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By M. Irhabar. Nyack College.

On the other hand safe 0.25mcg rocaltrol, hypocalcaemia can nullify the effects of digoxin in humans; thus discount rocaltrol 0.25mcg fast delivery, digoxin may be ineffective until serum calcium is restored to normal purchase 0.25mcg rocaltrol visa. Use in Thyroid Disorders and Hypermetabolic States Hypothyroidism may reduce the requirements for digoxin. Heart failure and/or atrial arrhythmias resulting from hypermetabolic or hyperdynamic states (e. Atrial arrhythmias associated with hypermetabolic states are particularly resistant to digoxin treatment. Laboratory Tests: Digoxin toxicity may develop in the critically ill, particularly if the patient has renal impairment. Calcium, particularly if administered rapidly by the intravenous route, may produce serious arrhythmias in digitalized patients. Quinidine, verapamil, amiodarone, propafenone, indomethacin, itraconazole, alprazolam, and spironolactone raise the serum digoxin concentration due to a reduction in clearance and/or in volume of distribution of the drug, with the implication that digitalis intoxication may result. Erythromycin and clarithromycin (and possibly other macrolide antibiotics) and tetracycline may increase digoxin absorption in patients who inactivate digoxin by bacterial metabolism in the lower intestine, so that digitalis intoxication may result. Rifampin may decrease serum digoxin concentration, especially in patients with renal dysfunction, by increasing the non-renal clearance of digoxin. Rather, the earliest and most frequent manifestation of excessive dosing with digoxin in infants and children is the appearance of cardiac arrhythmias, including sinus bradycardia. The most common are conduction disturbances or supraventricular tachyarrhythmias, such as atrial tachycardia (with or without block) and junctional (nodal) tachycardia. Sinus bradycardia may be a sign of impending digoxin intoxication, especially in infants, even in the absence of first-degree heart block. Any arrhythmia or alteration in cardiac conduction that develops in a child taking digoxin should be assumed to be caused by digoxin, until further evaluation proves otherwise. Immediate release tablets are the only formulation that can be administered via a nasogastric tube. Note: dosage errors with diltiazem are common due to the variety of formulations that exist. Sick sinus syndrome except in the presence of a functioning ventricular pacemaker 2. Acute Hepatic Injury Mild elevations of transaminases with and without concomitant elevation in alkaline phosphatase and bilirubin have been observed in clinical studies. Such elevations were usually transient and frequently resolved even with continued diltiazem treatment. Concomitant administration of diltiazem with carbamazepine has been reported to result in elevated serum levels of carbamazepine (40-72% increase), resulting in toxicity in some cases. A pharmacokinetic interaction between diltiazem and cyclosporin has been observed during studies involving renal and cardiac transplant patients. In renal and cardiac transplant recipients, a reduction of cyclosporin dose ranging from 15-48% was necessary to maintain cyclosporin trough concentrations similar to those seen prior to the addition of diltiazem. If these agents are to be administered concurrently, cyclosporin concentrations should be monitored, especially when diltiazem therapy is initiated, adjusted, or discontinued. Coadministration of rifampin with diltiazem lowered the diltiazem plasma concentrations to undetectable levels. Coadministration of diltiazem with rifampin should be avoided when possible, and alternative therapy considered. Nervous System: Headache, abnormal dreams, amnesia, depression, gait abnormality, hallucinations, insomnia, nervousness, paraesthesia, personality change, somnolence, tinnitus, tremor. Chest pain may be aggravated in patients with underlying coronary artery disease who are receiving dipyridamole. Hepatic Insufficiency: Elevations of hepatic enzymes and hepatic failure have been reported in association with dipyridamole administration. Cholinesterase Inhibitors: Dipyridamole may counteract the anticholinesterase effect of cholinesterase inhibitors, thereby potentially aggravating myasthenia gravis. Dermatological System: Rash, urticaria Haematological System: Thrombocytopaenia Dipyridamole! Ectopic Activity: Dobutamine may precipitate or exacerbate ventricular ectopic activity, but only rarely causes ventricular tachycardia. The vasodilation in these vascular beds is accompanied by increased glomerular filtration rate, renal blood flow, sodium excretion and urine flow. An increase in urinary output produced by dopamine is usually not associated with a decrease in osmolality of the urine. There is little, if any, stimulation of the beta2-adrenoceptors (peripheral vasodilation). Blood flow to the peripheral vascular beds may decrease while mesenteric flow increases due to increased cardiac output. Total peripheral resistance (alpha effects) at low and intermediate doses is usually unchanged. At higher rates of infusion (10-20 mcg/kg/min), there is some effect on alpha- adrenoceptors, with consequent vasoconstrictor effects and a rise in blood pressure. The vasoconstrictor effects are first seen in the skeletal muscle vascular beds, but with increasing doses, they are also evident in the renal and mesenteric vessels. At very high rates of infusion (above 20 mcg/kg/min), stimulation of alpha-adrenoceptors predominates and vasoconstriction may compromise the circulation of the limbs and override the dopaminergic effects of dopamine, reversing renal dilation and natriuresis. The overall prevalence of sulphite sensitivity in the general population is unknown and probably low. Sulphite sensitivity is seen more frequently in asthmatic than in non-asthmatic people. At lower infusion rates, if hypotension occurs, the infusion rate should be rapidly increased until adequate blood pressure is obtained. If hypotension persists, dopamine should be discontinued and a more potent vasoconstrictor agent such as noradrenaline should be added. Concurrent administration of low-dose dopamine and diuretic agents may produce an additive or potentiating effect on urine flow. It is suggested that in patients receiving dopamine, alternatives to phenytoin should be considered if anticonvulsant therapy is needed. Other: Gangrene of the extremities has occurred when high doses were administered for prolonged periods or in patients with occlusive vascular disease receiving low doses of dopamine. Priapism: Doxazosin may cause priapism; if this occurs, urgent urological advice is required. Congestive heart failure or left ventricular dysfunction after myocardial infarction 3. Hypersensitivity to enalapril or any other angiotensin-converting enzyme inhibitor (e. If angioedema involves the tongue, glottis or larynx, airway obstruction may occur and be fatal. Swelling confined to the face, mucous membranes of the mouth, lips and extremities has usually resolved with discontinuation of enalapril; some cases required medical therapy. These patients presented with abdominal pain (with or without nausea or vomiting); in some cases there was no prior history of facial angioedema and C-1 esterase levels were normal. Hypotension in Heart Failure Patients Caution should be observed when initiating therapy in patients with heart failure.

It is cheap rocaltrol 0.25 mcg with amex, however purchase discount rocaltrol line, pertinent to mention here that the application of both emperical ratio method and base- line method help in eliminating to a great extent the errors caused due to changes in source intensity and adjustment of the optical system generic 0.25 mcg rocaltrol. Determination of the Absorption Spectrum of a Solid Compound (or a Pharmaceu- tical Substance) The determination of the absorption spectrum of a solid pharmaceutical substance is invariably ac- complished by any one of the two following techniques namely : (a) Mull Technique, and (b) Potassium Bromide Disc Technique. Mull Technique Procedure : Take about 15-20 mg of sample in a previously cleaned small agate mortar and powder it thoroughly (about 200 mesh). Add to it 2 drops of purified paraffin (commonly known as Nujol) or any other suitable mulling liquid and continue the trituration until a very smooth paste of uniform consistency is achieved. Now, transfer the slurry to a sodium chloride window, placing it carefully into the cavity made by the spacer. With the help of a clean piece of tissue-paper wipe out the excess paste that has squeezed out from the cell windows. Salient Features : The salient features of Mull Technique are as follows : (i) Particle size of the sample has got to be reduced below 200 mesh or 3 µm so as to avoid scattering of radiation thereby causing poor absorption spectrum. Now, carefully place the sample mixture into the pressing chamber of the mould in such a manner that it is held between the polished surfaces of the bottom and top pressing dies. Subsequently, attach the chamber to the vacuum line and switch-on the vacuum pump ; initially applying a slight negative pressure so as to compact the powder and then gradually increasing it to ≤ 15 mm Hg for 30 seconds. Finally, enhance the pressing force to 100,000 lb/in2 or 10-12 tons/in2 for a period of 1-2 minutes. Now, remove the window from the mould and keep it in position onto the sample holder. Consequently, the solid is powdered, pressed into a disc in the normal procedure and ultimately the absorption spectrum of the trapped substance is studied, (iii) It enjoys the advantage of producing spectra absolutely free from any solvent peaks (unlike Mull Technique) and hence it is employed extensively in routine analysis. In order to overcome this tedious process of measuring disc thickness carefully the use of an internal standard has been introduced. In usual prac- tice, it must be preground, dried and subsequently reground, and used at a concentration of 0. Now, the ratio of the thiocyanate absorption at 2125 cm–1 to a selected band absorption of the analyte is plotted against the percent concentration of the sample. Finally, its absorbance ratio is determined and the concentration (of unknown sample) is read off directly from the standard calibration curve. Calibration of Infrared Spectrophotometers The wavelength (or wave number) scale calibration of infrared spectrophotometers is usually carried out with the aid of a strip of polystyrene film fixed on a frame. It consists of several sharp absorption bands, the wavelengths of which are known accurately and precisely. Grind the mixture thoroughly, spread it uniformly in a suitable die and compress under vacuum at a pressure of about 10 t in–2. Precautions : The following precautions may be observed carefully : (i) Several factors e. Determination of Aspirin, Phenacetin and Caffeine in Tablets Theory : The quantitation is solely based on the intensities of the carbonyl bands at 1764, 1511 and 1665 cm–1 for aspirin, phenacetin and caffeine respectively. Determination of Meprobamate in Tablets Maynard (1960) carried out the analysis of meprobamate by dissolving it in chloroform (spectroscopic O  grade) and subsequently determining the intensity of the amide carbonyl band at 1582 cm–1. Later ( C) Shearken (1968) adopted a modified method of assay by using chloroform as an extracting medium, but instead of the carbonyl band measured the N—H stretching band at 3436 cm–1. This aspect is duly expatiated with the aid of the following typical examples, namely : 22. Theory : It is an established fact that cis- and trans-substituted double bonds have slightly different absorption bands in the region of 13 µm. Besides, the pharmacological actions of many compounds are invariably dependent on the shape of molecules and hence, usually play a very significant role. Therefore, if both cis- and trans-isomers are pro- duced in the course of a particular synthesis it may be absolutely necessary to incorporate in the product profile a specific test for the relative proportions of one to the other. This type of ‘control measure’ strictly conforms the uniformity of composition in the bulk-drug industry and ensures a check on the batch-to-batch variation. In the alkaline medium the base is liberated which is extracted successively with 3 portions of solvent ether (10 ml each). Finally, repeat the assay with a 1 : 1 mixture (75 mg) of cis and trans-clomiphene citrates and also with clomiphene citrate (75 mg) as such. It may be further expatiated due to the fact that a functional group which often results in many specific and characteristic absorption bands can be identified more precisely and definitely than a function which produces only one characteristic absorption band. Thus, pharmaceutical substances that exhibit the same infrared spectra may be inferred as identical. These instruments have the advantage of storing in their computer-memory-banks of sizable number of digitalized information obtained from the infrared spectra of standard compounds. Now, with the flick of a keyboard button the spectrum of an unknown compound, previously fed to the same digital storage bank, may be conveniently compared with the stand- ards and finally to get at the identical infrared absorptions to the unknown. However, following different aspects must be taken into consideration while interpreting the spectrum : (a) In usual practice, the absence of a strong group absorption definitely indicates the absence of that group in the molecule, based on the assumption that no other factors are influencing which might shift the absorption band to the other regionse. In other words, intramolecular or intermolecular changes caused due to the hydrogen bonding help in shifting the expected absorption band either to the higher region or to the lower region. For instance : the clear absence of a sharp and strong absorption band in the region 1850-1640 cm–1 (or 5. It frequently consists of a relatively large number of bands the origin of which is neither located nor determined so easily. Broadly speaking, the ‘fingerprint region’ helps in the identification of unknown pharmaceutical substances with the aid of reference samples and comparing the two spectra by superimposing them on one another. For a simple diatomic molecule X-Y the sole vibration which may take place in a periodic stretch- ing along the X-Y band. Thus, the stretching vibrations may be visualized as the oscillations of two entities connected by a spring and the same mathematical treatment, known as Hooke’s Law, holds good to a first approximation. Hence, for stretching of the band X-Y, the vibrational fre- quency (cm–1) may be expressed by the following equation : ν = 1302 k/... In addition to the above cited typical instances the hydrogen bonding can also be studied at length by subsequent replacement of proton by deuterium. What are the two commonly used techniques invariably employed for the determination of ‘absorption spec- trum’ of a solid ‘drug’. Consequent to the magnetic properties of nuclei arising from the axial spin, the emerging radio- frequency gets absorbed in a magnetic field. Evidently, the location of peaks indicate the chemical nature of the nucleus, whereas the multiplets provide information regarding the spatial positions of the neighbouring nuclei. Besides, it is invariably utilized as a specific method of assay for the individual constituents of a mixture. A few typical examples of drug assays will be dealt separately at the end of this chapter to justify its efficacy and usefulness. It does so because it evidently possesses an electrical charge as well as a mechanical spin.

If the patient passes through this stage into a deeper stage of narcosis there may be a transient period of talkativeness as he recovers from the sedation or anesthesia purchase rocaltrol discount. For certain personality types buy generic rocaltrol 0.25 mcg on line, some drugs lower conscious ego control generic rocaltrol 0.25 mcg line, thereby facilitating recall of repressed material and increasing the difficulty of withholding available information. The ideal drug for an interrogator would be one which not only accomplishes this feat, but does so without interfering with integrative capacities and intellectual functioning. Because of the uncertainty of the truth or falsity of statements obtained under circumstances of reduced ego control, and because certain drugs may give rise to psychotic manifestations such as hallucinations, illusions, delusions, or disorientation, the verbal material obtained cannot always be considered valid. Such data is not accepted in a court of justice and the information so obtained is not considered wholly accurate by the medical profession. Jean Rolin (112) has written a book entitled Police Drugs in which he inveighs strongly against the use of drugs for medico-legal purposes. His argument is in part moral, but it is also based on the grounds that there is uncertainty as to the truth of revelations obtained by such means. In summarizing the viewpoint of the medical profession on narcoanalysis, he says: Narcoanalysis is not a sure method of bringing out the truth and nothing but the truth. Any confession made is not necessarily true; and if no confession is made this does not necessarily prove that the patient has not committed the crime with which he may be charged. Does this mean that narcoanalysis has no importance at all from the angle of the administration of justice? The answer to this question is again in the negative, because in many cases the confession is true and often facts are brought out which are very helpful to the public prosecutor in proving his case. It seems fair to say that in the present stage of development narcoanalysis can be of great help in finding the truth. But it is also a dangerous means of investigation as the right interpretation of statements made depends largely on the skill of the analyst. The first study is only of borderline relevance and involves the use of intravenous barbiturates as an aid in the differential diagnosis between conversion hysteria and malingering. The author (104) claimed that the use of intravenous sodium amytal was found to be helpful in detecting (and treating) individuals who were suspected of consciously distorting and feigning disability. He found such individuals to be negativistic, sullen, and nonproductive at first under amytal but prone to reveal the fact of and causes for their malingering as the interview proceeded. It was common in his experience to turn up a neurotic or psychotic basis for the malingering. Redlich, Ravitz, and Dession (109) asked a total of nine university students and professional persons to relate some true shame- or guiltproducing life incident. Then the subjects were asked to invent a "cover story" to be told to another examiner who interrogated them after the intravenous injection of amobarbital, 0. In six of the subjects, the "cover story" was given during the amytal interrogation, in one it was mixed with the true story, and in two the true story was given. In nearly all subjects, the "cover story" contained elements of the guilt involved in the true story. An additional finding of interest was that the more normal, well-integrated individuais could lie better than the guilt-ridden, neurotic subjects. Gerson and Victoroff (53) used amytal interviews on neuropsychiatric patients who had charges against them at Tilton General Hospital, Fort Dix, New Jersey. The patients were told that none of the material from the interviews would be used in the prosecution of charges against them, since it was considered a breach of medical ethics and because the material, derived with the full knowledge and consert of the patient, could not have been presented in court without violating the Twenty-fourth Article of War and the Bill of Rights of the Constitution of the United States. The researchers first gained the confidence of the patients by discussing their life history. They were not informed that amytal would be used until a few minutes before narcoanalysis was undertaken. During the follow-up interview, nine patients admitted the validity of their confessions and eight repudiated their confessions. Gerson and Victoroff examined the following factors interfering with the completeness and authenticity of the confessions: (a) inept questioning, (b) tendency of the patient to perseverate on unrelated topics, (c) mumbled, thick, inaudible speech and paralogia, (d) fantasies, (e) contradictory but apparently truthful evidence, and (f) poor rapport between doctor and patient. These experimenters concluded from their study that under sodium amytal subjects could sometimes lie and that their reasoning powers were sometimes present, although much distorted. Although they found amytal narcoanalysis successful for the revelation of deception, they felt that the validity of the information -115- garnered by this method was not so decisive that it could be admissible in court without further investigation and substantiation. Thiopental, atropine, amphetamine, methamphetamine, sodium amobarbital, ethyl alcohol, scopolamine hydrobromide, pentobarbital sodium, morphine, caffeine sodium benzoate, and mescaline sulfate were given singly and in combination. The subjects were motivated by their desire for monetary compensation, their perceived importance of the experiment, and pride in their integrity and "will power. To check possible forgetting, the subject was asked to produce the withheld information at the end of the experiment, and this was verified against the written version. The drugs and combinations of drugs used in these experiments were given in such large amounts that they produced grossly abnormal states of mind. At various times, subjects became semicomatose, mildly delirious, panicky, markedly loquacious, euphoric or underwent transient dissociative reactions; yet, curiously, at no time was there sufficient ego impairment that they were unable to identify the significance of questions about the suppressed information and avoid answering them in response to direct questioning. As long as they remained in auditory contact with the interrogator, they consistently refused to reveal the suppressed items. Similarly, none of them revealed the suppressed items of amnestic data in response to specific questioning. However, on two occasions the names of close relatives being used as suppressed information were revealed, apparently as slips of the tongue, in the course of spontaneous, dissociative rambling while severely intoxicated with scopolamine and thiopental in combination. The findings with the "cover story" technique were essentially those of Redlich et al. Under thiopental narcosis, two subjects produced significant variations in the cover story which betrayed the content of the true story. However, the remaining subjects, if they were able to talk at all coherently, reproduced the cover stories with remarkable fidelity to the original version. In evaluating the considerable ego-integrity maintained by these subjects, it is important to consider that they may have felt relatively secure in a protected experimental situation, in the hands of a responsible experimenter and physician. Furthermore, a lack of crucial information from a subject under a drug does not mean that the subject has no information. An interrogator would have to evaluate many other factors — the personality of the subject, the milieu, other sources of evidence, etc. Specific Effects of Drugs on Verbal Behavior, Particularly Drugs Potentially Applicable to Interrogation Procedures After looking at these efforts to elicit information with a variety of drugs, it may be well to consider each psychopharmacologic agent in turn, for its possible applicability to the interrogation situation. Barbiturate Sedatives and Calmatives The major share of studies on the use of drugs in interviewing procedures involves the barbiturates: amobarbital, secobarbital, and pentothal. These drugs have been found useful in treating the acute war neuroses (58, 116, 117), and in civilian practice (23, 32, 106). In psychiatric practice, the purpose of these drugs is to effect a violent emotional response which may have cathartic value for the patient.

Filter the precipitate of the resulting complex through a prepared Gooch crucible buy cheap rocaltrol on line, previously dried to constant weight at 105°C generic 0.25 mcg rocaltrol free shipping. Wash the precipitate with ethanol followed by acetone and carbon tetrachloride buy rocaltrol 0.25 mcg on-line, allow to drain as completely as possible, and dry to a constant weight at 105°C. Theory : The gravimetric assay of thiamine hydrochloride is based upon the precipitation of it as thiamine silicotungstate with silicotungstic acid in a slightly acidic medium. For a reasonably precise and accurate determination the precipitating reagent must contain <| 1. Interestingly, the thiamine silicotungstate complex possesses more or less a constant composition. Transfer the precipitate quantitatively and wash it thoroughly with four quantities each of 5. Simultaneously, determine the loss in weight on drying a separate portion of the sample at 105°C. Theory : Gravimetric analysis of proguanil hydrochloride involves the precipitation of the proguanil- cupric complex that results on the addition of ammoniacal cupric chloride solution to a solution of proguanil hydrochloride. Chill the solution below 10°C in an ice-bath and then add ammoniacal-cupric-chloride solution with continuous stirring till the resulting solution attains a permanent deep-colour. Allow the solution to stand for 90 minutes to complete the complexation and then filter through a No. Simultaneously, find out the loss in weight on drying with a separate portion of the sample at 105°C and incorporate this in the calculation. Benzethonium Chloride Theory : In general, quaternary nitrogen containing compounds like—choline chloride, acetylpyridinium chloride, benzethonium chloride, and bethanechol chloride readily form insoluble salts quantitatively with tetraphenyl boron and this puts forward the basis for the gravimetric assay of the above cited pharmaceutical substances. Allow to cool and dilute to 100 ml with ethanol 96%] : 50 ml ; sodium tetraphenyl borate solution (1% w/v in chloroform) : 50 ml ; sintered-glass crucible No : 4. Cool to ambient temperature and add suffcient bromophenol blue solution gradually till the solution yields a blue Chloroform-soluble complex. Now, add sodium tetraphenyl borate solution in small lots at intervals with constant stirring until the complete precipitation of insoluble benzethonium tetraphenyl borate complex takes place. Allow the solution to stand for 60 minutes to complete the complexation and subsequently filter through a No. Transfer the precipitate quantitatively into the crucible and wash the precipitate with cold chloroform. Cognate Assays Quite a few official pharmaceutical substances and their respective dosage forms can be assayed gravimetrically after conversion to their corresponding derivatives or substitution products. How does the ‘Law of Mass Action and Reversible Reactions’ help in accomplishing the gravimetric analysis? How would you assay the following ‘drugs’ gravimetrically : (i) Sodium chloride (ii) Potassium alum (iii) Barium sulphate (iv) Piperazine phosphate. Gravimetric analysis may be accomplished by one of the following means and ways : (a) Substances assayed after conversion to Free Acid, (b) Substances assayed after conversion to Free Base, (c) Substances assayed after conversion to Free Compound, and (d) Substances assayed after conversion to Derivatives. In usual practice, data are generated as a result of continuously re- corded curves that may be considered as ‘thermal spectra’. These thermal spectra also termed as‘thermograms, often characterize a single or multicomponent system in terms of : (a) temperature dependencies of its thermodynamic properties, and (b) physicochemical reaction kinetics. All the above mentioned techniques shall be discussed briefly with specific reference to their theory, instrumentation, methodology and applications wherever necessary. Static Thermogravimetric Analysis In this particular instance the sample under analysis is maintained at a constant temperature for a period of time during which any changes in weight are observed carefully. Dynamic Thermogravimetric Analysis In dynamic thermogravimetric analysis a sample is subjected to conditions of predetermined, carefully controlled continuous increase in temperature that is invariably found to be linear with time. Balance Automatic gas switching Furnace First gas Sample Second gas Flow meter Cooling fan Needle Pure gas valve outlet Stopper Figure 11. Balances They are usually of two types : (a) Null-point Type : It makes use of an appropriate sensing-element which aptly detects any slightest deviation of the balance beam and provides the application of a restoring force, directly propor- tional to the change in weight, thereby returning the beam to its original null-point. The restoring- force is subsequently recorded either directly or with the aid of a transducer. Furnace The furnace must be designed in such a fashion so as to incorporate an appropriate smooth input thereby maintaining either a fixed temperature or a predetermined linear-heating programme (e. The temperature control of the furnace is satisfactorily achieved via a thermocouple mounted very close to the furnace-winding. The maximum operational temperature may be obtained by using different thermocouples as indicated below : S. Graphite-Tube Furnace* > 1500 *Control and measurement of temperatures are critical and problematic. Recorder The recording device must be such so as to : (i) record both temperature and weight continuously, and (ii) make a definite periodic record of the time. The successive plateaus correspond to the anhydrous oxalate (100-250°C), calcium carbonate (400-500°C), and finally calcium oxide (700-850°C). In other words, these plateaus on the decomposition curve designate two vital aspects, namely : (a) clear indication of constant weight, and (b) stable phases within a specified temperature interval. The chemical reactions involved may be summarized as follows : 100-250°C 400-500°C 700-850°C CaC2O4. H2O (20 mg) 8 CaO 6 750° 850° Start 200 400 600 800 1000 Temperature (°C) Figure 11. Stage 1 : The water of hydration (or crystallization) from calcium oxalate monohydrate is lost which corresponds to 2. In a situation whereby an inert material is present along with a pure substance, from the generated thermogram the composition of the mixture may be derived from the percentage weight variation which takes place relative to the percentage weight variation observed with the pure compound (A), by employing the following expression : % wt. It has been observed that in humidified air at low heating rates, hydrates usually give rise to good plateaus. In this specific instance the sample is either heated under vacuum or in an inert atmosphere (of N2). A typical commercial differential thermal analyzer is schematically illustrated in Figure 11. The said two thermocouples help in measuring the difference in temperature between a sample S and an absolutely inert reference substance R, as both are subjected to heating in a ceramic or metal block inside a furnace being operated by a temperature programmer and controller. An almost constant heating rate is usually achieved by using a motor-driven variable auto transformer. Both heating rates and cooling rates may be conveniently adjusted continuously : (i) From 0°-30°C/minute by some instruments, and (ii) From a choice of several commonly employed heating rates viz. A few of these aspects vital aspects are : • Pretreatment of the specimen, • Particle size and packing of the specimen, • Dilution of the specimen, • Nature of the inert diluent, • Crystalline substances must be powdered, and sieved through 100-mesh sieve, • For colloidal particles (e. In usual practice, the temperature of solution is plotted against the volume of titrant. As the dielectric constant of a solvent exerts little effect on the thermometric titrations, the latter may be employed effectively in most non-aqueous media. To minimise heat transfer losses from the solution by its immediate surroundings, the thermometric titrations are usually carried out in an isolated-beaker tightly closed with a stopper having provision for a burette-tip, a motorized-glass stirrer, and a temperature-monitoring arrangement. Procedure : (a) Introduce the titrant from a burette that is duly mounted in a thermostated-water-jacket to maintain the temperature of the titrant within ± 0. The values of the circuit component listed are for a thermister having an approximate resistance of 2 KΩ and a sensitivity of –0.

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