USGS-NWQL: I-1749: Solids, residue at 105 degrees C, dissolved, gravimetric

Summary
Analytes
Revision
Data and Sites

Official Method Name

Solids, residue on evaporation at 105 degrees C, dissolved, gravimetric

Current Revision

1975

Media

WATER

Instrumentation

Gravimetry

Method Subcategory

Inorganic

Method Source

USGS-NWQL

Citation

Methods for the Determination of Inorganic Substances in Water and Fluvial Sediments, Techniques of Water-Resources Investigations of the United States Geological Survey, Book 5, Chapter A1 Edited by Marvin J. Fishman and Linda C. Friedman

Brief Method Summary

A volume of filtered sample that will yield less than 200 mg residue is evaporated just to dryness on a steam bath. The residue is dried at 105^oC for 2.0 h, cooled in a desiccator, and immediately weighed.
The weight of the residue is limited to 200 mg to ensure subjection of all the residue to the full effects of drying at 105^oC. Voluminous residues will often seal over during the evaporation process and entrap pockets of water that will not be completely vaporized during the drying process. Massive residues also release their water of crystallization more slowly than do thin films of residue. The chemical composition of the sample has a marked effect on the dissolved-solids value obtained, but the percentage of error incurred for any given chemical type of water is independent of the total concentration if the residue film is kept thin.
Because many of the salts in the residue are hygroscopic, an efficient desiccant must be used. Silica gel (indicating), anyhydrous Mg(ClO₄)₂ or CaSO₄, and Mg(ClO₄)₂ multiplied by 3H₂O are satisfactory and recommended. CaCl₂ is not suitable. Under no circumstances should the dried residues be allowed to stand for long periods of time before weighing.

Scope and Application

The residue-on-evaporation method is applicable to all water regardless of concentration, provided that the residue layer in the evaporating dish is kept sufficiently thin.

Applicable Concentration Range

Not over 200 mg of residue for analysis. Samples may be diluted to achieve less than 200 mg residue.

Interferences

There are no known interferences to this method.

Quality Control Requirements

Laboratory blanks (LB)

Sample Handling

Container Description: 250 or 500 mL polyethylene bottle.
Handling and Treatment: Filter through 0.45 micron filter; use filtered sample to rinse container.

Maximum Holding Time

Relative Cost

Less than $50

Sample Preparation Methods

This method has 1 analyte associated with it.

Analyte	Detection Level	Bias	Precision	Pct False Positive	Pct False Negative	Spiking Level
Total Dissolved Solids(E-10173) Residue, Filterable TDS Total Dissolved Solids	1.000 mg/L	N/A	N/A

Precision Descriptor Notes:	It is estimated that the percent relative standard deviation of this method is greater than 8 percent at 59 mg/L and greater than 3 percent at 1760 mg/L.
Detection Level Note:	Reporting Level defined as smallest measured concentration of a constituent that may be reliably reported using a given analytical method.

Revision	PDF/Link
1975

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USGS-NWQL: I-1749: Solids, residue at 105 degrees C, dissolved, gravimetric

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