National Biochemicals, LLC.
1780 Enterprise Parkway • P.O. Box 1986, Twinsburg, OH 44087, USA
Phone: 330. 425. 2522 • Fax: 330. 425. 2583
www.nationalbiochem.com
BROMOTHYMOL BLUE
Product No.: MB0128
CAS No.: 76-59-5
Storage Temperature: Ambient
Synonyms: BTB;
3’,3”-Dibromothymolsulfonphthalein
PROPERTIES
HO
Bromothymol Blue acts as a weak acid in solution. It can
thus be in protonated or deprotonated form, appearing yellow
or blue, respectively. It is bluish green in neutral solution.
The deprotonation of the neutral form results in a highly
conjugated structure, accounting for the difference in color.
Br
OH
Bromothymol Blue is sparingly soluble in water, but soluble
in alcohol, ether and in aqueous solutions of alkalis. It is less
soluble in non-polar solvents such as benzene, toluene, and
xylene, and practically insoluble in petroleum ether.1
Br
O
PREPARATION
S
O
O
To prepare a solution for use as a pH indicator, dissolve
0.10 g in 8.0 cm3 N/50 NaOH and dilute with water to
250 cm3. To prepare a solution for use as indicator
in volumetric work, dissolve 0.1 g in 100 cm3
of 50% (v/v)ethanol.1
PRODUCT SPECIFICATIONS
Molecular Formula: C27H28Br2O5S
Molecular Weight: 624.38
Appearance: Dark Red Crystalline
Powder
Clarity of Solution: To Pass
Visual Transition (pH 6.0 to 7.6): Yellow to Blue
PRODUCT DESCRIPTION
Bromothymol Blue is a chemical indicator for weak acids and
bases. It is mostly used in applications that require measuring
substances that would have a relatively neutral pH (near 7),
such as managing the pH of pools and fish tanks. A common
use is for measuring the presence of carbonic acid in a liquid.
USES
Bromothymol Blue may be used for observing photosynthetic
activities, or as a respiratory indicator (turns yellow as CO2 is
2,3
added).
A common demonstration of BTB’s pH indicator
properties involves exhaling through a tube into a neutral
solution of BTB. As carbon dioxide is absorbed from the
breath into the solution, forming carbonic acid, the solution
changes color from green to yellow. Thus, BTB is commonly
used in middle school science classes to demonstrate that the
more that muscles are used, the greater CO2 output.
It may also be used in the laboratory as a biological slide stain.
At this point, it is already blue and a drop or two is used on
a water slide. The cover slip is placed on top of the water
droplet and the specimen in it, with the blue coloring mixed
in. It is sometimes used to define cell walls or nuclei under
the microscope.
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Bromothymol Blue is used in obstetrics for detecting
premature rupture of membranes. Amniotic fluid typically has a
pH > 7.2, Bromothymol Blue will therefore turn blue when
brought in contact with fluid leaking from the amnion. As
vaginal pH normally is acidic, the blue color indicates the
presence of amniotic fluid. The test may be false-positive
in the presence of other alkaline substances such as blood,
semen, or in the presence of bacterial vaginosis.
PRECAUTIONS & DISCLAIMER
This product is solely for Research and Development use.
It is not for drug, household, or any other uses. Please
review the Safety Data Sheet for information regarding
risks and safe handling practices.
REFERENCES
1.
The
Merck
Index,
2.
Sabnis,
R.W.,
3.
Sabnis, R.W., Handbook of Biological
Synthesis and Industrial Applications,
Handbook
of
Entry
#1445,
(2006).
Acid-Base
Indicators,
(2007).
Dyes and Stains:
1st ed., (2010).
NBC warrants that its products will conform with the information provided in this information sheet, though the Purchaser must
determine the suitability of the products for their particular usage needs. Additional terms and conditions may apply.
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MB0128 • 1/29/13 • Rev. 1