Colloidal Silicon Dioxide
SiO2
60.08
Silica.
Silica [7631-86-9].
»Colloidal Silicon Dioxide is a submicroscopic fumed silica prepared by the vapor-phase hydrolysis of a silicon compound.When ignited at 1000
for 2hours,it contains not less than 99.0percent and not more than 100.5percent of SiO2.
for 2hours,it contains not less than 99.0percent and not more than 100.5percent of SiO2.
Packaging and storage—
Preserve in well-closed containers.
Identification—
A:
Transfer about 5mg to a platinum crucible,and mix with about 200mg of anhydrous potassium carbonate.Ignite at a red heat over a burner for about 10minutes,and cool.Dissolve the melt in 2mLof freshly distilled water,warming if necessary,and slowly add 2mLof ammonium molybdate TSto the solution:a deep yellow color is produced.
B:
[Caution—Avoid contact with o-tolidine when performing this test,and conduct the test in a well-ventilated hood.
]Place 1drop of the yellow silicomolybdate solution obtained in Identificationtest Aon a filter paper,and evaporate the solvent.Add 1drop of a saturated solution of o-tolidine in glacial acetic acid to reduce the silicomolybdate to molybdenum blue,and place the paper over ammonium hydroxide:a greenish blue spot is produced.
pHá791ñ:
between 3.5and 5.5,in a 1in 25dispersion.
Loss on drying á731ñ—
Dry it in a tared platinum crucible at 105for 2hours:it loses not more than 2.5%of its weight.Retain the dried specimen,in the crucible,for the test for Loss on ignition.
for 2hours:it loses not more than 2.5%of its weight.Retain the dried specimen,in the crucible,for the test for Loss on ignition.
Loss on ignition á733ñ—
Ignite the portion of Colloidal Silicon Dioxide,retained from the test for Loss on drying,at 1000±25to constant weight:the previously dried Colloidal Silicon Dioxide loses not more than 2.0%of its weight.
to constant weight:the previously dried Colloidal Silicon Dioxide loses not more than 2.0%of its weight.
Arsenic,Method Iá211ñ—
Prepare the Test Preparationas follows.Transfer 2.5g to a flask,add 50mLof 3Nhydrochloric acid,and reflux for 30minutes using a water condenser.Cool,filter with the aid of suction,and transfer the filtrate to a 100-mLvolumetric flask.Wash the filter and flask with several portions of hot water,and add the washings to the flask.Cool,dilute with water to volume,and mix:a 15.0-mLportion of this solution,to which 3mLof hydrochloric acid has been added,meets the requirements of the test,the addition of the 7Nsulfuric acid being omitted.The limit is 8µg per g.
Organic volatile impurities,Method IVá467ñ:
meets the requirements.
Assay—
Transfer about 500mg of Colloidal Silicon Dioxide to a tared platinum crucible,ignite at 1000±25for 2hours,cool in a desiccator,and weigh.Add 3drops of sulfuric acid,and add enough alcohol to just moisten the sample completely.Add 15mLof hydrofluoric acid,and in a well-ventilated hood evaporate on a hot plate to dryness,using medium heat (95to 105)and taking care that the sample does not spatter as dryness is approached.Heat the crucible to a red color with the aid of a Bunsen burner.Ignite the residue at 1000±25for 30minutes,cool in a desiccator,and weigh.If a residue remains,repeat the procedure,beginning with “add 15mLof hydrofluoric acid.”The weight lost by the assay specimen,previously ignited at 1000±25,represents the weight of SiO2in the portion taken.
for 2hours,cool in a desiccator,and weigh.Add 3drops of sulfuric acid,and add enough alcohol to just moisten the sample completely.Add 15mLof hydrofluoric acid,and in a well-ventilated hood evaporate on a hot plate to dryness,using medium heat (95to 105)and taking care that the sample does not spatter as dryness is approached.Heat the crucible to a red color with the aid of a Bunsen burner.Ignite the residue at 1000±25for 30minutes,cool in a desiccator,and weigh.If a residue remains,repeat the procedure,beginning with “add 15mLof hydrofluoric acid.”The weight lost by the assay specimen,previously ignited at 1000±25,represents the weight of SiO2in the portion taken.
Auxiliary Information—
Staff Liaison:Justin Lane,B.S.,Scientific Associate
Expert Committee:(EMC)Excipients:Monograph Content
USP28–NF23Page 3074
Phone Number:1-301-816-8323