Abstract Method for determining the sulfate ion concentration of an aqueous solution. The mechanism of the method resides in the use of a chelate of a metal which under acidic conditions dissociates to release metal ions which will react with the sulfate ion present to produce a colloidal metal sulfate precipitate. In order to ensure that the free chelant does not precipitate or react to form a precipitate, there is also added to the solution a quantity of a metal compound, the metal of which will replace the original metal of the chelate to form a water soluble second chelate. The turbidity or color density of the aqueous solution is measured and compared to the color density values obtained for solutions containing known quantities of sulfate precipitate of the same metal.
A method according to claim 1 wherein a materIal capable of stabilizing the precipitate formed upon adjustment of the solution to an acid pH is added to said solution.
Claim 2
Dependent Claim
27 words
A method according to claim 1 wherein said metal chelate compound is a barium-ethylenediaminetetraacetic acid chelate and said water-soluble compound of said second metal is aluminum chloride.
Claim 3
Dependent Claim
30 words
A method according to claim 3 wherein the pH of said solution is adjusted to a pH of from about 2.5 to about 5.5 by the addition of hydrochloric acid.
Claim 4
Dependent Claim
29 words
A method according to claim 4 wherein a material capable of stabilizing the precipitate formed upon adjustment of the solution to an acidic pH is added to said solution.
Claim 5
Dependent Claim
22 words
A method according to claim 5 wherein said pH is adjusted by adding a solution containing hydrochloric acid, sodium chloride and glycerine.
Claim 6
Dependent Claim
28 words
A method according to claim 3 wherein said aqueous solution containing said sulfate is filtered prior to the addition of said chelate compound and said second metal compound.
Claim 7
Dependent Claim
53 words
A method according to claim 1 wherein the metal chelate compound is selected from the group consisting of barium-ethylenediaminetetraacetic acid chelate, barium-nitrilotriacetic acid chelate and barium-diethylene-triamine pentaacetic acid chelate, and said water-soluble compound of a second metal is selected from the group consisting of copper chloride, ferric chloride, chromous chloride and zinc chloride.