How to test the solid content of additives?

Solid content (solids content) is a commonly used indicator for testing liquid additives. It generally reflects the effective content of the additive and can be used as a reference for comparing multiple additives or for batch comparison testing. However, solid content does not represent the effective content of the additive.

I. Oven Method

1. Principle

A certain mass of sample is dried at a certain temperature and pressure for a certain time. The solid content is expressed as the percentage of the sample mass after heating to the sample mass before heating.

2. Determination Steps

① Take three weighing bottles and dry them in an oven at (105±2)°C for 1.5 hours. After cooling in a desiccator for 30 minutes, weigh them and record them as m1. ② Weigh 1-2g (accurate to 0.0001g) of the sample into the dried weighing bottle and record them as m. ③ Gently transfer the sample to the weighing bottle so that the sample is evenly distributed on the bottom of the weighing bottle. Slightly open the lid of the weighing bottle and place it in an oven at (105±2) ℃. Turn on the blower and dry for 3 hours. Then cover the bottle tightly and place it in a desiccator to cool for 30 minutes. Weigh it and record it as m2. 

3. Calculation of results

 The solid content of the sample is expressed as mass fraction X. The value is expressed in (%) and is calculated according to formula (1): X=(m2-m1)/m×100% (1) Where: m——the value of the sample mass. Unit is gram (g); m1——the value of the sample mass. Unit is gram (g); m2——the value of the mass of the weighing bottle and the sample after drying. Unit is gram (g). Take the arithmetic mean of the two parallel determinations and round it to 0.1% according to GB/T8170-2008 to obtain the determination result. The difference between the two parallel determination results shall not exceed 0.3%.

2. Sugar Meter Method

1.Principle

The sugar content of a solution, measured using the principle of refraction, is proportional to its solid content. By measuring the sugar content of the solution and using a specific proportionality factor, the solid content of the sample can be calculated.

2. Measurement Procedure

The test should be performed at room temperature. The sample must be equilibrated to room temperature before measurement.

① Clean the surface of the sugar meter prism. Add approximately 0.3 mL of water to the surface. Adjust the zero value according to the sugar meter's operating instructions.

② Discard the water from the sugar meter, wipe the prism dry, and add approximately 0.3 mL of sample to the surface. Measure the sugar content of the sample according to the sugar meter's operating instructions until the readings remain stable. This is recorded as the sugar content of the sample, A.

③ Calculate the solid content of the sample using the proportionality factor n between the solid content and sugar content, obtained from the accumulated data.

Note: Because this method uses the principle of refraction, do not use it for samples that are difficult to clean with water. Doing so may contaminate the prism surface and result in inaccurate results. 3. Calculation of Results

The solid content of the sample is expressed as mass fraction X, and the value is expressed in (%). It is calculated according to formula

(2): X = n×A

(2) Where: n is the conversion coefficient between solid content and sugar content; A is the sugar content of the sample, %