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Nigrosin
Saturated: Dissolve 3 g of nigrosin (water soluble)
in 100 mL of DI water. Stir and filter if necessary.
(biological stain for protozoa)
Ninhydrin
Add 2.5 g of ninhydrin to 50 mL of n-butyl alcohol
in a 600-mL beaker. Gently heat and stir the
solution using a magnetic stirrer/hot plate in a
fume hood until all the solid is dissolved. Dilute to
500 mL with n-butyl alcohol. Use extreme caution
when heating n-butyl alcohol, extreme fire risk.
(test for proteins)
m-Nitrophenol
0.3% aqueous: dissolve 0.3 g of m-nitrophenol in
75 mL DI water, then dilute to 100 mL. (pH indicator)
p-Nitrophenol
0.1% aqueous: dissolve 0.1 g of p-nitrophenol in 75
mL DI water, then dilute to 100 mL. (pH indicator)
4-(p-Nitrophenylazo) Resorcinol
Dissolve 0.01 g of 4–(p-nitrophenylazo) resorcinol
in 100 mL of 1 M sodium hydroxide solution
and stir. (indicator solution for magnesium and
molybdenum)
Nutrient Agar
Mix together 23 g of nutrient agar with 1 L of DI
water. Sterilize for 15 minutes at 121 °C (15 lbs of
pressure) in an autoclave or pressure cooker.
Nutrient agar should be sterilized if it is being used
as culture media. Cool to 50–55 °C and pour into
sterilized culture dishes. (culture medium)
Nutrient Agar (using plain agar)
Dissolve 5 g peptone, 3 g meat extract and 15 g of
plain agar in 850 mL of distilled water. Adjust pH
to 7.0. Bring to 1 L with distilled water. Autoclave
or filter sterilize.
Orange G
1% aqueous: Dissolve 1 g of orange G in 75 mL of
DI water, then dilute to 100 mL. Stir and filter if
necessary. (staining plant sections)
Orange IV
0.1% aqueous: Dissolve 0.1 g of orange IV in 75 mL
of DI water, then dilute to 100 mL. Stir and filter if
necessary. (pH indicator and biological stain)
Orcein
Mix together 1 g of orcein, 1 mL of concentrated
hydrochloric acid and 100 mL of 100% ethyl
alcohol. Shake to dissolve, let sit over night and
filter. (stain for elastic fibers)
Pancreatin
Dissolve 5.0 g of pancreatin in 500 mL of DI water,
then dilute to 1 L. Add 0.5 M sodium bicarbonate
solution dropwise until solution is neutral.
(digestive studies)
SAFETY REFERENCE RECIPES FOR SOLUTIONS
Phenantholine
See Ferroin Solution, page 1320.
Phenolphthalein
1% alcoholic: Dissolve 1 g of phenolphthalein in 50
mL of 95% ethyl alcohol, then dilute to 100 mL with
95% ethyl alcohol. For a 0.5% solution, only use 0.5
g of phenolphthalein. (pH indicator)
Phenol Red
0.02% alcoholic: Dissolve 0.1 g of phenol red in 400
mL of 95% ethyl alcohol, then dilute to 500 mL with
95% ethyl alcohol. (pH indicator)
Phenol Red, Sodium Salt
0.02% aqueous: Dissolve 0.1 g of phenol red,
sodium salt in 400 mL of DI water, then dilute to
500 mL. (pH indicator)
Phloroglucinol
Mix 0.5 g phloroglucinol and 50 mL of DI water. Add
50 mL of concentrated hydrochloric acid and stir.
Use within 5–7 days. Always add acid to water. (test
for pentose or galactose)
Polyvinyl Alcohol
4% aqueous: Add 40 g of polyvinyl alcohol to 1 L
of hot tap water. Microwave on high for about 2
minutes; stir and heat for additional 1–2 minute
increments until dissolved. Allow solution to cool
before use. (preparation of “slime”)
Potato Dextrose Agar
Suspend 39 g of potato dextrose agar in 1 L of
DI water. Heat to a boil while stirring constantly.
Boil for 1 minute. Sterilize for 15 minutes at 121 °C
(15 lbs of pressure) in an autoclave or pressure
cooker. Cool to 50–55 °C and pour into sterilized
culture dishes. If using for plate counts of yeasts
and molds, adjust the pH to 3.5 with sterile 10%
tartaric acid. (culture medium for plate counts of
yeasts and molds)
Pyrogallol
Dissolve 80 g of potassium hydroxide in 65 mL of
DI water, add 5 g of pyrogallol, stir, then dilute to
100 mL. Poor shelf life, make fresh. (determining
oxygen content)
Resazurin
1% aqueous: Dissolve 1 g of resazurin in 50 mL
DI water, then dilute to 100 mL. Stir and filter if
necessary. (biological stain and pH indicator)
Richard’s Solution
Dissolve 6.6 g of potassium nitrate, 3.3 g of
potassium dihydrogen phosphate, 33.3 g sucrose
and 1.7 g of magnesium sulfate in 1 L of DI water.
(culture of molds)
Rhodamine B
1% aqueous: Dissolve 1 g of rhodamine B in 50
mL DI water, then dilute to 100 mL. Stir and filter if
necessary. (biological stain)
Ringer’s Solution for Frogs
Dissolve 0.14 g of potassium chloride, 6.5 g of
sodium chloride, 0.12 g calcium chloride and 0.2
g sodium bicarbonate in 1 L of DI water. (mounting
fluid and examination of blood cells)
Ringer’s Solution for Mammals
Dissolve 0.42 g of potassium chloride, 9.0 g of
sodium chloride, 0.24 g calcium chloride and 0.2
g sodium bicarbonate in 1 L of DI water. (mounting
fluid and examination of blood cells)
Rose Bengal
1% aqueous: Dissolve 1 g of rose bengal in 50 mL
DI water, then dilute to 100 mL with distilled water.
Stir and filter if necessary. (biological stain)
Sabouraud Dextrose Agar
Suspend 65 g of sabouraud dextrose agar in 1 L
of DI water. Heat to boiling while stirring. Boil for 1
minute. Sterilize for 15 minutes at 121 °C (15 lbs of
pressure) in an autoclave or pressure cooker. Cool
to 50–55 °C and pour into sterilized culture dishes.
(microbiological culture medium)
Safranin O
Dissolve 0.1 g safranin in 75 mL of DI water, then
dilute to 100 mL. Filter before use. (Gram counter
stain)
Saline Solution
0.75% aqueous: Dissolve 7.5 g of sodium chloride
in 750 mL of DI water, then dilute to 1 L. (Saline
Note: DI water denotes either distilled or deionized water.
RECIPES continued on next page.
Slow Microorganisms
Solutions of methyl cellulose are
commonly
used in microscopy
to slow the
movements of microorganisms—making
them more readily observable. Generally
offered as a 2–3% solution in water, its
high viscosity
physically inhibits the
organism. In use, the resulting dilution will
depend on the amount of water present
on the slide when the slowing agent is
added. Some experimentation may be
required to find the optimal dilution for
a particular organism. One technique
involves dropping the methyl cellulose
onto a clean slide in the form of a ring. A
drop of the culture being studied is then
placed into the center of the ring and a
cover glass applied. As an alternative, see
the listing for polyvinyl alcohol solution.
Recipes for Biological, Histological and Chemical Solutions, continued
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