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Each oil sample sent in for analysis must be accompanied by this?
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∙ 12y ago
Oil Analysis Request
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∙ 12y ago
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What are the precautions while using centrifuge machines?
while using centrifuge the sample must b kept at opposite position to each other in order to balance the machine. the lid of an centrifuge must b placed tightly to avoid any accident. must b done under the guidance of well informed person.
A sample of water was found to boil at 15C in a closed container What must have been true for this to occur?
The pressure must have been extremely low in the container.
What measurement must you make to find density of a sample of matter?
Two measurements are needed - you must find its mass and its volume. Density is mass divided by volume.
How could you predicd if a block of plastic will float in water?
The block of plastic must be less dense than the water in which it will be placed in order to float. Density is equal to mass over volume (D=m/v), so you could calculate the density of the block of plastic and of a sample of the water by dividing the weight of each sample by the respective volume of each sample. If the density of the plastic is less than the density of the water, it floats! A hint: the maximum density of fresh water occurs at 4 C∘and is equal to 1 gram per 1 milliliter. When a solute - such as salt - is added, the density of water will decrease.
What are the differences between scanning and transmission electron microscopes?
A transmission electron microscopes (TEM) can magnify a sample up to one million times. The sample must be cut extremely thin. An electron beam is directed onto the sample to be magnified and some of the electrons pass through and form a magnified image of the specimen. A scanning electron microscope (SEM) can magnify a sample up to 100,000 times. A sharply focused electron beam moves over the sample to create a magnified image of the surface. Some electrons in the beam scatter off the sample and are collected and counted by an electronic device. Each scanned point on the sample corresponds to a pixel on a television monitor; the more electrons the counting device detects, the brighter the pixel on the monitor is. As the electron beam scans over the entire sample, a complete image is displayed on the monitor. SEMs are particularly useful because they can produce three-dimensional images of the surface of objects. A SEM scans the surface of the sample bit by bit while a TEM which looks at a sample all at once. The scanning transmission electron microscope (STEM)combines elements of an SEM and a TEM and can resolve single atoms in a sample.
What are the principles of random sampling?
Each member of the population must have the same probability of being included in the sample. Equivalently, each set of elements comprising a sample must have the same probability of being selected.
What two things must be true for a sample to be useful?
they must be correct and they must be the right kind of sample
What two features must a sample have if its to accurately represent a population?
The sample must be large and random.
Why the sample should be normally distributed?
The sample should not be normally distributed.If you have a population of size N from which a random sample of size n is to be drawn, then there are NCn possible samples. Each one of these must have the same probability of being thesample. That is, the sample is uniformly distributed - not Normally.
Why should melting point tests never be repeated on the same sample?
Once a sample has been melted, it may have decomposed slightly. Contamination with a decomposed product will change the MP of the sample, so a fresh sample must always be used for each new test.
To perform Uranium-235 dating on a sample what must be true?
The sample must contain Uranium-235.
What must be true for radioactive dating to be possible with a certain sample?
The sample must contain radioactive elements.
What is a sample that that consists of everyone in the population?
It is not a sample. A sample must be a proper subset of the whole population.
How can a person get a free sample at Top Knobs Hardware?
In order to receive a free sample at Top Knobs Hardware you must go to their website and go to the free sample cart. You can get up to 3 but you must pay a 5 dollar shipping and handling fee on each one. However in return you get a coupon for 5 dollars.
What is the age limit for big fun in hull?
Toddlers to adults. Children must be accompanied by an adult and adults must be accompanied by a child. There is a special area for the under fours.
When using data from population genetics research the sample must be?
The sample must have a high probability of representing the population.
How is fat content determined by soxhlet method?
The Soxhlet method for determining crude fat content is a lengthy process requiring up to a day for a single analysis. The solvent extraction step alone takes six hours. The method is therefore not favoured for routine testing purposes in the meat industry, rather it is used as a standard reference method. As well as being used to determine the fat content of meat and meat products, the Soxhlet method can be used to determine the fat content of meat meal. In the case of meat meal, the Soxhlet method is often the method of choice as a routine test. Crude fat content is determined by extracting the fat from the sample using a solvent, then determining the weight of the fat recovered. The sample is contained in a porous thimble that allows the solvent to completely cover the sample. The thimble is contained in an extraction apparatus that enables the solvent to be recycled over and over again. This extends the contact time between the solvent and the sample and allows it time to dissolve all of the fat contained in the sample. In order for the solvent to thoroughly penetrate the sample it is necessary for the sample to be as finely comminuted as possible. Before the solvent extraction step can begin the sample must be dried. Often a moisture analysis is required as well as a fat analysis and this can be achieved by accurately weighting the sample after drying and before extraction, as well as before drying. If a moisture analysis is not required the sample need only be weighed before drying and again after solvent extraction. In either case the sample must be weighed accurately on an analytical balance at each stage of the analysis. When the sample is being weighed it is important not loose any part of it including any moisture that may weep from the sample during weighting. Loss of this moisture can be avoided by weighing the sample directly into a pre-dried extraction thimble or alternatively on to a pre-dried filter paper. If a moisture analysis is required, the dried extraction thimble or filter paper also has to be pre-weighed. After weighing, the sample (in the thimble or filter paper) can be placed in the oven for drying. After drying, the sample can be placed directly into the distillation apparatus for extraction.
