Real World: Calcium in
Milk
By: Chealsa Mooney and Christina Robinson
Purpose
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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.
Procedure One
Calmagite Indicator
1. Weighed out EDTA, dissolved in 1000mL.
Resulted in 0.0361M EDTA solution
2. Created ammonia buffer
3. 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 with
Calmagite
Indicator:
Procedure Two
Patton-Reeder
1. 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 Procedure
1. 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.
Data
Types of milk
Percentage of Calcium
1% milk
60%
2% milk
30%
Nonfat skim milk
25%
Lactose milk
50%
Skim milk
45%
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Data
Calmagite Indicator
Ex: Soy milk
mL of EDTA
Ca2+ conc. (g)
Trial 1
16.8mL
0.02327g
Trial 2
15.2mL
0.02105g
Trial 3
13.1mL
0.01814g
Aver: 0.02082g
Calmagite indicator color
change:
Data
Patton-Reeder Indicator
Ex: Soy milk
mL of EDTA
Ca2+ conc. (g)
Trial 1
19.3mL
0.02673g
Trial 2
13.3mL
0.01842g
Trial 3
16.5mL
0.02285g
Aver: 0.02267g
Patton-Reeder indicator
color change:
Data
Spike
Ex: Soy milk
spike
without spike
Trial 1
18.4mL
17.3mL
Trial 2
18.8mL
17.9mL
Trial 3
18.05mL
17.1mL
Calculations
EX: 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
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1mol EDTA
Grams of Calcium per serving
grams Ca 2+ x vol
vol sample
serving
0.11155 g x 240mL = 0.53544 g
50mL
serving
serving
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Calculations cont.
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Grams of Calcium per serving based on 2,000 calorie diet
mg Ca 2+ (needed daily) x 1 g
x %Ca 2+ in milk
1000 mg
11oo mg x 1 g
x 60% = 0.66g Ca 2+
1000mg
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Percent Difference
Actual - Experimental x 100%
Actual
0.66 - 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
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)
References
Determination of Calcium Ion Concentration. College of
Science. University of Canterbury, n.d. Web. 12 Dec.
2012.
http://www.outreach.canterbury.ac.nz/chemistry/docume
nts/calcium.pdf
•Harris, Daniel C. Quantitative Chemical Analysis, 8th ed.;
W.H. Freeman and Company: New York, 2010, page
240.
Questions ?