Test, testing staining

The standard and test stains must be compared immediately as they fade out on retaining. 

Preparation of the test staining solution 0.5 g of C.L Solvent Red 27, for example Oil Red O (Aldrich, Fluka, Sigma), in the literature recommended as Oil Red 5B, is wetted with a little methanol and then dissolved in 50 ml m-cresol. 

Fig. I7.S. Blocking and neutralization tests. In the blocking test, positive staining can be prevented by pre-incubation of the tissue with the specific antibody, whereas in the neutralization test staining is prevented by adding pure antigen to the immuno-reactants prior to incubation with the tissue.

A certain part of some stains will also be removed by water or the detersive parts of the formulation and the degree of bleachable stain removal achieved is, to a first approximation, the sum of the contribution from the bleach system and that from the other components. The relative contributions depend on the nature and history of the stain. Test stains, whether produced in-house or purchased from a commercial supplier, that have not been aged realistically tend to be more easily removed via the action of components other than the bleaching system. 

Because test stains can often be artificially fixed to the fabric substrate when manufactured, by using mechanisms such as increased water hardness, it is recommended that the degree of removal by nonoxidative mechanisms is always evaluated first (i.e., by undertaking a preliminary wash test with the base detergent with bleach absent) in order to get a true measure of the relative contributions that activated and unactivated bleach... 

If the standard stains are mounted on cardboard in such a way that the lower edges are in alignment, the upper edges of the stain should then form a continuous curve. Subsequently test stains can be determined by placing the strips in alignment with the standard strips and moving the former until the upper edge of the stain coincides with the curve. 

The design of a stain-resistance test has to deal with two problems how to (1) apply the test stain to the carpet in a realistic and reproducible manner and (2) to evaluate or measure the resulting coloration of the carpet. 

Marsh s test for arsenic The arsenic-containing specimen is converted to volatile AsHs which is decomposed to a brown stain on heating. Estimation is by comparison of stains. Sb reacts similarly but the Sb stain is not soluble in NaOCl. 

The oxidation of black lead(II) sulphide to the white sulphate is a very sensitive test if the black sulphide is used as a stain on filter paper. 

Schiff s test. Dissolve about o i g. of uric acid in NsjCOj solution and pour some of this solution on to a filter-paper which has been moistened with AgNO solution a black stain of metallic silver results. 

Visual and Manual Tests. Synthetic fibers are generally mixed with other fibers to achieve a balance of properties. Acryhc staple may be blended with wool, cotton, polyester, rayon, and other synthetic fibers. Therefore, as a preliminary step, the yam or fabric must be separated into its constituent fibers. This immediately estabUshes whether the fiber is a continuous filament or staple product. Staple length, brightness, and breaking strength wet and dry are all usehil tests that can be done in a cursory examination. A more critical identification can be made by a set of simple manual procedures based on burning, staining, solubiUty, density deterrnination, and microscopical examination. 

Detecting the presence of small, even invisible, amounts of blood is routine. Physical characteristics of dried stains give minimal information, however, as dried blood can take on many hues. Many of the chemical tests for the presence of blood rely on the catalytic peroxidase activity of heme (56,57). Minute quantities of blood catalyze oxidation reactions between colorless materials, eg, phenolphthalein, luco malachite green, luminol, etc, to colored or luminescent ones. The oxidant is typically hydrogen peroxide or sodium perborate (see Automated instrumentation,hematology). 

The characteristics of interior paints that require testing and analysis include hiding and appearance, package stabiHty, adhesion, spatter resistance, flow and leveling, color and sheen uniformity, touch-up, stain removal, burnish resistance, and block and print resistance. A popular test that assesses the wet abrasion resistance of an interior paint is to measure its scmb resistance. A mechanical device is used to scmb a paint film of a specified thickness with a standard bmsh and abrasive cleanser suspension. The number of scmb cycles (back and forth movements of the weighted bmsh) at various end points (first cut through, or 50% removal of the film) is then recorded. Scmb resistance usually holds steady or decreases slightly as PVC is increased, but drops quickly once the CPVC is exceeded in a paint formulation. 

Water-repeUent fabrics resist wetting or repel waterborne stains they pass AATCC Test Method 22 (Spray Test). 

OU-repeUent fabrics resist wetting by oUy Hquids and repel oilhorne stains. The level of performance of such fabrics is judged by AATCC Test Method 118. 

In the 3M Water/Alcohol Drop Test (41), this test is designed to provide a simple, rapid method to assess the aqueous stain resistance of substrates treated with a protective finish. 

Stain (ASTMD1328). This test measures the amount of stain on paper or other ceUulosic materials by asphalt. Variations of the cigarette paper stain procedure include the Barber stain, usually conducted at 54.4°C and 3.9 MN (400 g-force). Talc stain tests are also used. 

Sulfide content is determined by titration with standard lead nitrate solution (1 g/L). The titration is continued until a drop of the test solution on a filter paper ceases to produce a stain with a drop of lead nitrate solution. 

Abrasive. Dentifrices have the unique ability to remove extrinsic tooth stains, which are caused by agents such as berries, tea, smoking, antibiotics, and certain bacteria as they attach to the dental pellicle. These stains can be removed only by abrasive cleaning a toothbmsh alone is not adequately effective. It has been shown that only 4% of a test population were able to maintain thein teeth in an acceptably stain-free state without an abrasive and that 18% of the population were "heavy" stainers (2). However, colored materials found in dental plaque are removable without abrasives. 

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