Acid neutralisation

The ethereal solution of crude quinidine and cinchonidine, obtained as described under cinchonine, is shaken with dilute hydrochloric acid, the excess acid neutralised with ammonia and sodium potassium tartrate added. The base is recovered from the precipitated tartrate by dissolving the latter in dilute acid and pouring the filtered solution in a thin stream, slowly and with constant stirring, into excess of ammonia solution. The crude alkaloid is converted into the neutral sulphate, and this recrystallised... 

Either the Mohr titration or the adsorption indicator method may be used for the determination of chlorides in neutral solution by titration with standard 0.1M silver nitrate. If the solution is acid, neutralisation may be effected with chloride-free calcium carbonate, sodium tetraborate, or sodium hydrogencarbonate. Mineral acid may also be removed by neutralising most ofthe acid with ammonia solution and then adding an excess of ammonium acetate. Titration of the neutral solution, prepared with calcium carbonate, by the adsorption indicator method is rendered easier by the addition of 5 mL of 2 per cent dextrin solution this offsets the coagulating effect of the calcium ion. If the solution is basic, it may be neutralised with chloride-free nitric acid, using phenolphthalein as indicator. 

Obviously, use of such databases often fails in case of interaction between additives. As an example we mention additive/antistat interaction in PP, as observed by Dieckmann et al. [166], In this case analysis and performance data demonstrate chemical interaction between glycerol esters and acid neutralisers. This phenomenon is pronounced when the additive is a strong base, like synthetic hydrotalcite, or a metal carboxylate. Similar problems may arise after ageing of a polymer. A common request in a technical support analytical laboratory is to analyse the additives in a sample that has prematurely failed in an exposure test, when at best an unexposed control sample is available. Under some circumstances, heat or light exposure may have transformed the additive into other products. Reaction product identification then usually requires a general library of their spectroscopic or mass spectrometric profiles. For example, Bell et al. [167] have focused attention on the degradation of light stabilisers and antioxidants... 

Acid scavengers - Acid neutralisers - Antiacids Activators... 

Net acidity of tailings was determined using a modification of the procedure described by Ahern et al. (2000). Potential sulfidic acidity was determined from XRF S determinations. Net acidity was taken as the sum of the potential sulfidic acidity and titratable actual acidity, less the acid neutralisation capacity. 

Table 1. Acid neutralising or inhibiting regimes in oesophageal reflux disease...

Mining wastes and overburden. Estonian kukersite oil shales occur in limestone strata (Schmidt 1858, 1881), yielding a carbonate-rich spoil with significant potential for acid neutralisation. Other oil shales, for example, the siliceous Estonian Dictyo-nema shales, which contain only traces of carbonate compared with the kukersites, are associated with sulphides, such as pyrite, and may thus generate acidic leachate due to pyrite oxidation (Puura Pihlak 1998 Puura et al. 1999). 

Giampaoi.o, C. Lo Mastro, S. 2002. Acid neutralisation capacity and hydration behaviour of incineration bottom ash-Portland cement mixtures. Cement and Concrete Research, 32, 769-775. 

From Alcohol.—To 32 gms. potassium carbonate dissolved in 80 gms. water 16 gms. 95% alcohol are added, and the solution heated to 70°. 32 gms. powdered iodine are added gradually with stirring. Iodoform gradually separates out, and when the solution has become completely decolorised, is filtered off, washed with water, and dried at ordinary temperature. A further yield is obtained by adding 2—3 gms. potassium bichromate and 16—24 gms. cone, hydrochloric acid, neutralising and adding 32 gms. potassium carbonate, 16 gms. 95% alcohol and 6 gms. iodine, and carrying out as before. 

Examine in a polarimeter and note dextrorotation. Then heat with a little dilute sulphuric acid, neutralise carefully, and again examine in polarimeter. Note laevorotation. Fructose is more lsevorotatory than glucose is dextrorotatory. 

From this equation it can be seen that 1 mole of hydrochloric acid neutralises 1 mole of sodium hydroxide. 

Alkalinity is a measure of the acid-neutralising capacity of water and is usually determined by titration against sulphuric acid to the endpoint of the acid—base reaction. In groundwaters, the carbonate species predominate and an endpoint of... 

Volumetric Methods.—Nickel may be conveniently estimated volu-metrically in the absence of cobalt, copper, silver, gold, and the platinum metals by means of potassium cyanide.4 The solution containing the nickel is, if acid, neutralised with ammonia and some ammonium sulphate is added to render the indicator more sensitive. A little ammonia is now added, and a few drops of potassium iodide and silver nitrate. The solution becomes turbid in consequence of the precipitation of silver iodide. The liquid is now titrated with potassium cyanide solution until the turbidity just disappears. The reaction consists in converting the nickel salt into the double cyanide, Ni(CN)a.2KCN, after which any excess of potassium cyanide attacks the silver iodide, yielding the soluble double cyanide, AgCN.KCN. The disappearance of the turbidity therefore indicates the complete conversion of the nickel salt. A slight correction is necessary for the silver introduced. 

Vfhite crystalline powder, 99 to 100% active. Sequesters metal ions in aqueous solutions over a fairly wide pH range rendering them soluble in conditions which would normally lead to precipitation of their metallic salts. The adverse effects of small concentrations of metal ions such as calcium, magnesium, iron and copper are thus successfully eliminated. Tetralon acid neutralised with a suitable base is used where maximum purity or freedom from sodium ions is desired. 

Ammonium Chromithiocyanate, (NH4)3[Cr(SCN)6].4H20, is formed by dissolving freshly precipitated hydroxide in ammonium-thiocyanate solution, or by reducing ammonium dichromate wth alcohol and sulphuric acid, neutralising the solution with ammonia, adding ammonium thiocyanate, and boiling for a short time. ... 

Evans C. D., Harriman R., Monteith D. T., and Jenkins A. (2001a) Assessing the suitability of acid neutralising capacity as a measure of long-term trends in acid waters based on two parallel datasets. Water Air Soil Pollut. 130, 1541-1546. 

N sodium carbonate solution and the remaining acid neutralised with a slight excess of sodium bicarbonate. Starch solution is added and the arsenite present titrated with iodine. 

Tears have some buffering capacity so, as we noted before, the pH-partition hypothesis has to be applied with some circumspection. The acid neutralising power of the tears when 0.1 cm of a 1% solution of a dmg is instilled into the eye is approximately equivalent to 10 fjL of a 0.01 mol dm strong base. The pH for either maximum solubility (see Chapter 5) or maximum stability (see Chapter 4) of a dmg may well be below the optimum in relation to acceptability and activity. Under these conditions it is possible to use a buffer with a low buffering capacity to maintain a low pH adequate to prevent change in pH due to alkalinity of glass or carbon dioxide ingress from the air. When such drops are instilled into the eye the tears will participate in a fairly rapid remm to normal pH. 

In order to avoid this undesirable effect and to promote metal ion accumulation in the liquid phase, Ryss and Goldberg (1973) developed a special element-collector. This consists of a vessel containing a metallic electrode and a semi-permeable membrane, on one side of which is a solution of nitric acid (Fig. 2-17). The semi-permeable membrane prevents egress of the acid solution and allows ionic exchange between the element-collector and the surrounding environment. The acid neutralises the hydroxyl ions and thereby maintains the solubility of metal ions in the vicinity of the cathode. 

The label should indicate if a tablet or capsule contains one, two or three adult standard dosage forms of the drug. Liquid preparations should indicate similarly if there is one, two or three adult standard dosage forms per teaspoon of the preparation. Buffered salicylate products must have at lezist 1.9 milliequiveilent of acid neutralising capacity per adult dosage unit. 

Any acids that do form in the cylinder must be neutralised rapidly. Different overbased additives have different acid neutralisation rates and reaction rates can be increased by small additions of suitable additives. Several laboratory tests have been developed to compare neutralisation rates. Most are dependent on measuring the carbon dioxide evolved when sulphuric acid is added to candidate oils in laboratory glassware, both in the presence and absence of iron. 

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