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The filtrate was measured and placed in a colorimetric tube, and the standard solution of sodium nitrite was separately taken up and placed in a millimeter colorimetric tube. Add milliliters of p-aminobenzenesulfonic acid solution to the standard and sample tubes, mix and let stand for one minute, then add 1.5 ml of hydrochloric acid to avoid ethylenediamine solution, add water to the mark, mix, stand still for minutes, use cm ratio The color cup is adjusted with a zero tube and the absorbance is measured at the wavelength nanometer.
Draw a comparison of the standard curves. The specific test results of this experiment are shown in the table below. The sample sample amount of nitrite is the relative error content of the phase difference. The results are discussed. Through comparison experiments, it can be seen that the sample quality of different masses has a certain influence on the measured value of nitrite. However, it can be seen from the table that the appropriate sample size is shown as the serial number, and the relative error and absolute error are compared with the serial number.
From the above experiments, it is concluded that it is feasible to appropriately scale down the sample amount in the process of determining the nitrite content in meat products. It is recommended to use the serial number method in large-scale determination. The spring tube type sound meter uses a spring tube type pressure gauge which is difficult to protect and is generally installed directly on the pressure vessel or pipe to be tested.
Because of its simple structure, convenient use and easy maintenance, it is a commonly used pressure measuring instrument in the industry. The spring tube pressure gauge can be measured as liquid, gas and steam. However, as a pressure measuring system is affected by the measured medium, it often causes one or the other problems of the pressure measuring instrument, resulting in unstable and inaccurate pressure indication.
In order to ensure that the spring tube pressure gauge is referred to as the normal operation of the instrument, reducing the occurrence of faults and prolonging the service life of the instrument, it is very important to use the pressure gauge correctly and carefully. The specific maintenance method is as follows, and the instrument should have a seal. The precision standard watch shall have a verification certificate. Frequently check the pressure-conducting pipeline, pick up Sun Zhengyuan Youbin head and welding, etc., if there is leakage, cut off the pressure-receiving device and dispose of it.
Professional instruments such as oxygen meters must be strictly prohibited. The method of inspection will inject pure warm water into the spring tube, and after shaking, and then the water will be immersed in the utensils with clear water, there is no colored oil shadow on the water surface, then it can be considered that there is no grease. Oxygen meters with grease were found to be rinsed with boiling water or with carbon tetrachloride. In addition, professional instruments are strictly prohibited for other uses.
Check the timing to check the integrity of the instrument. Keep the instrument clean, especially check the indication value of the pressure gauge, and carry out the pressure test on the equipment and pipeline during production. The test pressure is a multiple of the working pressure. Pressure measuring instruments equipped with venting, exhausting and dust removal devices should be regularly vented, drained and dedusted.
The pressure measuring instrument installed at the outlet of the pump, in order to prevent the instrument from being damaged by the instantaneous impact and overpressure, when starting the pump, the valve in front of the pressure gauge should be closed first, and then the valve should be slowly opened after the pump starts, which is often started. The pump is very important and should be noted. The pressure gauges to be operated must be regularly verified. The inspection cycle is generally six months according to the procedure. However, the pressure gauges with high frequency in the work can shorten the verification cycle appropriately.
The above is not necessarily complete and should be handled according to the specific conditions to ensure the normal operation of the instrument and reduce and eliminate the fault. Improve the meter integrity and extend the life of the meter.
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