This method is included in NEMI for informational purposes as it is approved by EPA for regulatory use. Detailed information on this method is not currently. eropoly acid. This is reduced to silicomolybdenum blue that is determined pho- tometrically. The method is analogous to APHA SiO2 D+E, ASTM D, . Find the most up-to-date version of ASTM D at Engineering
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Under the allowances made in 1. The lower limit of this method is 5 mg of silica.
Standard Test Method for Silica in Water
No other units of measurement are included in this standard. Last previous edition approved in as D — Silica may exist in suspended particles, as a colloid, or in solution.
Active view current version of standard Translated Standard: The upper limit for acceptable precision and the range of acceptable recoveries are detailed below: A superscript epsilon e indicates an editorial change since the last revision or reapproval.
Historical Version s – view previous versions of standard Translated Version s: Link to Active This link will always route to the current Asgm version of the standard.
Since the method includes an evaporation step, the applicable concentration range depends upon the volume of sample used in the determination. High blanks, nonlinear calibration curves, and poor reproducibility have been observed with some batches of this compound.
This is acceptable when, as frequently occurs, the molybdate-reactive silica is in the milligram per litre concentration range while the nonmolybdate-reactive silica, if present at all, is in the microgram per litre concentration range. Prepare a blank using a Make up to mL with water and store in a dark, s859 bottle.
Check the concentration of this solution gravimetrically.
If the value still falls outside acceptable limits, a new calibration curve is required that must be con? In solution it can exist as silicic acid or silicate ion, depending upon pH. The values obtained must fall within the limits speci? NOTE 4—Batch to batch variations in ammonium molybdate have been found to affect results at low concentrations below 0.
If non-detects are expected in all the samples to be analyzed, a Matrix Spike Duplicate should be run instead. Due to the complexity of silica chemistry, the form of silica measured is de? Due to the complexity of silica chemistry, the form of silica measured is defined aetm the analytical method as molybdate-reactive silica.
ASTM D – 10 Standard Test Method for Silica in Water
For seawater or brines, this test method is applicable only if matched matrix standards or standard addition techniques are employed. The CVS is a solution of the method analyte of known concentration mid-calibration range used to fortify reagent water. Silicon is the most abundant element in igneous rocks and is the characteristic element of all important rocks except the carbonates.
The presence of most silica in natural waters comes from the gradual degradation of silica-containing minerals. Analyte Silica MS Amount ?
ASTM D859 – 16
For seawater or brines, this test method is applicable only if matched matrix standards or standard addition techniques are employed. Silica removal is commonly accomplished by ion exchange, distillation, reverse osmosis, or by precipitation, usually with magnesium compounds in a hot or cold lime softening process. In addition, the water shall be made silica-free by distillation or demineralization and determined as such in accordance with the method of test being used.
When working with low concentrations of silica, a batch of ammonium molybdate known to produce reasonable blanks, linearity, and reproducibility should be set aside for this purpose. Dehydration is completed by ignition, and the silica is volatilized as silicon tetra?
Spectrophotometers shall conform to Practice E Those forms of silica that are molybdate-reactive include dissolved simple silicates, monomeric silica and silicic acid, and an undetermined fraction of polymeric silica. The level 2 spiking solution used for the precision and bias study is a suitable IDP solution. Your comments are invited either for revision of this standard or for additional standards and should be addressed to ASTM International Headquarters.
Reagents and Materials NOTE 3—Store all reagents to be used in this test method in polyethylene or other suitable plastic bottles. A direct reading spectrophotometer or? Your comments will receive careful consideration at a meeting of the responsible technical committee, which you may attend.
It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
Precision and Bias 5 It is particularly applicable to treated industrial waters. It may be monomeric or polymeric. Refer to Appendix X1 for historical information. This is acceptable when, as frequently occurs, the molybdate-reactive silica is in the milligram per litre concentration range while the nonmolybdate-reactive silica, if present at all, is in the microgram per litre concentration range.
For many natural waters, a measurement of molybdate-reactive silica by this test method provides a close approximation of total silica, and, in practice, the colorimetric method is frequently substituted for other more time-consuming techniques.