ACIDS AND BASES

1. ACIDS AND BASES Dr. Althea R. Arenajo

2. ACIDS and BASES • 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 OH1- 2. Bronsted-Lowry Concept (protonic concept of acidity)

3. ACIDS and BASES 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

4. ACIDS and BASES • 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

5. ACIDS and BASES 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

6. ACIDS and BASES • 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

7. ACIDS and BASES 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

8. ACIDS and BASES • 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 AcidBase bromophenol blue yellow blue bromocresol green yellow blue

9. ACIDS and BASES 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

10. ACIDS and BASES • 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

11. ACIDS and BASES • 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

12. ACIDS and BASES • 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 (Braun- Knecht-heimann Co) g. Oxyphen paper(J. Einstein Co)

13. ACIDS and BASES • 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

14. ACIDS and BASES • 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

15. ACIDS and BASES • 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

16. ACIDS and BASES • 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

17. ACIDS and BASES 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

18. ACIDS and BASES 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

19. ACIDS and BASES 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

20. ACIDS and BASES 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

21. ACIDS and BASES 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

22. ACIDS and BASES • 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

23. ACIDS and BASES • 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

24. ACIDS and BASES 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

25. ACIDS and BASES • 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

26. ACIDS and BASES 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

27. ACIDS and BASES • 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: • Acne • Tubercolosis, which flare up even in dormant cases

28. ACIDS and BASES 3. Hyrochloric Acid • Occurs in active volcanoes • Pure gastric juice contains from 0.4- 0.5% 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

29. ACIDS and BASES • 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

30. ACIDS abd BASES 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

31. ACIDS and BASES 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

32. ACIDS and BASES 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

33. ACIDS and BASES 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

34. ACIDS and BASES • 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

35. ACIDS and BASES - 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

36. ACIDS and BASES • 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

37. ACIDS and BASES • Acts on subs high in protein and stain them yellow, producing a nitro cmpd known as xanthoprotein Pharmacology of the nitrate ion: • It has no specific action in the body • 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

38. ACIDS and BASES 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

39. ACIDS and BASES 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

40. ACIDS and BASES 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