Frequent filter

Place 50 ml. of concentrated ammonia solution (sp. gr. 0 88) in a 200 ml. conical flask (1) and cool in ice. Add 12 1 g. (10 0 ml.) of redistilled benzoyl chloride (Section IV.185) drop by drop from a separatory funnel whilst shaking the flask frequently. Filter off the precipitated benzamide, wash with a little cold water, and recrystallise from hot water (about 50 ml.) dry upon filter paper in the air (2). The yield of pure benzamide, m.p. 129°, is 9 g. 

C.F. van Duin et al (Ref 6) reviewed all of the methods previously used, and described the following method of prepn Mix 1 Og of finely pulverized trinitro-m-anisidine (or phenetidine) with 80ml of coned ammonia (d 0 90g/cc) and leave for 24 hours at room temp. Shake frequently. Filter, wash the ppt with w to remove the ammonia, and boil with ale to remove traces of non-reacted TNAnis or TNPhenet. The mp of the product should be around 285°, but it rises slightly to 287—288° if the product is re-crystd from gl acet ac (See also Ref 1, pp 60,... 

A choice of a filter with the correct membrane pore size can prevent the shift in polish rate. The pore size chosen must be significantly larger than the slurry particle sizes. For example, if the mean of the slurry particle size is 1000 A, the pore size should be a few microns, so that no normal sized particles will be filtered out. Frequent filter changes can prevent filter clogging. 

Sulfur shipped as a solid frequently becomes contaminated with dirt and scale during shipping and handling. In areas of the world where solid sulfur is still handled, molten sulfur is frequently filtered prior to use as an alternative to, or in combination with, hot gas purification. Since the early 1970s, most sulfur used in the United States and Europe has been shipped and handled as a liquid containing very low ash concentrations, typically <0.005%. Using this type of raw material, neither sulfur filtration nor hot gas purification are essential, and are rarely used. 

Calcium. — Digest 20 gm. of copper oxide with a mixture of 5 cc. of nitric acid and 95 cc. of water for about fifteen minutes, shaking frequently filter, precipitate the copper in the filtrate completely by passing hydrogen sulphide gas, and filter again. Evaporate the filtrate on the water-bath to about 20 cc., add ammonia water in excess, filter once more, and to the filtrate add ammonium oxalate solution. No immediate turbidity should be produced. 

Specificity is an ever-present criterion because there are indeed few analytical techniques that detect single species without careful tuning, Frequently, filtering techniques must be used as a means of narrowing the range of detection. See Infrared Radiation and Ultraviolet Spectrometers. 

Add 4 ml of 3 % H202 solution, heat nearly to boiling (to oxidize arsenite to arsenate), cool and allow to stand for 10 minutes shake frequently. Filter. 

As diesel ages a fine sediment and gum forms in the fuel brought about by the reaction of diesel components with oxygen from the air. The fine sediment and gum will block fuel filters, leading to fuel starvation and engine failure. Frequent filter changes are then... 

Direct flow filtration has certain Umitations. The flux (filtration flow rate per unit membrane area) decreases over time as the process continues because the filtering media is loaded with more contaminant particles, as illustrated in Figure 14.1. Moreover, when the concentration of the contaminant in the feed stream is high, the filtering media must be replaced very frequently, which can be economically impractical. Also when the contaminant matter to be separated is small in size, requiring ultrafiltration or reverse osmosis membranes with much smaller pores, then direct filtration is less feasible as the flux declines very rapidly over time, again requiring frequent filter replacement. 

Figure 4.4.5 Concentration of Cd (log scale) in frequent filtered (O) and unfiltered (total) ( ) spot samples of water compared with time weighted average concentrations measured using the DOT open pore sampler deployed for overlapping periods of 7, 14 and 28 days in the River Meuse (NL)...

Mix the oxide of antimony and acid tartrate of potash with sufficient distilled water to form a paste, and set aside for twenty-four hours then add the remainder of the water, and boil for a quarter of an hour, stirring frequently. Filter, and set aside the clear liquid which contains the tar tarated antimony, to crystallize. Pour off the mother liquor, evaporate to one third, and set aside, that more crystals may form. Dry the crystals (tartarated antimony) on filtering paper at the temperature of the air. 

Macerate the aloes and the myrrh in the spirit and the water, previously mixed, for fourteen days in a closed vessel, ajid shake frequently. Filter and add sufficient proof spirit to make one pint. 

Some plants will dedicate a significant portion of the filter area to drying and will block off sprays or drips in this area. The intent is to reduce the Oil in Wax to increase yield and possibly debottleneck wax recovery. An unintended consequence is that the vacuum that remains on in this section will pull the wax cake into the filter cloth, accelerating the filter fouling which will reduce wash acceptance and increase oil in wax. It will also require more frequent filter washing which will reduce plant throughput. These competing factors must be balanced by the manufacturer to achieve the optimum filter performance. 

When the lack of an industry-wide filtration standard is coupled with a tendency to purchase filters on the basis of price, it is not surprising that there is a general tendency to undersize amine filters (Ballard and von Phul, 1991). A severely undersized filter that requires frequent filter element change out can seriously impact operator acceptance and lead to long-term operability and maintenance problems. Therefore, the designer is urged to size amine filters conservatively, as a filter that is too large is far superior to one that is too small. Table 3-7 summarizes recommendations from various sources. The relative merits of various filter selections follow. 

---