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Alternative to distilled water for pH test

Alternative to distilled water for pH test


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I am looking to test soil pH in a remote location. The test results don't need to be perfectly precise, and a pH test strip should provide sufficient accuracy. However generally this kind of testing uses boiled distilled water - and in this location it will be very difficult to buy distilled water.

The location is off grid, and getting specialized equipment to the location is not an option. (This is for field experimentation with farmers in rural Africa)

The process I have seen used for this is:

  • Add 1 part boiled distilled water and 1part soil by volume, in a clean container
  • stir and leave to settle.
  • Test the water pH with a pH test strip

Would it be possible to use boiled rain water for this process, or would this be likely to contain impurities which would interfere with the test results?

If there are likely to be impurities but there are approaches that can mitigate for them, please explain.


Rainwater might not be the best option.

Rain water is naturally acidic due to the reaction of CO2 forming some weak carbonic acid [see here for explanation].

Source: Wikipedia

As a result, pH of "pure" rainwater is usually between 5-6; usually around pH 5.6. See here.

Most rainwater has a pH of 5.6 to 5.8, simply due to the pressence of carbonic acid (H2CO3).

Presence of any sulfur or nitrogen oxides in the air (perhaps from burning coal plants or city traffic from 100s of km away) would lead to rain becoming even more acidic. From environment.co.za:

Sulphur dioxide reacts with water vapour and sunlight to form sulphuric acid. Likewise NOX form nitric acid in the air. These reactions takes hours, or even days, during which polluted air may move hundreds of kilometres. Thus acid rain can fall far from the source of pollution.


The h2co3 content of unadulterated rain is 15 micromoles of H+/Kg at room temp. The pHBC of average field soil from a 3000km transect in asia varied from 10 to 188 - mmol-kg-ph unit… from 40 localities. This other research found soil values of 45-1000 pHBC. https://www.science.gov/topicpages/s/spiked+soil+samples.html

That means that H2CO3 would affect arid meadow soil by 0.08 to 1.0 pH points if 1kg of water reacted completely with 1kg soil in a sealed environment. And 0.33 to 0.015 pH points for the referenced research.

However, if you boil the water, the gases expand and leave the water even prior to boiling point, which can be seen as bubbles previous to 100'C, boiled water error becomes 0.2 to 0.003 pH points. This is the only ref i can find:

biol-2022/6608/image_AzTOhdSOids9ny2mRfZZE8t6.png">https://books.google.fr/books?id=yRMgYc-8mTIC&pg=PA124&lpg=PA124&dq=hcl%20micromole%20co2%20distilled%20water%20concentration&source=bl&ots=OFKb4CB3MI&sig=ACfU3U0a1XQ_GSIZ5E-nj7JgPsaeDv7SbA&hl=en&sa=X&ved=2ahUKEwib-vuMkc_hAhVEThoKHYIcDtQQ6AEwCXoECFAQAQ#v=onepage&q=hcl%20micromole%20co2%20distilled%20water%20concentrationhcl&f=false


Alternative to Practical Paper

Related Topics:
More Lessons for IGCSE Chemistry
Math Worksheets

A series of free IGCSE Chemistry Activities and Experiments (Cambridge IGCSE Chemistry).

Questions
Solid E was analysed. E was an aluminium salt. Some of the observations are shown below.
Appearance of solid E - white crystalline solid.
Test 1:
A little of solid E was heated in a test-tube - colourless drops of liquid formed at the top of the tube.
(a) A little of solid E was dissolved in distilled water.
The solution was divided into four test-tubes and the following tests were carried out.

Complete the observations for tests 2 and 3.
(i) Test 2:
Drops of aqueous sodium hydroxide were added to the first test-tube.
observations ________________________[1]
(ii) Excess sodium hydroxide was then added.
observations ________________________[1]
(iii) Test 3:
Drops of aqueous ammonia solution were added to the second test-tube. Excess ammonia solution was then added.
observations ______________ [2]

Two further tests are carried out and the following observations made.
tests on solution of E observations
Test 4:
To the third test-tube of solution, dilute hydrochloric acid was added, followed by barium nitrate solution - no reaction
Test 5:
To the fourth test-tube of solution, aqueous sodium hydroxide and aluminium foil were added.
The mixture was warmed carefully - effervescence, pungent gas given off, gas turned damp litmus paper blue
(b) What does test 1 tell you about solid E? __________[1]
(c) Identify the gas given off in test 5. __________ [1]
(d) What conclusions can you draw about solid E? __________ [2]
(e) Test 5 states that the mixture should be warmed carefully.
In terms of safety, explain why it is necessary to warm carefully _________ [2]

Questions
E-numbers identify chemicals which are added to foods.
(a) E210 is benzoic acid. How could you show that a solution of benzoic acid is a weak acid?
test
result __________ [2]
(b) E110 is Sunset Yellow.
Outline a method you could use to show the presence of E110 in a food colouring.
You may draw a diagram to help answer the question. [4]

Try the free Mathway calculator and problem solver below to practice various math topics. Try the given examples, or type in your own problem and check your answer with the step-by-step explanations.

We welcome your feedback, comments and questions about this site or page. Please submit your feedback or enquiries via our Feedback page.


Acid Base Reactions & pH Experiments

Experimenting with acids and bases can make for exciting chemistry projects!

Acidic solutions have a higher concentration of hydrogen ions (H+).

These are hydrogen atoms that have lost an electron and now have just a proton, giving them a positive electrical charge.

Basic solutions, on the other hand, contain hydroxide ions (OH-). One of the simplest activities to show how acids and bases react with each other (and to demonstrate their different properties) is to make a vinegar and baking soda volcano.

For another reaction experiment, put an Alka-Seltzer tablet in the bottom of a clear plastic film canister (the kind where the cap fits inside instead of closing over the outside).

Fill the canister with warm water and then quickly put the cap on and watch the acid-base reaction!

The pH scale is used to measure how acidic or basic a solution is. Acids have a pH below 7 bases have a pH above.

Neutral solutions (like distilled water) with a balanced number of H+ and OH- ions have a pH of 7. Do the following projects to explore the cool effects of pH.

Litmus is a natural acid-base indicator extracted from a type of lichen. If you have red and blue litmus paper, you can test different solutions for whether they are acids or bases.

Blue litmus paper turns red when a solution is acidic red litmus paper turns blue in basic solutions.

Try testing window cleaner, toilet bowl cleaner, orange juice, and apple juice—pour a little of each into separate test tubes or small glasses or jars.

Use the litmus paper to determine which are acids and which are bases. Here are the pH levels of some other substances that you might test:

  • Lemon juice (2)
  • Vinegar (3)
  • Milk (6)
  • Egg whites (8)
  • Baking soda (9)
  • Ammonia (10)

Human blood has an ideal pH of 7.4 even slight fluctuations can seriously affect our bodies.

You can also make your own pH indicator—use a blender to mix one part chopped red cabbage with two parts boiling water and use the juice to test different solutions.

Acids will turn the pigments in the indicator to a reddish color bases will turn the pigments bluish or yellow-green.

Mystery Pitcher

Make ordinary water turn bright pink and then back to clear! This makes a great “magic trick” to impress your friends – just be careful no one mistakes it for fruit punch and drinks any!

>> Check out our project video to see this trick in action!

What You Need:

What You Do:

  1. In the first glass put a little less than 1/8 teaspoon of sodium carbonate, in the second put 6 drops of phenolphthalein solution, and in the third put three droppers-full of vinegar.
  2. Add a few drops of water to the first glass and stir to dissolve the sodium carbonate.
  3. Fill all the glasses with water from the pitcher, then pour all of them back in the pitcher except for the glass with vinegar.
  4. Refill the remaining four glasses – the water will be red!
  5. Now pour all five glasses back in the pitcher. Refill the glasses one last time—the liquid will be colorless again!

What Happened:

Phenolphthalein is a pH indicator, but it only turns colors in reaction to bases. When you poured the four glasses back into the pitcher, the phenolphthalein reacted to the sodium carbonate, a base, and turned the solution to bright pink “kool-aid.” To change it back to “water,” all you had to do was add the acidic vinegar, which turned the phenolphthalein colorless again.

Featured Kit
Chemistry Magic Tricks Kit With this cool experiment kit, you’ll be able to make color-changing solutions and even turn water into a solid instantly! The 12 chemistry tricks in this kit will amaze your friends plus teach about the science of pH, acids and bases, density, chromatography, and polymers. This set includes high quality chemistry equipment, like glass beakers and a graduated cylinder, as well as three chemicals to make two kinds of invisible inks, turn ordinary water bright red, make a colorful rainbow in a tube, and much more.

Rainbow Reaction Tube

Amaze your friends by mixing two solutions to make a rainbow!

Watch as purple sinks to the bottom and red floats to the top, and they mix together to form every color in between.

What You Need:

What You Do:

  1. Put 15 drops of universal indicator in the graduated cylinder and add filtered water up to the 10 ml mark. The solution should be yellow-green.
  2. Add 3 drops of vinegar to the solution in the graduated cylinder, and it should turn red.
  3. In a beaker, put two scoops of sodium carbonate and then add about 30 ml of water. Mix together with the stirring rod until the sodium carbonate dissolves. The solution should be clear.
  4. To start the reaction, fill one dropper full with sodium carbonate solution. Squeeze the dropper into the graduated cylinder quickly, rather than drop by drop. The clear solution should instantly turn dark purple, and slowly sink to the bottom, swirling around to make the rainbow.
  5. Let the contents of the cylinder settle, until you can see each color from bluish-purple to red. To make the rainbow disappear, pour it into an empty beaker, and it should turn yellow or yellowish green.

What Happened:

Universal indicator changes colors to show the pH level of a substance. In this case, when you mixed an acidic solution (vinegar) with a basic one (sodium carbonate), the indicator made a colorful spectrum — from dark blue to red. Interestingly, if you had added the solutions in the opposite order, you would not have seen a rainbow. To get the rainbow effect, another scientific principle is at work—density. The sodium carbonate solution you made is denser than the indicator solution, so it sinks to the bottom. As the sodium carbonate solution makes its way to the bottom, some of its molecules mix with vinegar molecules, making a new solution, which shows up as a color of the pH scale.

If you don’t turn the graduated cylinder upside down, the rainbow will last several days. Over time the colors will mix together through the process of diffusion. The molecules of each solution will mix throughout the graduated cylinder, rather than staying concentrated at the top or bottom. Once you mix the acid and base solutions together, the solution will be pH neutral, and look yellow or slightly green.

To make a different kind of rainbow tube, try making this rainbow density column with all household materials.


How to Make Homemade pH Paper Test Strips

This article was co-authored by Bess Ruff, MA. Bess Ruff is a Geography PhD student at Florida State University. She received her MA in Environmental Science and Management from the University of California, Santa Barbara in 2016. She has conducted survey work for marine spatial planning projects in the Caribbean and provided research support as a graduate fellow for the Sustainable Fisheries Group.

wikiHow marks an article as reader-approved once it receives enough positive feedback. This article received 13 testimonials and 82% of readers who voted found it helpful, earning it our reader-approved status.

This article has been viewed 472,221 times.

The pH scale measures how likely a substance is to give up protons (or H + ions) and how likely that substance is to accept protons. Many molecules, including dyes, will change their structure by either accepting protons from an acidic environment (one that readily gives up protons) or donating protons to a basic environment (one that readily accepts protons). Testing for pH is an essential part of many chemistry and biology experiments. This test can be done by coating paper strips with dyes that will change into different colors in the presence of an acid or a base.


Diabetes mellitus is a disease that refers to the inability of the cells to take in glucose. The word diabetes refers to urination and mellitus refers to sweetness. Since the cells of diabetics cannot remove glucose from the blood, there is an excess of glucose circulating that is eliminated in the urine. The traditional method of diagnosing someone with diabetes mellitus was to taste the sweetness of the patient’s urine. Let’s use Benedict’s test for the detection process instead of the unhygienic alternative.

Make a hypothesis and ask what we would predict from a Benedict’s test if testing a urine sample of someone with diabetes mellitus.

Activity: Benedict’s Test For Reducing Sugars

Obtain 9 test-tubes and number them 1-9.

Add to each tube the materials to be tested. Your instructor may ask you to test some additional materials. If so, include additional numbered test tubes.

Indicate in the table whether the the sample you are testing is positive control, a negative control or an experimental.

Before you begin the heating of the samples, use predict the color change (if any) for each sample. (use the sample type to aid in your prediction)

Add 2 ml Benedict’s solution to each tube.

Place all of the tubes in a boiling water bath for 3 min or until a noticeable color change and observe colors during this time.

After 3 min, remove the tubes from the water bath and let them cool to room temperature. Record the color of their contents in the Table.

Table:Solution And Color Reactions For Benedict’s Test For Reducing Sugars


  • Use your senses and previous observations/experiences about the qualities of the experimentals.
  • Formulate some hypotheses about the carbohydrate content of the experimentals or unknowns.
    • Identify if the sample is experimental or control before making hypothesis

    Diabetes mellitus is a disease that refers to the inability of the cells to take in glucose. The word diabetes refers to urination and mellitus refers to sweetness. Since the cells of diabetics cannot remove glucose from the blood, there is an excess of glucose circulating that is eliminated in the urine. The traditional method of diagnosing someone with diabetes mellitus was to taste the sweetness of the patient&rsquos urine. Let&rsquos use Benedict&rsquos test for the detection process instead of the unhygienic alternative.

    Make a hypothesis and ask what we would predict from a Benedict&rsquos test if testing a urine sample of someone with diabetes mellitus.


    Testing the pH of Soil Samples

    Commercial and recreational gardeners are showing a growing interest in taking accurate pH measurement of soil samples . The pH of soil indicates more than its alkalinity or acidity strength it affects the relative availability of nutrients, the soil life, and the type of plants that will thrive.

    The common range of soil pH varies from 4.0 to 8.0 the range of soil pH for optimal availability of plant nutrients is 6.0 to 7.0. The ability of soil to provide adequate nutrition to the plant depends upon the following factors :

      Essential elements in the soil—The nutrients present in soil depend upon the elemental nature of the soil and the organic material content. Soil nutrients exist both as complex insoluble compounds (organic materials) and as simple soluble forms.
      Release of nutrients to plants—Simple elements in the soil are readily available for plant uptake. The complex forms (organic materials) must be broken down through decomposition to simpler, more available forms to benefit the plants.
      pH of the soil solution—pH directly affects the availability of essential nutrients. For example, though iron, manganese, and zinc become less available as the pH rises above 6.5, molybdenum and phosphorus become more available. When the soil is acidic, minerals such as zinc, aluminum, manganese, copper, and cobalt become more soluble for plants’ uptake. However, an excess of these ions can be toxic to plants. Alkaline soil contains a higher quantity of bicarbonate ions, which interferes with the normal uptake of other ions, harming plant growth.

    Soil life refers to living organisms that live in the soil and break down the organic materials. Soil bacteria that assist in the decomposition of organic material thrive at a pH of 6.3 to 6.8. Fungi and mold prefer a more acidic soil, making soil more prone to souring and putrefication.

    Plants also have different soil pH preferences—several gardeners’ web sites offer charts of preferred pH levels for different plants. Knowing the pH of soil can help you choose the correct plants and the required treatment for your soil.


    Red Cabbage Juice: A Homemade pH Indicator!

    In the laboratory, pH paper and chemicals are commonly used to indicate pH. In the homeschool, students can make their own pH indicator using red cabbage juice, which changes color in the presence of an acid or base. The plant pigment anthocyanin is the active ingredient responsible for the color change. In this activity, students make a pH indicator from red cabbage juice and then use it to test various substances.

    Materials

    • Red cabbage leaves
    • 200 mL water
    • Blender
    • Strainer
    • 250-mL beaker or clear container
    • Medicine droppers (1 per test substance)
    • Sheet of white paper
    • 50-mL beakers or clear containers, (1 per test substance)
    • 1 mL vinegar
    • 1 mL household ammonia
    • Test substances, 1 mL of each (e.g., lemon juice, fruit juice, milk, detergent, soda, antacid tablets, baking soda)

    Procedure

    1. Put on apron, gloves, and eye protection.
    2. Chop up several red cabbage leaves.
    3. Place the leaves in a blender and add 200 mL water.
    4. Blend the mixture and then pour it through the strainer into the large beaker or container. The red cabbage juice indicator is now ready for use. Note: If you use distilled water the indicator will have a reddish purple color and if you use tap water the indicator will have a violet blue color.
    5. Fill each of the small beakers or containers with 10 mL of indicator. Place them on the white sheet of paper.
    6. Add a few drops of vinegar to one container and a few drops of ammonia to another. Vinegar is an acid and ammonia, a base. Vinegar turns the indicator red and ammonia turns it green. Use these 2 samples as references for the other test substances.
    7. Test each substance by adding a few drops of it to a container of indicator. To test an antacid tablet or other solid, crush it, dissolve it in water, and add a few drops of the resulting solution to a container of indicator. After testing all the substances, students’ results should display a beautiful array of colors ranging from green to blue green, blue, violet, and red. See how the colors correspond to approximate pH ranges in the table below.
    Approximate pH Range 1 to 5 6 to 7 8 to 9 10 to 11 12 to 14
    Color Red Violet Blue Blue green Green

    Extension

    Students can also make paper pH indicator strips using red cabbage juice. Here’s how to do it. First, cut strips from an unused paper coffee filter. Next, soak them in red cabbage juice for several hours. Finally, take the strips out of the juice and allow them to dry completely. Once the indicator strips are dry, they are ready for use. The dried strips will be light violet or pale blue in color. Simply dip an indicator strip in the substance you’re testing, remove it, and look for a color change. Acids will turn the strips red and bases will turn them green.

    Conclusion

    Red cabbage juice indicator changes color because its hydrogen ion concentration changes when a test substance is added to it. Acids produce hydrogen ions in aqueous solution and have a pH less than 7. Bases contain hydroxide ions and have a pH greater than 7. At a pH of 7, a substance is neutral (neither acid nor base) due to equal numbers of hydrogen and hydroxide ions. Carolina offers a full line of kits, chemicals, and pH indicators to further your exploration of pH.

    Additional resources

    You May Also Like


    Maker Challenge Making Dirty Water Drinkable!

    Water is a critical and necessary need for life to exist. Clean water is especially critical to humans.

    Maker Challenge Recap

    Access to clean water is a major problem we face in the world today, especially in developing countries and during, and in the aftermath of, natural disasters. Currently, there is a portable water purification device called the LifeSaver bottle that can bring clean water to people however, it is too expensive for most individuals. In this maker challenge, students work through the engineering design process.  They create a water bottle from commonly available materials used in purification tools, that can assist in cleaning dirty water as an inexpensive alternative to the LifeSaver Bottle.

    Maker Materials & Supplies

    Note: Most supplies are available online or in a local hardware store.

    • Materials to build the water bottle:
      • different types of plastic water bottles (these can be recycled items brought in from home)
      • coffee filter paper
      • Whatman filter paper, available online
      • mesh (several different varieties thin and heavy duty)
      • hot glue guns and glue sticks
      • scissors
      • rubber bands
      • air conditioning filter paper
      • Types of water cleaning media:
        • granular activated carbon, available online
        • Zeolite, available online
        • Equipment for water quality test:
          • pH meter or pH strips, available online
          • beaker
          • water quality test strips
          • dirty water (either from a local water source or handmade)
          • distilled water

          Worksheets and Attachments

          More Curriculum Like This

          Filtering is the process of removing or separating the unwanted part of a mixture. In signal processing, filtering is specifically used to remove or extract part of a signal, and this can be accomplished using an analog circuit or a digital device (such as a computer). In this lesson, students learn.

          Kickoff

          [Begin the maker challenge by showing students the TED video “Michael Pritchard: How to make dirty water drinkable”. Pause the video at 1:10 before the introduction to the LifeSaver water bottle to discuss possible water contaminants and their sources.]

          What are some possible water contaminants and their sources? [Write down student responses on the board as the students share their thoughts. Resume the video to show them a solution that can bring clean water to people in need.]

          How does the LifeSaver water bottle work? The LifeSaver bottle is a portable water purification device that filters out particles and objects bigger than 15 nm—including viruses, bacteria, cysts, fungi, parasites and other microbiological pathogens in water. To filter the water, contaminated water is poured into the water bottle and the user manually pumps up the bottle. This pumping creates pressure that pushes the water through a nanofilter. The clean water collects in a separate chamber of the bottle and an individual can then drink the safe drinking water out of the top. The whole filtering process takes about 20 seconds, and the bottle has an interchangeable filter that filters 0.71 L (1.5 pints) of water at a time, purifying up to 6,000 L over the course of its lifetime.

          There is a larger version of the LifeSaver bottle, called the LifeSaver Jerrycan. It uses the same filtering technology but it can filter 10,000 to 20,000 L over the course of its lifetime. One LifeSaver Jerrycan filter can provide water for four people for three years!

          Now, how much do you think that water bottle costs? [After a couple of guesses, tell the students that it costs $150!] What do you think about that? Do you think that is an affordable piece of technology?

          Today you are going to play the role of engineers and create a water bottle similar to the LifeSaver that can clean dirty water with common items used in purification. You will be tasked with developing a prototype and then iterating to improve upon it.

          Resources

          • Refer to the Engineering Design Process hub on TeachEngineering to guide your students through the challenge.
          • TED Talk: “Michael Pritchard: How to make dirty water drinkable”: https://www.youtube.com/watch?v=rXepkIWPhFQ&feature=youtu.be
          • An explanation of how spectrophotometers analyze samples: “The Spectrophotometer: A demo and practice experiment": https://www.youtube.com/watch?v=xHQM4BbR040

          Maker Time

          • Students will work in teams of four to develop their own prototype of a water bottle that cleans dirty water. They may run tests on any of the materials before building to become familiar with them in order to decide if they are going to use them in their design.
          • Students may do initial sketches of their design and draw their final design on the Student Worksheet. The teacher should check the design and offer suggestions, if necessary.
          • Students build their water bottle and run some water quality tests to see how well it worked.
          • The students record the general characteristics of the water (transparency, color), pH (should be close to seven for clean water). Students may also use a water quality test strip to test for bacteria and other pollutants that are invisible to the naked eye. (See “Tips” below for incorporating a spectrophotometer into the activity, if one is available for use.)
          • Students will also test the dirty water to be able to compare and make a judgment about the efficiency of their water bottle.

          Wrap Up

          • A student representative from each group will display their water bottle and summarize the results of their test.
          • Once each group has presented, students may alter their designs based off their experiments and the designs of their classmates. The may retest to see if their new design improved the ability to clean the dirty water. If there is limited time, you may ask students to collaborate and design a water bottle as a class.
          • The students discuss the parts of the water bottle that they liked from each group and a class design. Students reflect on their learning by writing a summary of what they have learned about water pollution, the effects of dirty water on human health, and their engineering design process.

          If you are in a laboratory that has access to a spectrophotometer, view the video, “The Spectrophotometer: A demo and practice experiment” from YouTube to help you.

          • Turn on the spectrophotometer and click on the wavelength button (ƛ). Select 1 wavelength and enter in 600 for the nm length. Press ENTER. Select “NO” for background reading. Fill a blank cuvette with distilled water. Clean off the sides and put the cuvette in the spectrophotometer with the smooth side facing the arrow. Press “READ BLANK” and the value should come back as 0.0 AU. Your spectrophotometer is now ready for student samples. Have students record their reading when it appears.

          Copyright

          Contributors

          Supporting Program

          Acknowledgements

          This curriculum was based upon work supported by the National Science Foundation under Rice University Engineering Research Center for Nanotechnology Enabled Water Treatment Systems (NEWT) RET grant no.1449500. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation.


          Description

          Measuring the pH of fermented sausages is necessary for food safety and proving process control. Watch and learn how to measure the pH of these products accurately.

          Individuals wanting to learn more about measure pH of various types of meat products.

          Different electrodes and meters used to measure pH in meat products and how to properly care for them to maintain accuracy.

          Instructors

          More by Jonathan A. Campbell, Ph.D.

          View Transcript

          - [Instructor] This instructional video will teach you how to incorporate rapid quality measurements into your small-scale processed meat manufacturing establishment.

          Keeping product quality parameters consistent can lead to increased sales by ensuring more repeat business and expanding your customer base through improved brand reputation.

          In this video, we will discuss various methods of measuring pH.

          There are many different types of devices used to measure pH.

          Meat products are unique when measuring how acidic or basic a sample is.

          Choosing the correct electrode and meter combination is critical in gaining accurate results.

          Portable and bench top pH meters will be discussed and demonstrated during this second learning objective.

          Fermenting sausage products in the olden days was inconsistent, resulting in product that varied from day to day in terms of sensory and quality attributes.

          As a general rule, product formulations were not written down and measuring pH to determine if fermentation was successful was non-existent.

          Employees measuring pH should always wear eye protection, a lab coat, or apron, as well as non-latex gloves and close-toed shoes.

          Accuracy of measuring pH is often affected by traces and conditions that could be changed to increase the accuracy of the results, for example, temperature of the sample being measured or the electrode used to measure the pH.

          This segment will demonstrate and discuss choosing the appropriate pH meter and electrode for various products to be examined for pH.

          First, you need to decide what level of financial flexibility your facility has to spend on a pH meter and electrode and how portable the meter needs to be.

          If you are measuring cold samples, consider utilizing an electrode that calculates and compensates for differences in temperature.

          The meter chosen should measure in the hundredths place and the accuracy should be at least plus or minus two hundredths.

          Most pH meters have an automatic calibration function.

          As long as the automatic process continues through to completion, the results of the calibration will be more useful than trying to calibrate your apparatus manually.

          When calibrating your meter, be sure to use fresh buffers in the appropriate range for what you are measuring.

          Typically, for meat products, the meter should be calibrated with pH buffers 4.01 and 7.00.

          Unless the meter has a temperature compensating probe or function, the buffers should be used at room temperature or approximately 25 degrees celsius.

          Bench top meters tend to be a greater financial investment although some portable machines can be very costly.

          Bench top meters are very useful if your facility has a dedicated area or lab to measure the pH of larger quantities of a variety of samples.

          The electrode is the portion of the meter that is actually inserted into the meat sample or solution being measured.

          Some electrodes are specific to measuring only liquids, some measure surfaces of products and some are able to be used on a variety of sample types.

          Portable meters are ideal for the cost-savvy individual or where pH measurements need to be made in a variety of locations in your facility.

          When deciding upon the appropriate meter for your needs, consider more than just the costs of the meter.

          Items to consider when choosing a portable meter include the sensitivity of accuracy, the pH range of the meter and if the meter is able to compensate for temperature.

          When measuring meat samples, choose a location that will be representative of the product being measured.

          To increase the accuracy of measurements, consider taking duplicate measurements and averaging the results.

          In this example, notice that the probe placement in the approximate geometric center of the sausage was chosen as a representative location.

          To duplicate the measurement, the sausage was cut in half and both halves are being measured.

          Since pH is the measure of acidity of a solution, dry meat products may pose a difficulty when measuring the pH.

          Dry samples are often a problem, especially if the electrode chosen has a glass tip.

          Dry meat samples can cause damage to the electrode, which is often a very costly investment to replace.

          Consider pulverizing dry samples in a sample homogenizer, making a one to four solution of the meat sample and buffered peptone water.

          For example, a dry sausage with low moisture to protein ratio, may be too hard to accurately sample for the electrode on your meter.

          Weigh five grams of the sample in a filter bag, add 15 milliliters of buffered peptone water, and pulverize the sample for two minutes prior to measuring the pH of the solution.

          This will allow for measuring the pH of your product without causing damage to your investment.



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