Illustrated Guide to Home Chemistry Experiments

Chapter 19 Laboratory: Qualitative Analysis 351

7.ip the end of the platinum or Nichrome inoculating D

loop into concentrated hydrochloric acid and then hold

it in the gas burner flame until the loop adds no color

to the gas flame. Dip the clean loop into the sample,

and then hold it in the gas flame. A bright yellow flame

coloration confirms the presence of sodium ions in the

sample. Record your observations on line F of Table 19-6.

8. Transfer 5 mL of the sample to the sixth test tube. Add
   3 mL of 6 M sodium hydroxide solution to the test tube
   and mix thoroughly. Carefully sniff the test tube by using
   your hand to waft any vapors from the mouth of the test
   tube toward your nose. An odor of ammonia confirms

dISpoSAL: dispose of all waste materials by flushing

them down the drain with plenty of water.

the presence of ammonium ion in the sample. If no odor

is obvious, gently warm the test tube for a minute or so,

periodically testing for the scent of ammonia. Record

your observations on line G of Table 19-6.

9. Continue heating the test tube until it comes to a very
   gentle boil. Continue the gentle boil for a minute or
   two to drive off all of the ammonium ions as gaseous
   ammonia. Allow the test tube to cool and then add about
   3 mL of the sodium cobaltinitrite reagent. A precipitate
   of insoluble potassium cobaltinitrite confirms the
   presence of potassium ions in the sample. Record your
   observations on line H of Table 19-6.

TABLE 19-6: Qualitative analysis of bone—observed data

Ion Reagent Observations

A. Chloride(Cl–) Silver nitrate

B. Sulfate (SO 4 2–)Barium chloride

C. Phosphate (PO 4 3–)Ammonium molybdate

D. Calcium (Ca2+)Ammonium oxalate

E. Iron(III) (Fe3+)Potassium thiocyanate

F. Sodium (Na+) Flame test

G. Ammonium (NH 4 +)Sodium hydroxide

H. Potassium (K+)Sodium cobaltinitrite