Continuous agitation, method

Catalyst Y-G was prepared in conformity with the spray-drying method of Yates and Garland 27). Ni(N03)2 was dissolved in a small amount of distilled water, whereupon acetone and the requisite amount of aerosil were successively added to it. The slurry was transferred to an atomizer and sprayed with continuous agitation. The spray was directed to a glass surface and the particles adhering to this surface were dried by leading a stream of air over them. 

There are four methods of agitation Intermittent, minimal, continuous, and stand development which will be discussed in its own section below. In order to obtain negatives with the highest degree of edge sharpness and contrast of fine detail, intermittent, minimal, or stand development must be used. Continuous agitation should be avoided. 

Continuous Agitation This method is especially popular among those using JOBO rotary processors. The film is agitated non-stop for the full time of development. The direction of agitation should be varied to avoid streaks or patterns on the film. Development time should be reduced by 20%. 

Technique of Water Bath Development The overall method for water bath development is to immerse the film in the developer for two to three minutes with continuous agitation in a tray. The film is then moved to the plain water or 3% sodium sulfite bath. It should be completely immersed in the water bath and left motionless for two to three minutes then moved back to the developer. The entire procedure is repeated as many times as necessary using a green safelight with a 15-watt bulb to check the progress of development. Turn the light on briefly after each immersion in the water bath and hold the negative up to it at a distance of three to four feet for 20 seconds or less. 

For this method to be effective it is important to monitor the time exactly. The paper should be immersed for 60 seconds with continuous agitation, drained for 15 seconds, and immediately transferred to a fresh water bath, preferably with running water. Excess time in the fixer beyond 60 seconds allows by-products to infiltrate the emulsion negating any advantage of the method. 

Most cells do not readily grow in suspension, and so this method has limited applicability. However, erythropoietic cells (lymphocytes, hybridomas, and erythroleukaemia cells) show no tendency to adhere to glass or plastic surfaces and will survive if allowed to sit on the bottom of a tube, dish or bottle covered with a shallow layer of medium. Other cells that are grown in suspension have been selected on the basis that they show poor adhesion to the substratum and they continue to grow if maintained in suspension. If not continuously agitated they will, however, settle down and adhere to the substratum. With some cells it is sufficient to maintain them in roller bottles rotating at about 2 r.p.m. but in general special suspension... 

Coacervation Phase Encapsulation by coacervation is the one of the more popular methods commonly studied. The process consists of three steps carried out under continuous agitation [43] ... 

A rapid and low cost method was developed for direct analysis of residual monomer concentration of acrylamide from inverse-emulsion reactions. Inverse-emulsion polymerisations involve the dispersion of a water-soluble monomer in aqueous solution in a continuous organic phase. The addition of a low-medium hydrophilic-lyophilic balance steric stabiliser and continuous agitation is required to maintain emulsification. 19 refs. 

Once an adequate suspension has been achieved it is then essential to keep that suspension operational whilst treating the metal components. The ideal method is to use a continuously agitated system which does not allow settlement but is not so agitated as to cause bubbling, especially with water-based materials. 

Transflectance is not likely to be more successful than transmittance for analysis of milk by NIR, because the surface presented to the instrument will be changing in composition, due to the progressive changes in fat content. Transmittance or reflectance of the sample in a large cell, with continuous agitation is the recommended method of sample presentation for NIR analysis of milk, or any other type of liquid sample containing suspended material that is liable to settling at the bottom or surface of the cell. 

The two procedures primarily used for continuous nitration are the semicontinuous method developed by Bofors-Nobel Chematur of Sweden and the continuous method of Hercules Powder Co. in the United States. The latter process, which uses a multiple cascade system for nitration and a continuous wringing operation, increases safety, reduces the personnel involved, provides a substantial reduction in pollutants, and increases the uniformity of the product. The cellulose is automatically and continuously fed into the first of a series of pots at a controlled rate. It falls into the slurry of acid and nitrocellulose and is submerged immediately by a turbine-type agitator. The acid is deflvered to the pots from tanks at a rate controlled by appropriate instmmentation based on the desired acid to cellulose ratio. The slurry flows successively by gravity from the first to the last of the nitration vessels through under- and overflow weirs to ensure adequate retention time during nitration. The overflow from the last pot is fully nitrated cellulose. 

Recent Developments. A considerable amount of cellulose acetate is manufactured by the batch process, as described previously. In order to reduce production costs, efforts have been made to develop a continuous process that includes continuous activation, acetylation, hydrolysis, and precipitation. In this process, the reaction mixture, ie, cellulose, anhydride, catalyst, and solvent, pass continuously through a number of successive reaction zones, each of which is agitated (92,93). In a similar process, the reaction mass is passed through tubular zones in which the mixture is forced through screens of successively small openings to homogenize the mixture effectively (94). Other similar methods for continuous acetylation of cellulose have been described (95,96). 

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