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Titration for Determining Active Chelate (EDTA) Remaining in Soldering Flux

IP.com Disclosure Number: IPCOM000049400D
Original Publication Date: 1982-Apr-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Bayer, S: AUTHOR

Abstract

The percent of active EDTA remaining in an EDTA/glycerine soldering flux is found by titrating a flux sample with copper nitrate. At the end point of the titration, the original percent of active chelate equals 148.9 (molarity of copper nitrate) (volume of copper nitrate/ solution)/ (sample weight). The volume of copper nitrate is in milliliters, the molarity of copper nitrate is in moles per liter, and the sample weight is in grams.

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Titration for Determining Active Chelate (EDTA) Remaining in Soldering Flux

The percent of active EDTA remaining in an EDTA/glycerine soldering flux is found by titrating a flux sample with copper nitrate. At the end point of the titration, the original percent of active chelate equals 148.9 (molarity of copper nitrate) (volume of copper nitrate/ solution)/ (sample weight). The volume of copper nitrate is in milliliters, the molarity of copper nitrate is in moles per liter, and the sample weight is in grams.

A flux of ethylenediamine tetraacetate (EDTA) end glycerine is conventionally maintained over a liquid solder bath to remove oxides on the surface of copper that is to be soldered and the surface of the tin component of the solder. It is desirable to test samples of the flux to determine whether a sufficient percent of the active chelate remains.

A measured amount of about 3 to 5 grams of an EDTA/glycerine sample is transferred to a 100 ml flask and a 25 ml aliquot of this solution is pipetted into a 250 ml beaker containing 10 ml of a pH 5.5 sodium acetate/ acetic acid buffer. This sample is titrated with a standardized solution of copper nitrate, and the potential is measured between a copper ion selective electrode and a calomel reference electrode and a plot of voltage versus volume of copper nitrate solution is made. So long as active EDTA remains, it binds to the copper ions and thereby prevents the conductivity of the solution from rising. After the nu...