Scope and Application Standards of Food Additives: magnesium silicate 
(synthetic)  
 
17. Others: 
Code Food 
Additive 
Items Scope and Application 
Standards Limitations 
017 Magnesium 
silicate 
(synthetic) Fats and oils filtering: 
not more than 0.2 %. For filtering aid and anticaking agent purpose. 
 Specification Standards of Food Addi tives: magnesium silicate (synthetic)  
 
§ 17017 Magnesium Silicate (Synthetic) 
1. Synonyms: INS No. 553(i) 
2. Definition: Magnesium silicate (synthetic) is manufactured by the 
precipitation reaction between sodium silicate and a soluble 
magnesium salt. The a queous suspension of the precipitate is 
filtered and the collected solid washed, dried, classified for 
particle size and packaged. The fi nest material is intended for use 
as an anticaking agent and the co arser particles are for use as a 
filtering aid. Although magnesium  silicate is of variable 
composition, the molar ratio of MgO to SiO2 is approximately 2:5. 
3. Characters: Very fine, white , odourless powder, free from grittiness 
4. Content: Not less than 15% of MgO and not less than 67% of SiO2, calculated 
on the ignited basis.  
5. Identification: 
(1) Solubility: Insoluble in water and in ethanol; readily decomposed by 
mineral acids. 
(2) pH: 7.0-10.8 (1 in 10 slurry)  
(3) Magnesium: Mix about 0.5 g of th e sample with 10 ml of 2.7N 
hydrochloric acid TS, filter, and neutra lize the filtrate to litmus paper with 
6N ammonia TS. The neutralized filtrate gives a positive test for 
magnesium. 
(4) Silicate: Prepare a bead by fusing a few crystals of sodium ammonium 
phosphate on a platinum loop in the fl ame of a Bunsen burner. Place the 
hot, transparent bead in contact with  the sample, and again fuse. Silica 
floats about in the bead, producing, upon cooling, an opaque bead with a 
web-like structure.  
6. Loss on drying: Not more than 15% (105°, 2 h) 7. Loss on ignition: Not more than 15% on the dried basis. Weigh to the nearest 
0.1 mg, 1 g of the dried sample in a tared platinum crucible provided with a cover. Gradually  apply heat to the crucible 
at first, then strongly ignite at 900/1000° for 20 min. Cool, weigh and calculate as percentage. 
8. Soluble salts: Not more than 3%. Bo il 10 g of the sample with 150 ml of 
water for 15 min. Cool to room temperature, and add water to 
restore the original volume. Al low the mixture to stand for 15 
min, and filter until clear. Retain 20 ml of the filtrate for the test Free alkali. Evaporate 75 ml of th e filtrate, representing 5 g of 
the sample in a tared platinum dish on a steam bath to dryness, 
and ignite gently to constant weight. Cool, weigh and calculate as percentage (the weight of the residue should not exceed 150 
mg). 8.Sodium chloride: Not mo re than 0.5 % on dried basis. 
9. Free alkali: Not more than 1% (as Na OH). Add 2 drops of phenolphthalein TS 
to 20 ml of dilute filtrate prepared  in the test for Soluble salts (see 
below), representing 1 g of the sa mple. Not more than 2.5 ml of 
0.1 N hydrochloric acid should be required to discharge the pink colour produced.
  
10. Fluoride: Not more than 10 mg/kg (Fluoride Limit Test). 11. Lead: Not more than 5 mg/ kg (Atomic absorption technique). 
12. Category: Food additives category (17) 13. Functional uses: Filtering aid and anticaking agent.