Streak tests

Streak test A test to obtain a sample of powder from a specimen in order to judge its colour. It can be carried out by rubbing the specimen on a hard rough surface of neutral colour. 

Scratch tests are a common method used to identify mineral hardness relative to Mohs scale. Streak tests are often carried out on streak plates. Mineral hardness is a fundamental property of minerals and can be used to identify unknown minerals, hi the absence of comparative minerals, geologists often resort to common objects with a relatively well-established Mohs hardness number. In addition to glass (5.5), copper pennies measure 3.5, and the average human fingernail averages a Mohs hardness of 2.5. 

The true colors of some minerals can only be seen when the sample is finely powdered. Rather than grinding up a specimen, a small area is rubbed against a hard porcelain surface until a streak of the mineral is obtained. The color obtained in this streak test can be quite different from the appearance of the sample itself. For example, samples of specular hematite (the word specular refers to the mirror-like surface) have a very shiny black appearance due to the reflective nature of the naturally polished surface. The streak test reveals the true color of hematite—a red-brown. 

The brush method here the substances to be separated give a colour test with a reagent. The developed column is extruded from the tube and streaked lengthwise with a brush dipped in the test reagent the colours... 

Mice are utilized for testing antiseptics for appHcation to cuts, wounds, and incisions (339). The test bacteria, type 1 pneumococcus and hemolytic streptococcus, ate appHed to the taHs of anaesthetized mice. The tip of the taH is then dipped into the antiseptic for 2 min, after which one-half inch of the taH is removed and inserted into the peritoneal cavity and the incision is closed. If after 10 days the animals survive, the product is considered satisfactory for use as a skin antiseptic. The blood of dead animals is sampled and streaked on blood agar for confirmation of infection from the test bacteria as the cause of death. Since lack of toxicity is another requirement of a product to be appHed to wounds, this test has been combined with a toxicity test (340). 

MacConkey Streak Laboratory test for the presence of gram negative bacteria. 

Is this an Uncorrelated Hard-Disc Fluid In order to answer this question we compute a 2D CLD and test, whether the function is positive everywhere. In this case the equatorial streak can be considered pure particle scattering. 

Samples are applied as discrete spots or as streaks with capillary or micropipettes as volumes of between 1 and 20 /A. Damage to the surface must be avoided in order to achieve a regular pattern of the separated components. Appropriate reference mixtures must be applied to the same plate as the samples to assist in identifying the test components. 

Resistance Tests. Several transformants were tested for their ability to grow on all three selective media. These transformants were streaked onto nutrient agar plates containing 0.1% naphthalene, dibenzofuran, or... 

The analyst (farmer, veterinarian, laboratory scientist, or any other user) saturates a cotton tipped swab with sample tissue fluids, serum, urine, or feed extract. He then firmly places the saturated cotton swab on the surface of the appropriate growth medium previously surface streaked with the working dilution of the appropriate susceptible test organism. The test is then incubated at the proper temperature overnight and observed the next day for antimicrobial activity. If there is a zone of inhibition (no growth of the test organism) around the sample swab, the test is positive no inhibition indicates that antimicrobials are absent or below detectable levels in the sample tested. 

After 7 days, the test preparation was again shaken for 5 m at 250 rpm. A semi-quantitative determination of colony forming units (cfu) was then carried out by streaking 10 /il onto the surface of a plate of the relevant agar. 

For all the expls tested in small diam tubes, the photographs showed either breaks, similar to those described in Ref 1, or a series of small streaks in the track of the flame. 

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