Sulfatos

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version of the standard as published by ASTMis to be considered the official document.

Designation:D 3875–03 Designation: D 3875 – 08

Standard Test Method for

Alkalinity in Brackish Water, Seawater, and Brines1
This standard is issued under the fixed designation D 3875; the number immediately following the designation indicates the year of original adoption or, in the case of revision, the year of last revision. A number inparentheses indicates the year of last reapproval. A superscript epsilon (´) indicates an editorial change since the last revision or reapproval.

1. Scope * 1.1 This test method covers the determination of alkalinity in brackish water, seawater, and brines. 1.2 1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.3 Thisstandard does not purport to address all of the safety concerns, if any, associated with its use. 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. 2. Referenced Documents 2.1 ASTM Standards: D 1129 Terminology Relating to Water D 1193Specification for Reagent Water2Specification for Reagent Water D 2777 Practice for Determination of Precision and Bias of Applicable Test Methods of Committee D19 on Water D 3370 Practices for Sampling Water from Closed Conduits D 5847 Practice for Writing Quality Control Specifications for Standard Test Methods for Water Analysis E 200 Practice for Preparation, Standardization, and Storage of Standard and Reagent Solutions for ChemicalAnalysis 3. Terminology 3.1 Definitions—ForFor definitions of terms used in this test method, refer to Terminology D 1129. 4. Summary of Test Method 4.1 An electrotitrator or pH meter is used to determine the amount of acid necessary to reach pH 8.1 and 4.5, respectively. The pH values approximate the points where the hydroxide and bicarbonate ions are neutralized. 5. Significance and Use 5.1 Alkalinityas carbonate and bicarbonate of saline water is very important in chemical waterflooding or tertiary recovery processes for recovering petroleum. Alkaline waters offer better wetting to the formation rock and improve oil release. As an additional benefit, ions that provide alkalinity adsorb on rock surfaces occupying adsorption sites and decrease the loss of recovery chemical by adsorption.Determination of alkalinity in waters used in tertiary recovery processes is therefore very important. 5.2 An alkalinity value is necessary in the calculation of carbonate scaling tendencies of saline waters. It is also necessary to determine the alkalinity if the ionic balance of a water analysis is to be used as a check of the reliability of the analysis. 6. Interferences 6.1 Anions other thanbicarbonate, carbonate, or hydroxide ions that form weakly dissociated acids that participate in hydrolysis reactions may also contribute to the alkalinity as may some organic materials. The user of this test method on determining the alkalinity is cautioned that all the effects of the anions entering into hydrolysis reactions are combined and reported as an equivalent amount of a single substance or twopostulated ions. Included in the reported value is the alkalinity resulting from the presence of borate, silicate, sulfide, and phosphate. The effect of borate on the alkalinity value is considered negligible for waters with pH values of 7 or less. 7. Apparatus 7.1 Electrotitrator or Standard pH Meter with suitable electrodes. Maintenance and standardization of electrodes and pH meter
1 This...