This standard specifies the vacuum oven method for determining the free water content in compound fertilizers. This standard is not applicable to compound fertilizers that can produce non-water volatile substances during the drying process. GB/T 8576-2002 Determination of free water content in compound fertilizers Vacuum oven method GB/T8576-2002 Standard download decompression password: www.bzxz.net

1 Scope
Determination of free water content in compound fertilizersbzxz.net
Vacuum oven method
This standard specifies the determination of free water content in compound fertilizers by vacuum oven method. This standard is not applicable to compound fertilizers that can produce non-water volatile substances during the drying process. 2 Normative references
GB/T8576-2002
The clauses in the following documents become the clauses of this standard through reference in this standard. For all dated references, all subsequent amendments (excluding errors) or revisions are not applicable to this standard. However, parties to an agreement based on this standard are encouraged to study whether the latest versions of these documents can be used. For any undated referenced document, its latest version shall apply to this standard. GB/T8571 Compound fertilizer
3.1 General laboratory instruments:
Preparation of laboratory samples
3-2 Electric constant temperature vacuum oven (the temperature of the vacuum oven can be controlled at 50°C ± 2°C, and the vacuum degree can be controlled at 6.4×10P~7.1X10Pa:
3.3 Weighing bottle with ground stopper: 50mm in diameter and 30mm in height. 4 Steps
Prepare laboratory samples according to GB/T8571. Weigh 2g of laboratory sample in a weighing bottle that has been dried and weighed in advance. . Weigh to 0.0001g and place it at 50℃±2℃, pass dry air and adjust the vacuum degree to 6-4×1oPa~7.1×10Pa in an electric constant temperature vacuum drying oven and dry it for 2h±10min. Take it out, cool it to room temperature in the dryer, and weigh it.
5 Calculation and expression of analysis results
5.1 Calculation of analysis results
The free water content is expressed as mass fraction W (free water) %) and calculated according to formula (1): W (free water)
Where:
The mass of the sample before drying, in grams (g): The mass of the sample after drying, in grams (g). Take the arithmetic mean of the parallel determination results as the determination result 5.2 Allowable error
When the mass fraction of free water W (free water) is ≤2.0%, the absolute difference of the parallel determination results should be ≤0.20%; when the mass fraction of free water W (free water) is >2.0%, the absolute difference of the parallel determination results should be <0.30%.
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