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Previous Next The best candle and soap tips online! If this gum tube is sufficiently elastic, and the wire on the clip Btiff enough, we need not fear that the tube when not in use will permit even one drop of liquid to flow out. IAig. 3 shows the burette provided with India-rubber tubes and clips. When the burette "13 idle and filled with the liquid, as is often the case in techr.ical operations, where experiments are so often repeated, and to be always on hand, it should then be closed above, that no evaporation may take place. Such a stopper can be easily replaced by a toy marble. That these marbles may fit more tightly, the burette has a facet-like opening, but a conical glass plug may serve this purpose better; such stoppers tre tighter and are sufficient to close it. "When as in soap manufactories alkalies are mostly to be investigated, one burette is amply sufficient for the acid, but it is a great convenience to place a second burette with a normal potash solution along-side of it. Thus a hasty analysis might be easily rectified by adding aikali to the red titrated liquid until it again assumed a pure blue, and taking the used cubic centimetres of alkali from those of the acid. The two burettes represented in Fig. 3 serve best for this purpose. But besides this it is best in case of 172 TECHNICAL TBEATISE OUT SOAP AND CAMDL3S. ALKALIMETRY. 173 breaking one to have several on hand, especially in places where it is impossible to obtain a new one at once. The burette ready for immediate and continuous use is represented by Fig. 5. THE PIPETTE. This very useful instrument is also a straight glass tube, which, excej t about 40 millimetres (1.57 inch) at its upper end and 5 millimetres (0.20 inch) at its lower end, is divided in its entire length into T'o or £ cubic centimetres (0.027 or 0.054 fluidrachm). Pipettes which hold 20 cubic centimetres (5.40 fluidrachma) are chosen of a somewhat wider diameter BO that they may not be too long, and then they are commonly divided into £ cubic centimetres (0.054 fliri-drachra). In soap manufactories two pipettes are usually sufficient for all purposes, divided in T'tf or £ cubic centimetres (0.027 or 0.054 fluidrachm), and of 10 cubic centimetres (2.7 fluidrachms) capacity. For use, the pipette is filled somewhat above the 0 degree, by a gentle suction, while the point is dipped into the liquid and then qubkly closed with the moistened ball of the index linger of the right band. By moving the finger slightly BO much of the liquid is permitted to run out until it stands precisely at 0. In order to notice this more plainly, the pipette is held against; & light surface. The lowest point of the convex segment nust just touch the division line. To let the drops fall off easily and be as small as possible, the point of the pipette ie covered with paraffin. In general the work with the pipette is more convenient than with the burette. It is held perpendicularly in the right hand, taking hold of the beaker with the left hand, or, what is still better, a large porcelain cup, letting so mush flow out of the pipette until the liquor appears of the desired color. Pipettes ate useful instruments to quickly measure off certain larger or smaller quantities of liquid, to which end a systematic series of all sizes should be on hand of 1,2,5,10,20,50, and 100 cubic centimetres. The smaller, from 1 to 20 cubic centimetres, have the shape shown in Fig. 6. The body has Buch a diameter that the pipette may be inserted into a wide-mouthed bottle to withdraw the liquid therefrom. The larger pipettes receive either the shape as in Fig. 7, or Fig. 8; Fig. 7. Fi- (J. the former are leBs' liable to break, but the latter need not be so long. The upper, thinner part, the stem, has at a cer- 174 TECHNICAL TREATISE ON SOAP AND CANDLES. ALKALIMETRY. 175 tain part the mark for the contents for which the pipette is arranged. In emptying it the pipette is permitted to run out completely, and it is well to hold its point against the moist side of the receiving vessel, from which the drop hanging on the point is removed, or we touch with the point the surface of the poured-out liquid. The large pipettes permit in many cases a great saving of labor. Supposing we would ascertain several ingredients in one lye (alkali, chlorides, sulphates, etc.), in separate operations, then this iye is brought into a measured glass which holdfi about 500 cubic centimetres (16.9 fl. oza.) up to the mark, when by means of a pipette 100 cubic centimetres (3.38 Fig. 9. Fig. 10. ti. ozs.Jare Uken from it. We have then accurately the fifth part of the matter cortainedin the entire liquid, for instance, the alkali, which still leaves £ for testing for chlorates and sulphates, etc. FLASKS. Measure-flasks are of very extended application ; they are used of all sizes, from 100 cubic centimetres (3.38 fl. oas.) to the litre or 1000 cubic centimetres (33.8 fl. ozs.). The latter and also the 500 cubic centimetre (16.9 fl. ozs.) flask, which is equal to $ kilogramme (1.1 lb.), are most often used. They serve for measuring greater quantities of liquids than the Fig. 11. Previous Next
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