Standard suspensions

Standard Suspension Polymerization Techniques, Appendix (1980). In Polymer-Supported Reaction in Organic Synthesis (P. Hodge and D. C. Sherington eds.), Wiley Chichester. 

Replace the standard suspension with more dilute suspensions, and note the various scale readings. Draw a calibration curve relating meter readings and the concentrations of the substance being determined. 

Now, a standard suspension is placed in one clear-glass-tube, and the unknown solution is treated exactly in an identical fashion and placed in the other clear-glass-tube. Finally, the dividing line existing between the two fields in the eye-piece (Figure 20.2) must be distinctly thin and sharp, and it must disappear when the two fields are matched properly. 

The Parr turbidimeter is an extinction type instrument, which consists of a cylinder to contain the turbid suspension, a lamp filament of fixed intensity at the base, and an adjustable plunger through which visual observation is made. Measurement is made of the depth of turbid medium necessary to extinguish the image of the lamp filament Standard suspensions are used to prepare a calibration curve, which is a plot of depdi vj. concentration. 

Narrowly classified latices are available from Dow Chemicals [134] but doubt has been expressed on the accuracy of their sizing. A 3.49 pm polystyrene latex was independently sized by electron microscopy and found to have a mean diameter of 3.40 pm [135]. This standard was used by Coulter Electronics as a standard to size other Dow latices [136] that are available from them as standard suspensions. 

These are really modifications of the earlier cup or ditch-plate procedures where filter-paper discs impregnated with the antimicrobial replace the antimicrobial-filled cups or wells. For disc tests, standard suspensions (e.g. 0.5 McFarland standard) of log phase growth cells are prepared and inoculated onto the surface of appropriate agar plates to form a lawn. Commercially available filter-paper discs containing known concentrations of antimicrobial agent (it is possible to prepare your own discs for use with novel drugs) are then placed on... 

HDgo haemolytic dose 50 the quantity of complement needed to lyse 50% of a standardized suspension of sensitized erythrocytes. 

The Microtox acute toxicity test is based upon measuring metabolic inhibition using a standard suspension of luminescent bacteria. Since bioluminescence is a direct measure of metabolic activity in these wganisms, measuring the rate of light output is a simple way to measure metabolic inhibition (toxicity). The test system has been in use for over 10 years and is the subject of many reports, reviews and application studies as well as being... 

The formazine turbidity unit is defined as the concentration of a standard suspension of formazine. Formazine is a polymeric reaction product of hydrazine sulphate and hexamethylenetetramine. The suspension formed by a reaction of 1.25 mg 1 of hydrazine sulphate and 12.5 mg 1 of hexamethylenetetramine has a turbidity of one formazine unit. Calibration by nephelometric or turbidimetric measurement is carried out so that the relation 1 FT = 1 mg 1 Si02 is valid. 

In most cases, the macroporous imprinted polymers are prepared in bulk and are then crushed and sieved. Thus, by a rather tedious procedure, irregularly broken polymers are obtained. Usual suspension polymerization is not possible with most non-covalent and even with some covalent bindings since water interferes with the binding reaction, and hampers an efficient imprinting. By using new types of stoichiometric non-covalent binding, these difficulties can be overcome and polymers can be prepared by standard suspension polymerization methods [118]. Uniformly sized particles are thus easily obtained. 

Ordinary solutions are distinguished from colloidal solutions and standard suspensions according to particle size (Table 9.1). Of course, the limits between these different classes are not perfectly defined. In particular, the upper size limit for colloidal particles is between 0.1 and 10 p,m, according to the criteria retained. 

Standard suspensions >1000 >10 Do not pass through filters, visible under a microscope, disperse in the solution with great difficulty, do not dialyze, settle very rapidly... 

Figure 3.8. Effect of 25 ug candicidin/ml upon a standard suspension of C. albicans MCrC 713. (oj Candicidin uptake, f e) candicidin-induced K leakage, candicidin-induced change in cell refractive index, (m) percentage yeasts killed, ( ) candicidin-induced inhibition of Oi uptake and candicidin-induced proton uptake...

A measurement can also be made by comparing the turbidity of the water with that of a series of dilutions of a kieselguhr standard suspension (1.00 g... 

A standard suspension polymerization process for the production of PMMA beads begins with the charging of 24.64 parts of methyl methacrylate and 0.25 parts of benzoyl peroxide to a 30°C solution containing 0.42 parts disodium phosphate, 0.02 parts monosodium phosphate, and 0.74 parts of Cyanomer A-370 (polyacrylamide resin) in 79.93 parts of deionized water. The reaction mixture is brought to 75°C and held there for 3 h. After cooling, the beads are isolated by filtration, washed with water, and dried (74). 

The concentration of the suspension density in the crystallizer is still too low for separating in a centrifuge. As mentioned in this chapter, the standard suspension densities in the crystallizers are 15-25% by mass, while centrifuges only begin to work ideally from a level of 50-60%. For this reason, the suspensions are initially preconcentrated in static prethickeners or in hydrocydones. The tail flow from this equipment is either removed from the process or partly returned to the crystallizer if dilution of the suspension that is being produced is required. In any case, part of the mother liquor has to be removed from the process in order to discharge the impurities that must not be contained in the crystallized mass from the process. 

Structured Surfactant Formulations (SSF) are close-packed three-dimensional matrices of a liquid crystalline phase that suspend insoluble pesticide materials. The active ingredient can be either solid or liquid. Additional actives and/or adjuvants can be dissolved or suspended in the formulation if desired. The main advantage of an SSF over standard suspension concentrates is that no thickening or suspending agents are required. The SSF formulation can be solvent-fiee if desired, or include an oil adjuvant built in for inqiroved efficacy. 

In comparison, a standard suspension of 12 gl of clays and pol5miers, as used in the oil industry, showed an average fluid loss of 7.2 ml and a filter cake ca. 280 pm thick. 

Based on this results, two standard suspensions were chosen for the investigation of the effect of changed process parameters on the structure formation process and therewith resulting internal granule structures (Table 11.6). 

Standard suspensions of pure Si02 were used priginally to calibrate Jackson Candle Turbidimeter, which is now used for routine work and no standards are... 

Take a number of glass bottles of the same size, shape and colour characteristics. Place the sample in one bottle and a number of standard suspensions of varying turbidities (made by suitably diluting, with distilled water, a natural turbid water standardLsed with Jackson Turbidimeter) in other bottles. Look through the sides of the bottles (sample and standards) at the same object (ruled paper or printed matter) and compare the distinctness with which the object can be seen. The turbidity of the sanijrle is equal to the turbidity of the standard that most closely produces the same interference to visual perception as the sample. 

As the number and size of particles changes with time, the standard suspensions must be frequently replaced. 

---