Real World: Calcium in Milk

By: Chealsa Mooney and Christina Robinson

• To determine how much calcium was in different types of milk and comparing them to their known values.

• Using two different types of indicators and comparing the results they produce.

Purpose

Procedure OneCalmagite Indicator1.Weighed out EDTA, dissolved in

1000mL. Resulted in 0.0361M EDTA solution

2.Created ammonia buffer3. In 250mL Erlenmeyer flask put 50mL

of milk, 3mL ammonia buffer and small amount of calmagite indicator.

4.Titrated with EDTA solution.

Titration set up withCalmagite Indicator:

Procedure TwoPatton-Reeder1.Used same solution of EDTA.2. In 250mL Erlenmeyer flask put 10mL

of milk, 40mL distilled water, and 4mL of 8M NaOH.

3.Allowed solution to sit for 5 minutes for precipitate to form.

4.Added 0.05g of Patton-Reeder indicator when precipitate formed.

5.Titrated with EDTA solution.

Spike Procedure1. In 250mL Erlenmeyer flask put 10mL

of milk, 3mL ammonia buffer, 1mL spike and small amount of calmagite indicator.

2.Titrated with EDTA solution.3.To test without the spike to see if it

produced the same result we put in a 250mL Erlenmeyer flask 10mL of milk, 3mL ammonia buffer and small amount of calmagite indicator.

4.Titrated with EDTA solution.

DataTypes of milk Percentage of

Calcium• 1% milk 60%• 2% milk 30%• Nonfat skim milk 25%• Lactose milk 50%• Skim milk 45%

DataCalmagite IndicatorEx: Soy milk

Aver: 0.02082g

mL of EDTA Ca2+ conc. (g)

Trial 1 16.8mL 0.02327g

Trial 2 15.2mL 0.02105g

Trial 3 13.1mL 0.01814g

Calmagite indicator color change:

Data

Patton-Reeder IndicatorEx: Soy milk

Aver: 0.02267g

mL of EDTA Ca2+ conc. (g)

Trial 1 19.3mL 0.02673g

Trial 2 13.3mL 0.01842g

Trial 3 16.5mL 0.02285g

Patton-Reeder indicator color change:

DataSpikeEx: Soy milk

spike without spike

Trial 1 18.4mL 17.3mL

Trial 2 18.8mL 17.9mL

Trial 3 18.05mL 17.1mL

CalculationsEX: 1% milk• Ca2+ concentration in milk

L EDTA x M EDTA x 1mol Ca 2+ x molar mass Ca 2+ 1mol EDTA

0.0771 L x 0.0361 M x 1mol Ca 2+ x 40.078 g/mol Ca 2+ =0.11155

1mol EDTA• Grams of Calcium per serving

grams Ca 2+ x volvol sample serving0.11155 g x 240mL = 0.53544 g50mL serving serving

Calculations cont.• Grams of Calcium per serving based on 2,000 calorie

dietmg Ca 2+ (needed daily) x 1 g x %Ca 2+ in milk

1000 mg11oo mg x 1 g x 60% = 0.66g Ca 2+

1000mg

• Percent DifferenceActual - Experimental x 100%

Actual0.66 - 0.5354 x 100% = 18.9%

0.66

Results: Percent Difference

Types: Calmagite Patton Reeder

1% milk 18.6% 26.1%

2% milk 36.9% 12.8%

Nonfat skim milk 102.4% 64.4%

Lactose milk 7.68% 46.2%

Soy milk 79.8% 16.8%

Conclusion- The calmagite indicator took a lot more

EDTA to reach the endpoint -Overall, the Patton-Reeder indicator

produced better results although the lowest percent difference came from the Lactose milk using the Calmagite indicator. (7.68% difference)

-Calmagite indicator with the skim milk produced the highest percent difference (102%)

-The spike test produced good results. It took about that same amount of EDTA to titrate samples with and without the CaCO3

Sources of error:

- misreading the buret - Some trials might have needed to be titrated more (blue endpoint but then after a minute it would go back to purple)

ReferencesDetermination of Calcium Ion Concentration.

College of Science. University of Canterbury, n.d. Web. 12 Dec. 2012.

http://www.outreach.canterbury.ac.nz/chemistry/documents/calcium.pdf

•Harris, Daniel C. Quantitative Chemical Analysis, 8th ed.; W.H. Freeman and Company: New York, 2010, page 240.

Questions ?