One, oven method
1, the principle of
: the sample with a certain mass is dried at constant pressure for a certain time at a certain temperature. The percentage of the sample mass after heating and the sample mass before heating represents the solid content.
2. Determine step polymerization
(1) take three weighing bottles, dry in the oven at (105±2) ℃ for 1.5h, cool in the dryer for 30min before weighing, denoting as m1.
(2) the sample of 1 ~ 2g (accurate to 0.0001g) was placed in a dry weighing flask, denoted as m.
(3) gently turn to the weighing bottle, so that the sample is evenly distributed at the bottom of the weighing bottle. The cap of the weighing bottle is slightly opened and placed in the oven at (105±2) ℃. After the blower is turned on and dried for 3h, the bottle cap is tightly covered and cooled in the dryer for 30min.
3. Calculation of results
The solid content of the sample is measured by mass fraction X, and the value is expressed by (%), calculated according to equation (1) :
X= (m2-m1)/m×100% (1)
M -- the value of sample mass. The unit is gram (g);
M1 -- value of sample mass. The unit is gram (g);
M2 -- the value of the mass of the measuring bottle and sample after drying. It's in grams.
The arithmetic mean value of the two parallel measurements was taken and adjusted to 0.1% according to GB/ t8170-2008. The difference between the two parallel measurements was no more than 0.3%.
Second, the saccharometer method
By using the principle of refraction, the sugar content of the solution is proportional to its solid content.
2. Determination steps:
The test should be carried out at room temperature, and the sample should be balanced to room temperature before determination.
(1) clean the surface of the saccharometer prism, drop about 0.3mL of water on the surface, according to the saccharometer operating instructions zero.
(2) discard the water from the saccharometer, dry the prism, drop about 0.3mL of the sample on its surface, and determine the saccharinity of the sample according to the operation manual of the saccharinity meter. The saccharinity of the sample remains unchanged after reading twice and is recorded as sample saccharinity A.
(3) according to the proportional coefficient n between solid content and sugar content obtained by data accumulation, the solid content of the sample was converted.
Note: since this method is tested by refraction principle, do not use it in the test of samples that are difficult to wash, otherwise it will contaminate the surface of the prism and the test is not accurate.
3. Calculation of results
The solid content of the sample is measured by mass fraction X, and the value is expressed by (%), calculated according to equation (2) :
X = n * A ----- (2).
N -- conversion coefficient of solids content and sugar content
A -- sugar degree of sample, %