Page:NIOSH Manual of Analytical Methods - 1614.pdf/6

 ETHYLENE OXIDE: METHOD 1614, Issue 2, dated 15 August 1994 - Page 6 of 6

APPENDIX D: STANDARDIZATION OF ETHYLENE OXIDE STOCK SOLUTION [7] 1. 2. 3.

4. 5. 6. 7.

Pipet 20.0 mL standardized HCl-pyridine solution into a 100-mL round bottom flask. Add 2.0 mL EtO stock solution. Attach the flask to the condenser. Reflux for 20 min. NOTE: The reaction is: EtO + HCl(xs) chloroethanol. The excess HCl is back-titrated in step D-6. Cool to near room temperature. Add 5 mL distilled H 2O through the condenser, collecting washings in the flask. Remove the condenser and add a drop of phenolphthalein solution to the flask. Titrate, with mixing, 0.5 N NaOH from the burette to a pink endpoint. Record volume,c V(mL), of NaOH used. Calculate the normality, Ns, of the excess HCl using Nb from APPENDIX B:

Ns

8. 9.

NbVc 20 mL

.

Repeat steps 1 through 7 to obtain an average of two titrations. Results should agree to within 1%. Rinse flask thoroughly before reuse. Calculate the concentration of the EtO stock solution: mg EtO mL EtO stock solution

(No

Ns)

20 mL 103 mL

44.05 g 1 equivalent

1 2 mL

103 mg 1 g

(No

NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94

Ns)

440.5