Packaging and storage
Preserve in tight containers.
Identification
It responds to the tests for Zinc á191ñand for Sulfate á191ñ.
pHá791ñ:
between 5.8and 6.2;or,if it contains sodium citrate,between 7.2and 7.8.
Assay
Pipet into a beaker a volume of Ophthalmic Solution,equivalent to about 25mg of zinc sulfate.Add 1mLof glacial acetic acid,and adjust by the dropwise addition of 6Nammonium hydroxide to a pHof between 5.0and 5.5.Add 1drop of copper ethylenediaminetetraacetate solution [prepared by mixing 1mLof cupric sulfate solution (1in 40)and 1mLof 0.1Medetate disodium]and 3drops of a 1in 1000solution of 1-(2-pyridylazo)-2-naphthol in anhydrous methanol,and titrate with 0.01Medetate disodium VS.Each mLof 0.01Medetate disodium is equivalent to 1.614mg of ZnSO4.