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Oregon State University

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Oregon State University was founded more than 150 years ago as a land grant institution, building on the idea that everybody deserves an extraordinary education that’s attainable and accessible. Here you can determine your purpose, shape your identity and values and become who you want to be.

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Oregon State’s beautiful, historic and state-of-the-art campus is located in one of America’s best college towns. Nestled in the heart of the Willamette Valley, Corvallis offers miles of mountain biking and hiking trails, a river perfect for boating or kayaking and an eclectic downtown featuring local cuisine, popular events and performances.

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Oregon State’s Bend campus, located in the stunning high desert of Central Oregon, offers more than 20 majors, small classes and a vast natural laboratory. Nearby, endless outdoor recreation options await — including skiing, snowshoeing, rock climbing, paddle boarding and more.

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Oregon State Ecampus blends 21st century innovation with 150+ years of institutional excellence to give people everywhere access to a life-changing education online. Everything we do is designed to help Oregon State students:

  • Make an impact in their communities and beyond
  • Feel supported along every step of their journey
  • Build connections with OSU’s world-class faculty
  • Enter the workforce with the skills they need to succeed
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With operations in all 36 counties and the Confederated Tribes of Warm Springs, Oregon State University is a trusted partner serving Oregonians statewide. The OSU Extension Service delivers research-based knowledge and education that strengthen communities and economies, sustain natural resources and promote healthy people and families. The 11 Agricultural Experiment Stations at 14 locations address critical issues across landscapes, oceans and food systems. The Forest Research Laboratory manages 10 research forests and develops innovative approaches for managing forest resources and ecosystems.

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At Oregon State’s coastal research center in Newport, you can dip your toes in the Pacific Ocean — and pursue hands-on, experiential learning through classes, research and internships aimed at developing solutions to pressing environmental issues.

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The OSU Portland Center is a premier event, meeting and conference venue for showcasing Oregon State programs, initiatives, research and exhibitions. OSU also offers a hybrid MBA and pharmacy programs, professional development courses and a variety of Extension programs in Portland.

Oregon's best public research university

With nearly 200 degree programs Oregon State has a path to the career and future you always wanted. 

As Oregon’s largest university, we draw people from all 50 states and more than 100 countries to a welcoming community that supports success, well-being and belonging for all. We are constantly learning, innovating and applying new skills to make the world better. You can too.

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Home > Method

Method



    Determination of formaldehyde concentration by Iodine titration

    This protocol is based on the following reactions:
    • CH2O + I2 → CH2O2 + 2 I- + I2 (excess)
    • I2(excess) + 2 S2O32- → 2 I- + S4O62-
    By titrating excess I2 with a known quantity of S, the original number of moles of formaldehyde (CH2O) can be back calculated. The only solutions that need to be measured very precisely are the diluted formaldehyde solution and the 0.1 M sodium thiosulfate solution.

    Solutions:

    Prepare the following reagents in advance:
    • Iodine solution (0.05 M or equivalently 0.1 N): weigh 0.6305 g of I2 and 1.5 g of KI (KI is necessary to dissolve the I2. If the I2 does not dissolve completely, add more KI). Dilute to 50 mL with H2O.
    • Starch indicator solution: Suspend 1 g of starch into 200 mL H20 (supermarket corn starch will work just fine). Bring to boil for 5 minutes (not all starch will dissolve). Add 6 mL concentrated HCl and dilute to 500 mL with H2O. Let sediment, pour off supernatant.
    • Sodium thiosulfate (0.1 M; use a volumetric flask fo accuracy): weigh 2.4 g Na2S2O3·5 H2O and dissolve to 100 mL with H2O.
    • Sodium hydroxide (1 M): weigh 2 g of NaOH pellets, dilute to 50 mL with H2O.
    • Sulfuric acid (25%): add 12.5 ml H2SO4 to ~ 30 mL H2O, dilute to 50 mL with H2O.
    • Diluted formaldehyde solution: 0.625 mL of original commercial stock (~37% w/v) diluted to 250 mL with H2O (use a volumetric flask).


    Now you are ready to do the experiment

    To two 20 mL beakers with a stir bar add in the following order:
    • 4 mL of diluted formaldehyde solution in one beaker, 4 mL of H2O in the other beaker as the control.
    • 5 mL of Iodine solution into both.
    • 2 mL 1 M NaOH into both. (Solution will turn light yellow from a dark brown; WAIT 15 MINUTES).
    • Add sulfuric acid into both beakers until solution is dark brown again (~2-3 mL).
    • Add starch indicator solution to both beakers, 1 mL.

    With a burete, pipette or a glass syringe titrate with the thiosulfate solution until solution is perfectly clear and free of any particulates (~2-5 mL).


    Results

      C1 = Volume of thiosulfate added (in mL) to control sample.

      C2 = Volume of thiosulfate added (in mL) to Formaldehyde sample.

     

    Original Manufacturer's formaldehyde stock solution:

      (% w/v)= 15.015*(C1-C2).

    Method contributed by Rick B. Cooley. Graduate Student at the Arp laboratory.