Automatic siphon

FIG. 1 Soxhiet extractor. For exhaustive extraction of soiid mixtures, and even of dried ieaves or seeds, the soiid is packed into a fiiter paper thimbie. Soivent vapor rises in the iarge diameter tube on the right, and condensed soivent drops onto the soiid contained in the fiiter paper thimbie, ieaches out soiubie materiai and, after initiating an automatic siphon, carries it to the boiiing flask where nonvoiatiie extracted material accumulates. The same solvent is repeatedly vaporized substances of very slight solubility can be extracted by prolonged operation. 

FIG. 2 Research-quality Soxhiet extractor. Solvent vapors from the flask rise through A and up into the condenser. As they condense the liquid just formed returns to B, where sample to be extracted is placed. (Bottom of B is sealed at C.) Liquid rises in B to level D, at which time the automatic siphon, E, starts. Extracted material accumulates in the flask as more pure liquid vaporizes to repeat the process. 

Figure 29. Automatic backwashing filter with a partial siphon.

Figure 7. Automatic backwashing filter with a partial siphon system 1-filtered water (reserve) 2-partial siphoning 3-initiation 4-restitution.

The GeMSAEC analyser can be operated either with premeasured volumes of sample and reagent, or with unmeasured but sufficient volumes. In the first case, standard automatic micropipettes can he used to load the rotors. In the second case the equipment must he modified to enable a fixed final volume to be measured and transferred to the cuvette—one way of achieving this is shown in Fig. 2.6. When the rotor is spun, the solution is forced into a transfer tube and any excess of Bquid is drained away the measuring tube is then mechanically turned through 180° and the measured volume dehvered to the cuvette. Alternatively, a series of siphons can be used to measure and transfer solutions as shown in Fig. 2.7. 

Fig. 2.7 The GeMSAEC automatic colorimeter siphon method of fixed volume sampling and transfer. Reproduced with permission of Anderson [12],...

The spent acid leaves the separator from below to flow via a siphon, the height of which can be automatically controlled, to a diluter (6) where 1-2% water is added and then to a spent add mixer (8). Dilute spent acid is pumped to tank (9), and is used for displacement of nitroglycerine from the nitrator and separator after nitration has finished. Most of the dilute acid is sent to denitration. 

Fig, 1. Automatic pipet washer. The siphon principle is utilized to empty the chamber after it has been filled to the preset point. This is a schematic diagram. Many varieties are commercially available,... 

The apparatus for Soxhiet extraction is shown in Fig. 14.5 and comprises a flask containing the solvent, a Soxhiet extractor and a reflux condenser (p. 116). The sohd to be extracted is placed in a porous thimble, made from hardened filter paper, and the solvent is heated so that its vapour flows past the thimble, condenses and fills the extractor with hot solvent to extract the solid. When the extractor is full, the solvent (together with the extracted material) siphons back into the solvent flask and the process is repeated automatically. The advantage of this procedure is that fresh solvent continually extracts the solid, which is concentrated in the flask. The disadvantage is that the compound extracted is kept at the boiling point of the solvent for a prolonged period. Soxhiet extractors come in sizes of lOmL to 5000 mL, based on the volume of solvent contained in the extractor. The procedure for using a Soxhiet extraction system is described in Box 14.2. 

This concentrate can be diluted up to 5 1 with water and then siphoned into a normal automatic car washing system. 

The crude material is put into a porous thimble at A, and the extracting solvent is placed in a flask at the bottom of the apparatus. The solvent in the flask is gently boiled and its vapour passes into the condenser via the side arm of the apparatus. Solvent vapour condenses and drips into the thimble, where the hot solvent dissolves some of the desired product present. When the level of solvent reaches the level of the top of the hne glass tube, the whole volume of solvent, containing dissolved product, siphons into the solvent flask at the bottom of the apparatus. The process continues automatically, until all the desired product has been extracted and is present, in solution, in the solvent flask. If the substances to be extracted are coloured, the process is stopped when the liquid being siphoned into the flask becomes pale or colourless. 

Any leak will stop cooling water flow automatically as the siphon flow will break hence, this is a safe system. Please refer to drawings in Chapter on Safety Management. They are not repeated here. 

Stickney, G.F. (1914). The Stickney siphon spillway and the Stickney automatic crest for dams. 

The UF membrane flux was automatically calculated daily by the control system. The results indicate the flux was typically in the 3-15 L/m. h range. Because of the siphon design, the TMP was constant at 0.11 bar (11 kPa). Periodic cleaning of the membranes was performed as required. Hypochlorite cleaning proved to be more effective than citric acid cleaning. This is as expected considering the low operating pH of the bioreactor. 

Goedhart and Opschoor (21) first applied the principle of universal calibration to calculate the Mark-Houwink constants for PVAc in THF. By measuring the intrinsic viscosity of fractions leaving the siphon of a Waters 200 GPC using an automatic capillary tube viscometer, they determined the following Mark- Houwink expression for PVAc in THF at room temperature ... 

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