315 



This latter operation, though comparatively easy with ethereous 

 and alcoholic liquids, often engenders great difficulties with 

 aqueous extracts on account of the presence of colloidal matters, as 

 albumin and gum. It is therefore better to first try a small 

 quantity, and if filtering is found practicable, to give the whole 

 into the displacement apparatus and to wash with water, until the 

 latter passes ofi" clear. Any decomposing efiect of heat has to be 

 avoided by performing the operation in a cool place. 



If, on the contrary, filtering through paper should prove 

 incomplete and slow, it is necessary to strain the mass through 

 miller's gauze (silk bolting cloth), not through linen, calico, or 

 flannel, because the meshes of these latter fabrics would soon 

 become filled up by swelling, and so prevent the liquid from pass- 

 ing through. Spread a circular piece of the silk gauze (preferably 

 of No. 10 to 13) over a wide glass jar, pi'ess it in the middle 

 slightly into the vessel, secure the part of the gauze resting on 

 the edges by means of a wide j^orcelain ring, pour the contents of 

 the flask into the bag-like cavity, and rinse the flask with a little 

 water. After the liquid has ceased dripping, take hold of the 

 cloth, tie it together close over the contents with pack-thread, and 

 press out as much liquid as possible. Or use a small bookbinder's 

 press, the side wedges (those parts that come in contact with the 

 liquid) of which are covered with glass or porcelain plates. Again, 

 mix the pressed-out substance in a porcelain dish with water to a 

 pulp, strain and press, and I'epeat these operations once more. 

 Mix the whole of the liquids well together, and allow them to 

 subside in a cool place. 



An amount of starch or inulin, surpassing mere ti'aces, may be 

 separated from the vegetable substance in a merely mechanical 

 way, i.e., by kneading. A partial separation is even effected in 

 straining through gauze, but may be considerably improved in 

 case of anj'' starch or inulin having been observed in the first 

 liquid by kneading the substance after the second pressing, and 

 after the gauze-bag containing it has been tied as before, under 

 water and for a considerable time, adding the milky water to the 

 other liquids and kneading again under fresh water until the 

 substance is entirely exhausted. From the tmited liquids, starch 

 or inulin subside gradually. Filter, or, if impracticable, decant 

 the clear liquid, collect the sediment of starch or iniilin on a 

 filter, dry at 110°, and weigh. 



By filtering the aqueous extract in the displacement a^iparatus, 

 starch or inulin are, of course, left in the remnant. The presence 

 of starch is easily ascertained by shaking a small quantity of the 

 substance with solution of iodine, when it will assume a violet 

 or blue colour. The presence of inulin can only be ascertained by 

 kneading. Starch and inulin have, as yet, not been observed in 

 the some plant; and, whereas the former occurs in widely 



