Download acids and bases - Althea`s Academy

Dr. Althea R. Arenajo
Conncepts:
1. Arrhenius concept (classical)
acids- subs which contain H and when
dissolved in water will furnish H1+
base – subs which contain OH group and
when dissolved in water, will furnish OH12. Bronsted-Lowry Concept (protonic
concept of acidity)

acids- subs, molecule, ion capable of
giving up a proton to another subs
base – subs, molecule, ion capable of
combining with a proton
3. Lewis concept
acid- any specie that can accept a a
pair of electrons
base – any specie that can donate a
pair of electron
Lewis acids are often termed electrophilic
because the acidic property maybe looked
upon as a ‘seeking’ of electrons from the
electron donating base
Hyrogen-ion cocentration or pH
H+ = hydrogen ion, a symbol representing
the loss of the one and only electron
 Strictly speaking, H is a proton
 Responsible for the acidic nature of subs

Aprotonic solvents – subs that do not
accept proton, do not behave as acids
Hydroxide ion (OH-) – a radical composed
of a hydrogen atom, an oxygen atom and
an electron giving it a neagtive charge
 Responsible for the chemical properites
of alkali
Amphoteric subs – subs that may act as
acid or base
Pure water is always neutral, it contains
same hydronium and dhydroxide ions
Hydronium ion conc – represents the
actual acidic intensity of a sol’n
Expression of H3O+ conc in aq sol’n is
considered as being limited by the
ionization constant of water to a range
of bet 1x100 and 1X1014
 Nornal limit of pH are given as 0 to 14

Classification of acids:
a. Strong acids- are highly ionized
ex: HCl, HNO3, H2SO4,
b. Weak acids- ionized only slightly
ex: HCN, H3BO3, organic acids
Three methods for the det of H3O+conc:
1. Colorometric method - utilizes reagents
called indicators

Indicators – are weak organic acids or
bases in which the undissociated
molecule has one color and the anion
or cation produced by dissociation has
another color
Indicators
bromophenol blue
bromocresol green
Acid
Base
yellow
yellow
blue
blue
methyl orange
red
yellow
methyl red
red
yellow
phenol red
yellow red
cresol red
yellow red
phenolphthalein colorless red
thymol blue
colorless blue
2. Potentiometric – based upon measuring
the voltage developed when electrode is
immersed in solution
This method is preffered by the USP
because of its accuracy, rapidity, and
flexibility that can be used in turbid and
jelly-like solutions and those contg
pigments and proteins
3. Chemical method – is only for scientific
interest and not used practically as a
method for determining pH


A variation of the colorimetric method
which is more practical includes strips of
paper impregnated with an indicator
◦ Merely dipping the paper in the unknown
sol’n produces a color on the paper
which can be compared with charts
supplied by the manufacture
◦ This is of value to diabetic patients for
testing the actual acidity of the urine

Examples of these paper:
a. Nitrazine paper (Squibb)
b. pHydrion paper (Central Scientific Co.)
c. Alkacid test ribbon ( Fisher Scientific)
d. Accutint paper ( E.H. Sargent & Co)
e. Special pH paper Paul Frank N.Y.)
f. Universal pH Indicator paper (BraunKnecht-heimann Co)
g. Oxyphen paper(J. Einstein Co)
Buffer – a pair of chemical compound
which control a change in pH of sol’n
 Factors that cause variation in H+ conc:
a. Alkali in the Glass from cheap bottles
b. Gases as CO2, Cl2 and NH3 in the air
c. Dust particles
d. Oxidation
e. Introduction of medicinal agents

Controlling pH is impt in the ff:
a. Collyria
d. Vit prep
b. Oral penicillin
e. Alkaloidal sol’n
c. Milk of magnesia f. Parenteral sol’n
 A buffer mixture (or buffer pair) is a sol’n
composed of weak acid and a salt of the
weak acid or a weak base and its salt
 A buffer sol’n will resist any great change
in pH


Buffer system in common use:
a. Feldsman’s buffer (pH range 7.0-8.2)
H3BO3 & Na2B4O7
b. Atkins and Pantin Buffer (7.6-11.0)
H3BO3,Na2CO3 & NaCl – useful in the
alkaline range for contact lens sol’n
- introduced the best buffer system
c. Gifford’s buffer (pH range 6.0-7.8)
- slight modification of Atkins/Patin



Replaced potassium chloride for sodium
chloride and arranged the volumes on a
basis of 30 mL
Borate buffers have a buffer range of
from Ph 5 to 11 with greatest capacity at
pH 9
Suitable for ophthalmic, nasal, and
exteral application but not for parenteral
d. Sorensen Phosphate Buffer (pH range
4.5 -8.0) has a greatest capacity at
6.7
- valuable buffer system for the eyes,
pH includes the isohydric point of
tears (pH 7.4)
 Buffers are used in numeral ways in
pharmaceuticals: antacids, ointments
and lotions
Official Inorganic Compounds
1. Boric Acid – Sal Sedativum Hombergi
 Free Boric acid is found in sea water,
certain plants, and nearly all fruits
 Found in th emarket in three forms:
a. Transparent, odorless, colorless
pearly scales having a smooth feel
b. Six sided triclinic crystals
c. White odorless bulky powder
Test for Identity:
a. Turmeric paper turns bownish-red
b. Burns with a gree-bordered flame
Pharmcology:
a. Low antseptic property
b. Toxic when taken internally
c. Toxic when applied to denuded areas
Principal symptoms: depression of the
circulation, vomiting and diarhhea
followed by shock and coma
 Associated with scarlatiniform rash giving
the appearance of a “boiled lobster”
Preparations:
a. Boric acid sol’n –Boracic acid
use as eye wash at 3.5% sol’n
b. Boric acid ointment - Borofax iontment
c. Boroglycerine Glycerite – suppository
base
2. Hydroiodic acid
- a colorless gas with a penetrating odor
Pharmacologic action:
- same with Lugols sol’n, it has systemic
effect becuase the iodine is conveted to
iodide in the GIT
 Iodides are utilized rather than the free
I2, once absorbed distribute itself
uniformly in the extracellular fluid
Iodide in the body is a source of I2 for the
synthesis of triiodothyronine and thyroxin
 The daily requirement of I2 is 200 mcg
 Lack of sufficient I2 in the diet results in:
a. Enlarge ment of the thyroid gland
b. Simple or colloidal goiter
 I2 in the diet may be insured by the use
of iodized salt which contains 0.01% KI




Lack of sufficient I2 in the diet may result
to: enlagrement of the thyroid gland and
simple or colloidal goiter
I2 may be supplied using iodized table
salt contg 0.01% KI
I2 is an essential component of the
thyroid hormone
- goitrous gland has lesser iodine and
amino acid content than normal glands
Thyrotropine – is the hormone excreted by
the anterior pituitary gland
- has bearing on the conversion of I2 to
the iodinated amino acids
- controls the release of thyroid
hormone
to the circulation, its absence none is
released
 I2
is an essential constituent of the
thyroid hormone being present in Mino
acids, thyroxin and triiodothyronine
 In comparing goitrous gland with normal
glands, there is lesser I2 and amino acid
content in the former
Therapeutic uses of Iodides:
a. Prevention of colloidal goiter
b. Ameliorating agent in hyperthyroidism
c. Fibrolytic agent in syphylis, leprosy,
sporotrichosis, blastomycosis and
actinomycosis
d. Expectorant
e. Alternative
 I2 therapy in hyperthyroidism, results to:
a. Drop in metabolic level (6 mg dosage)
b. Involution of the gland
 As expectorant, have been used in
asthma, chronic and acute bronchitis
As alternative, in excess of a ceratin level
in the body may bring certain irritative
phenomena known as “iodism” which is
manifested by rashes, headache,
conjunctivitis, laryngitis, and the like
Contraindication to I2 therapy:
a. Acne
b. Tubercolosis, which flare up even in
dormant cases

3. Hyrochloric Acid
 Occurs in active volcanoes
 Pure gastric juice contains from 0.40.5% of free HCl
- this conc does not persist in any lenght
of time since the acid is neutrlized by the
saliva, mucus, and the return flow of the
content of the duodenum
HCl is necessary to the principal digestive
function of the gastric juice, its action is
upon protein
 Sodum chloride is the source of all
commercial HCl
 HCl is a colorless gas having an acrid
irritating odor and acid taste
 It is very soluble in water and conducts
electricity

Pharmacologic action of Chloride ion:
- together with Na ions is necessary for
the osmotic function which they perform
 The exracellualr fluid contains about
0.175 of dissociated Na ions
Acidosis- caused by an excess of the
chloride ion in the body
Achlorhydria – lack of HCl in the gastric
juice
4. Phosphoric acid
 A clear, colorless , and odorless sol’n
 Phosphorite (calcium phosphate) –
“phosphate rock”, is the largest source
of phosphates for fertilizer
 Phosphates are found in soil and are
essential in the dev’t of fruits and seeds
 Metaphosphoric acid constitutes the
‘glacial phosphoric acid’ of commerce
Pharmacolgic Action of phosphate ion:
1. Acts as buffer systems for maintaining
acid-base balance
2. Integral part in the metabolism of
carbohydrates
3. In combination with calcium to form
calcium phosphate for bone formation
4. Regulates calcium metabolism and
calcium level in the blood
5. Plays a role in the regulation of body
pH because it guards the alkali reserve
 When blood calcium is high, the
phosphate is low
 There is a deficiency of calcium in
connection with leg cramps occuring in
pregnant women
 Phosphates are best absorbed from an
acid condition in the bowel
Alkaline condition an dconditions with
excess calcium in the intestine will retard
the absorption of phosphate
 The admin of substantial amounts of
sodium biphosphate will result to acid
urine
Uses of phosphoric acid:
a. Aids in the formation of peptones
b. Treatment of lead posoning

- since it lowers the pH of the blood; it
promotes decalfication of the bones and
the associated excretion of lead from the
bones at the same time
5. Nitric acid
 Also known as “eau forte” (strong water)
 It exists to a slight extent in some waters,
the air after a thunderstorm, and in the
humus of the soil
Ammonia results from decomposiiton of
vegetable and animal matter
 Bacteria oxidizes ammonia to nitric acid
and reacts with the constituents of the
soil to form nitrates
 An azeotropic mixture with water is
formed, only up to 68% acid is produced
 It is exceedingly hygroscopic and
corrosive

Acts on subs high in protein and stain
them yellow, producing a nitro cmpd
known as xanthoprotein
Pharmacology of the nitrate ion:
1. It has no specific action in the body
2. Potassium nitrate is a neutral salt but is
the most potent diuretic of all the salts
it acts by upsetting th eionic balance of
the blood and tissue fluids

6. Sulfuric Acid
 Is a non-volatile acid commonly known as
“oil of vitriol”
 Colorless, odorless liquid of oily
conssitency and when strongly heated
gives off dense, white fumes of SO3
 A viscous liquid called “oleum” also
known as Nordhausen acid, a fuming
sulfuric acid obtained by dissolving SO3
with H2SO4
Pharmacology of the Sufate ion:
1. Sulfates are not absorbed from the GIT,
oral administration does not have a
systemic effect
2. The administration in hypertonic sol’n
draws water into the lumen and provokes
the intestinal contents to peristalsis with
consequent movement of the vowel, being
a saline cathartic
3. Injection of sulfates, sod sulfate, brings
about diuresis due to the impermeability
of the renal tubule cells to the sulfate ion.
This keeps the sulfate in the tubule and
preserve it osmotic action which
diminishes the re-absorption of water thus
promotes diuresis