The Bead Tests

Bead test procedure. Make a loop in the end of a platinum wire. Heat the Pt-wire to redness and then dip it into borax or microcosmic salt powder. A small amount of salt is coated 

The followiiig abbreviations are used in the tables h hot c cold he hot or cold ns not saturated s saturated sprs supersaturated. 

References (i) Haller, A. Girard, Ch. (1907) Memento du chimiste (Ancien agenda du Chimiste). Recueuil de tables et documents divers indispensables aux laboratoires officiels et industriels. H. Dunod E. Pinat Ed., Paris, pp. 200-210. (ii) Brush, G. (1926) Manual of Determinative Mineralogy with an Introduction on Blowpipe Analysis. John Wiley Sons, New York. 

Bead coloration Oxidizing zone Reducing zone 

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Fig. 28. The cumulative COj/CO ratio for coke bum-off on spherical catalyst beads versus combustion temperature in air (O) white amorphous silica-alumina ( ) green Cr02-containing amorphous silica-alumina (M) macroporous white catalyst. The weight (mg) of the bead tested is denoted by the numerals adjacent to the respective symbol. Dashed line represents intrinsic ratios from carbon combustion research. From Weisz (1966).

Differently colored hot and cold beads are characteristic of the compounds of different elements, and the bead test is often used to confirm other observations or to suggest a further special examination. 

The Blowpipe and its Use. — Sometimes it is not convenient to apply the bead test, nor to hold a substance directly in the flame. It is then customary to study the action of a substance when heated on charcoal in a small flame, much like the Bunsen flame and produced by... 

Thus, for years now wheels have been tested with eddy-currents with a special emphasis on finding superficial defects on the wheel s running surface. At the beginning, hand-guided probes were used which the tester slid across the surface that was to be tested. To do so, the wheel was placed on a turn table which the operator had to move manually. A higher test reliability in the transitional radius between the body and the bead wheel was achieved by using special form-fitted probes. Nonetheless, it was not possible to rule out completely that the wheel was not scanned 100 %. This test method did not allow for documentation and a subsequent reconstruction of the test. 

Boron trioxide is not particularly soluble in water but it slowly dissolves to form both dioxo(HB02)(meta) and trioxo(H3B03) (ortho) boric acids. It is a dimorphous oxide and exists as either a glassy or a crystalline solid. Boron trioxide is an acidic oxide and combines with metal oxides and hydroxides to form borates, some of which have characteristic colours—a fact utilised in analysis as the "borax bead test , cf alumina p. 150. Boric acid. H3BO3. properly called trioxoboric acid, may be prepared by adding excess hydrochloric or sulphuric acid to a hot saturated solution of borax, sodium heptaoxotetraborate, Na2B407, when the only moderately soluble boric acid separates as white flaky crystals on cooling. Boric acid is a very weak monobasic acid it is, in fact, a Lewis acid since its acidity is due to an initial acceptance of a lone pair of electrons from water rather than direct proton donation as in the case of Lowry-Bronsted acids, i.e. 

A test for secondary amines (e.g. proline) is the Chloranil test (1 drop of a 2% acetaldehyde solution in DMF, followed by one drop of a 2% solution of p-chloranil in DMF, leave for 5 mins). A positive test gives blue stained beads. 

In contrast, there are fewer limitations from the chemical point of view. The preparation of large, well-defined, libraries that involve amino acid building blocks has been demonstrated many times. Carefully optimized reaction conditions for the preparation of other mixed libraries can also ensure that each desired compound is present in sufficient amount. However, the reaction rates of some individual selectors with the activated solid support may be lower than that of others. As a result, the more reactive selectors would occupy a majority of the sites within the beads. Since the most reactive selectors may not be the most selective, testing of a slightly larger number of specifically designed CSPs may be required to reduce the effect of falsenegative results. 

In preparing immobilised cells, 1.5, 2, 3 and 6% alginate was used. By pressing them manually, the hardness and rigidity of the beads were tested. The physical criteria of the... 

Peel Strength. Samples were prepared by cutting 2.5" (63.5 mm) wide radial sections, bead to bead. The sample was then sectioned into two 1.25" (31.75 mm) radial strips, which were each cut circumferentially at the centerline of the tread resulting in four test specimens (2-SS and 2-OSS). Each sample was cut with a razor knife for a length of 1" (25.4 mm) from the skim end of the test strip, midway between the belts, to facilitate gripping the ends in the T-2000 stress-strain tester jaws. The sides of each specimen were scored midway between the belts, to a depth of 1/8" (3.175 mm) radially from the end of the gripping surface to the end of belt 2 in the shoulder area, providing a 1" wide peel section. The peel test was performed at 2"/min (50.8 mm/min) at 24°C. 

Naltrexone in combination with lactide/glycolide copolymer has been investigated (83-87). Chiang (85) reported the clinical evaluations of a bead preparation containing 70% naltrexone and 30% of a 90 10 lactide/glycolide copolymer. Each subject received a 10-mg i.v. dose of naltrexone and a 63-mg dose by subcutaneous implantation of the beads. Average plasma naltrexone levels were maintained at 0.3-0.4 ng/ml for approximately 1 month. Two out of three subjects experienced a local inflammatory reaction at the site of implantation. This unexplained problem prevented further clinical testing of... 

The estimation of f from Stokes law when the bead is similar in size to a solvent molecule represents a dubious application of a classical equation derived for a continuous medium to a molecular phenomenon. The value used for f above could be considerably in error. Hence the real test of whether or not it is justifiable to neglect the second term in Eq. (19) is to be sought in experiment. It should be remarked also that the Kirkwood-Riseman theory, including their theory of viscosity to be discussed below, has been developed on the assumption that the hydrodynamics of the molecule, like its thermodynamic interactions, are equivalent to those of a cloud distribution of independent beads. A better approximation to the actual molecule would consist of a cylinder of roughly uniform cross section bent irregularly into a random, tortuous configuration. The accuracy with which the cloud model represents the behavior of the real polymer chain can be decided at present only from analysis of experimental data. 

Fig. 1. Competition binding screens Bead/ligand compatibility test in early assay development. The beads PVT-WGA, Type A and Type B are based on polyvinyltoluene (PVT) not polyethyleneimine (PEI). PVT, polyvinyltoluene WGA, wheat germ agglutinin Ysi, yttrium silicate.

Quartz glass (silica), pyrex (borosilicates) and other household and laboratory glasses (boroaluminosilicates) owe their high chemical resistance to the (tetrahedral) network forming properties of Si, B, P and A1 (cf., the borax and phosphate bead tests in qualitative dry reactions on the salts of numerous metals). 

Although several types of fluorescent beads were proposed as a microscopic fluorescence standard 30 years ago,2 beads have not been used as a proteinembedding matrix for routine IHC on FFPE tissue. We recently tested primary coated beads ( Dynabeads, Dynal, New York) that are coated with a goat anti-mouse antibody on the surface of the beads. In the first experiment, a monoclonal antibody to cytokeratin 7 (DAKO, 50pL/34.5pg) was bound to the beads by incubating with the beads (150 pL at a concentration of 109 beads/1 pL) at 4°C in a cold room with an automatic shaker for overnight. Incubation was followed by three phosphate-buffered saline (PBS) washes,... 

PU foam crumb must also have been made from PU foam block which meet the relevant requirements. Polystyrene foam beads are considered to have passed the test if the beads cascading from the specimen consistently extinguish the gas flame (Table Vil). 

Figure 12 Test of the factorization theorem of MCT for the intermediate coherent scattering function for the bead-spring model and a range of -values indicated in the Figure. Data taken from Ref. 132 with permission.

Washing out the Tube and Titrating.—After the tube has cooled remove the boat, clamp the tube in a vertical position and replace the test tube by a clean conical flask (100-150 c.c.). Then wash out the inside of the tube with a water jet (volume of water about 10 c.c.) driving the liquid finally with small hand-bellows through the beads into the flask. Repeat this operation three times more, using 10 c.c. of water each time, wash the constricted part of the tube, transfer the contents of the test tube also to the flask, and wash out the test tube. 

Cross-reactive sensing arrays were developed to detect odors and vapors in an artificial nose manner. Solvatochromic dyes such as Nile Red are adsorbed on the surface or embedded into various polymeric or porous silica beads. The beads respond to analyte vapor by a change in fluorescence maxima or/and intensity due to changes of polarity inside the bead. A portable instrument and preliminary field test for the detection of petroleum products was recently described [106]. 

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