represent bulk. If they are of a nature which do not readily separate into dust and fibre, a good method is to grind a sufficient quantity in an ordinary bark-mill, and after well mixing, to draw the sample from the ground portion. In other cases it is best to empty a sufficient number of bags one upon another in layers on a smooth floor, and to take out a section down to the floor. In such materials as valonia and divi-divi, the dust or beard is usually much stronger than the average of the pods or cups.