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D287_8 (12b) 07-2017

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For referee testing, use the long plain form of hydrometer 1H to 10H. For field testing, use the thermal hydrometer method in test method D6822, American Petroleum Institute Manual of Petroleum Measurement Standards, chapter 9.3. Adjust the temperature of the sample in accordance with table 2 of the written standard. For field testing, test temperatures other than those listed in table 2 of the written standard may be used. The hydrometer cylinder shall be approximately the same temperature as the sample to be tested. Transfer the sample into the clean hydrometer cylinder without splashing so as to avoid the formation of air bubbles and to reduce to a minimum the evaporation of the lower boiling constituents of the more volatile samples. Warning-- extremely flammable. Vapors may cause flash fire. For the more volatile samples, transfer to the hydrometer cylinder by siphoning. Do not start the siphon by mouth. Use a rubber aspirator bulb. Remove any air bubbles formed after they have collected on the surface of the sample by touching them with a piece of clean filter paper or other suitable means before inserting the hydrometer. For field testing, make the gravity measurement directly in the sampling thief. Place the cylinder containing the sample in a vertical position in a location free from air currents. Take precautions to prevent the temperature of the sample from changing appreciably during the time necessary to complete the test. During this period, the temperature of the surrounding medium should not change more than 5 degrees Fahrenheit, 2 degrees Celsius. Lower the hydrometer gently into the sample. And when it has settled, depress it about two scale divisions into the liquid, and then release it. Keep the rest of the stem dry, as unnecessary liquid on the stem changes the effective weight of the instrument, and so affects the reading obtained. With samples of low viscosity, a slight spin imparted to the instrument on releasing assists it in bringing it to rest, floating freely away from the walls of the hydrometer cylinder. Allow sufficient time for the hydrometer to become completely stationary, and for all air bubbles to come to the surface. This is particularly necessary in the case of the more viscous samples. When the hydrometer has come to rest floating freely, and the temperature of the sample is constant to 0.2 degrees Fahrenheit, 0.1 degrees Celsius, read the hydrometer to the nearest scale division. The correct reading is that point on a hydrometer scale at which the surface of the liquid cuts the scale. Determine this point by placing the eye slightly below the level of the liquid and slowly raising it until the surface first seen as a distorted ellipse appears to become a straight line cutting the hydrometer scale. To make a reading with nontransparent liquids, observe the point on a hydrometer scale to which the sample rises above its main surface, placing the eye slightly above the plane surface of the liquid. This reading requires a correction. Determine this correction for the particular hydrometer in use by observing the height above the main surface of the liquid to which the sample rises on the hydrometer scale when the hydrometer in question is immersed in a transparent liquid having a surface tension similar to that of a sample under test. Observe the temperature of the sample to the nearest 0.25 degrees Fahrenheit, 0.1 degrees Celsius, immediately before and after the observation of the gravity. The liquid in the cylinder being thoroughly, but cautiously, stirred with a thermometer, note 2 of the written standard, and the whole of the mercury thread being immersed. Should these temperature readings differ by more than 1 degree Fahrenheit, 0.5 degrees Celsius, repeat the temperature and gravity observations when the temperature of the sample has become more stable. Record the mean of the thermometer reading before and after the final hydrometer reading to the nearest 1 degree Fahrenheit as the temperature of the test. When thermal hydrometers are used, stir the sample by carefully raising and lowering the hydrometer. It is satisfactory in this case to read the thermometer scale after the hydrometer reading has been observed. Read the thermometer to the nearest 1 degree Fahrenheit, 0.5 degrees Celsius.

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Duration: 4 minutes and 55 seconds
Language: English
License: Dotsub - Standard License
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Posted by: abuckmaster on Aug 22, 2018

D287_8 (12b) 07-2017

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