Dimethyl malonate for industrial use (3)

4.

4.

Using phenolphthalein as an indicator, titrate the free acid content in the sample with a standard sodium hydroxide titration solution

4.

4.

4.

4.

4.

Weigh about 5g of the sample (accurate to 0.

4.

The content X ₂ of acid ( calculated as C ₃ H ₄ O ₄ ) expressed in mass percentage is calculated according to formula (2):

In the formula: V— the volume of the sodium hydroxide standard titration solution consumed by the titration sample , mL;

c ₂ —The actual concentration of sodium hydroxide standard titration solution, mol/L;

m2—the mass of the sample, g;

0.

Take the arithmetic mean of the two parallel determination results as the determination result

4.

Weigh about 2g of the sample (accurate to 0.

Take the arithmetic mean of the two parallel determination results as the determination result

5 Inspection rules

5.
1 All items specified in this standard are ex-factory inspection items
.

5.
2 Dimethyl malonate for industrial use should be inspected by the quality inspection department of the manufacturer
.
The manufacturer shall ensure that all manufactured products meet the requirements of this standard
.

Each batch of products that leave the factory should be accompanied by a quality certificate in a certain format, the content of which includes the product name, product grade, manufacturer name, factory address, batch number or production date and the number of this standard
.

5.
3 Dimethyl malonate for industrial use is based on the one-time canning quantity of one production unit as one batch
.

5.
4 The number of sampling units shall be determined in accordance with 6.
6 of GB/T6678-1986
.
The sampling technique should meet the requirements of GB/T6680
.
When sampling, the insertion depth of the sampling glass tube is not less than 3/4 of the barrel to ensure that the sample taken is representative of the upper, middle, and lower layers
.
The total sample volume is not less than 0.
5L, and the mixture is evenly mixed and then packed into two clean and dry 250mL glass bottles with a ground mouth
.
Affix the label and indicate the product name, product grade, batch number, sampling date and the name of the sampler
.
One bottle is for inspection, the other is sealed and kept for two months for future reference
.

5.
5 The test result is judged according to the rounding value comparison method in GB/T1250
.
If one of the inspection results does not meet the requirements of this standard, samples shall be taken from twice the number of packaging units for re-inspection
.
Even if only one index does not meet the requirements of this standard as a result of the re-inspection, the whole batch of products is unqualified
.

6 Marking, packaging, transportation and storage

6.
1 The packaging container of dimethyl malonate for industrial use should have a firm and clear mark, which includes the product name, trademark, manufacturer name, site, net content, batch number, number of this standard and the "upward" mark specified in GB191
.

6.
2 Dimethyl malonate for industrial use should be put into clean, dry plastic drums with inner lids or plastic drums
.
The net weight per barrel is 200kg
.
Or according to the contract requirements of the supplier and the buyer
.

6.
3 When transporting dimethyl malonate for industrial use, handle it with care, no knocks, and no upside-down
.

6.
4 Dimethyl malonate for industrial use should be stored in a cool, dry, ventilated and fireproof warehouse
.

Related links: Dimethyl malonate for industrial use (2)