Illustrated Guide to Home Chemistry Experiments

Chapter 19 Laboratory: Qualitative Analysis 349

SBSTITUTIU oNS ANd modIfICATIoNS

• You need a 1.0 g sample of bone. Any type of bone is
  acceptable, including a pork, chicken, or beef bone from
  kitchen scrap. You may also use a sample of bone meal.


• Although all common sodium, potassium, and
  ammonium salts are readily soluble in water, there is
  one exception. Sodium cobaltinitrite is soluble, but
  the potassium and ammonium cobaltinitrite salts
  are insoluble. We’ll use sodium cobaltinitrite in this
  laboratory session to precipitate any potassium ions
  present in the original sample. You can purchase
  sodium cobaltinitrite, but it’s just as easy and less
  expensive to synthesize it yourself. To do so, dissolve
  25.0 g of sodium nitrite in 75 mL of water. Add 2.0
  mL of concentrated (glacial) acetic acid. Add 2.5 g of
  cobalt nitrate hexahydrate, and stir until the cobalt salt
  dissolves. Allow the solution to stand for a few days,
  filter out any solid precipitate, and dilute the solution
  to 100.0 mL.

LABORATORY 19 .5:

qUALITATIvE ANALySIS of BoNE

Animal bone is a complex structure that

incorporates both organic and inorganic

components. Most of the inorganic component,

which makes up about 70% of bone mass,

is hydroxylapatite, which is produced by the

body but also occurs naturally as a mineral.

Hydroxylapatite has the empirical formula

Ca 5 (PO 4 ) 3 (OH), but the formula is usually

written as Ca 10 (PO 4 ) 6 (OH) 2 , because the

crystalline structure of hydroxylapatite is

bimolecular. In bone, the hydroxyl ion is

sometimes replaced by chloride, carbonate,

or other anions. Other inorganic and organic

components of bone include smaller amounts

of other anions and cations.

RIREEqU d EqUIpmENT ANd SUppLIES

£ goggles, gloves, and protective clothing

£ balance and weighing papers

£ beaker, 150 mL (2)

£ graduated cylinder, 10 mL

£ eye dropper or Beral pipette (5)

£ test tubes (6)

£ test tube rack

£ test tube clamp

£ gas burner

£ ring stand

£ support ring

£ wire gauze

£ inoculating loop

£ stirring rod

£ funnel and filter paper

£ litmus paper (red and blue)

£ bone sample (see Substitutions and modifications)

£ nitric acid, 6 m (~30 mL)

£ silver nitrate, 0.1 m (a few mL)

£ barium chloride, 0.1 m (1 mL)

£ ammonium molybdate, 0.1 m (5 mL)

£ ammonium oxalate, 0.2 m (15 mL)

£ potassium thiocyanate, 0.1 m (a few drops)

£ hydrochloric acid, concentrated (~1 mL)

£ sodium hydroxide, 6 m (5 mL)

£ sodium cobaltinitrite reagent (see Substitutions and

modifications)

In this laboratory, we’ll apply what we’ve learned in the
preceding lab sessions to analyze a sample of bone for several
anions and cations.