Precipitation completeness

Initial precipitation Complete precipitation Initial precipitation Complete precipitation... 

Example 2. How many mL of N hydrochloric acid are required to precipitate completely 1 g of silver nitrate ... 

Using the pKa and the estimated So, the DTT procedure simulates the entire titration curve before the assay commences. Figure 6.7 shows such a titration curve of propoxyphene. The simulated curve serves as a template for the instrument to collect individual pH measurements in the course of the titration. The pH domain containing precipitation is apparent from the simulation (filled points in Fig. 6.7). Titration of the sample suspension is done in the direction of dissolution (high to low pH in Fig. 6.7), eventually well past the point of complete dissolution (pH <7.3 in Fig. 6.7). The rate of dissolution of the solid, described by the classical Noyes-Whitney expression [37], depends on a number of factors, which the instrument takes into account. For example, the instrument slows down the rate of pH data taking as the point of complete dissolution approaches, where the time needed to dissolve additional solid substantially increases (between pH 9 and 7.3 in Fig. 6.7). Only after the precipitate completely dissolves, does the instalment collect the remainder of the data rapidly (unfilled circles in Fig. 6.7). Typically, 3-10 h is required for the entire equilibrium solubility data taking. The more insoluble the... 

D. 2,3-Diamino pyridine (Note 12). In an apparatus for catalytic hydrogenation (Note 13) 56.4 g. (0.3 mole) of 2,3-diamino-5-bromopyridine suspended in 300 ml. of 4% sodium hydroxide solution is shaken with hydrogen in the presence of 1.0 g. of 5% palladized strontium carbonate (Note 14). When absorption of hydrogen is completed, the catalyst is removed by filtration, and, after saturation with potassium carbonate (about 330 g. is required), the resulting slushy mixture is extracted continuously with ether until all the precipitate completely disappears (usually about 18 hours, but this depends on the efficiency of the extraction apparatus). The ether is removed by distillation, and the residue of crude 2,3-diaminopyridine is recrystallized from benzene (about 600 ml. is required) using 3 g. of activated charcoal and filtering rapidly through a preheated Buchner funnel. The yield of 2,3-diaminopyridine, obtained as colorless needles, m.p. 115-116°, pKa 6.84, is 25.5-28.0 g. (78-86%) (Note 15). 

Chlorinity was first defined in 1902 and, hence, was affected by subsequent refinements in measurement of the atomic weight of chlorine. To make chlorinity independent of any such future changes, a new definition of chlorinity was adopted in 1937, e g., the mass of silver required to precipitate completely the halogens in 0.3285234kg of sample seawater. ... 

Preparation of Zinc Chloride Crystallohydrate. Put 5 g of granulated zinc into a 50-mI flask, pour in 12 ml of water, and add 13 ml of concentrated hydrochloric acid in small portions. When the reaction slows down, place the flask on a warm water bath and bring the reaction up to its end. Let the flask with its contents stand up to your next lesson. Filter the solution, and test it for the presence of iron(II) ions. If the reaction is positive, saturate the solution with chlorine. For what purpose Tightly close the flask containing the reaction mixture with a stopper and again let it stand up to your next lesson. Heat the flask in a water bath and introduce moist zinc oxide in small portions up to the complete separation of iron hydroxide. How can you determine that the ions of iron have precipitated completely ... 

An aqueous solution of telluric acid gives with hypophosphorous acid a colloidal solution of tellurium which is precipitated completely on boiling and can then be filtered and weighed. This method is only available if there are no other salts present which might be reduced.6... 

From 18.5g of mercuric chloride in 200ml of hot water, black mercuric sulfide is precipitated completely by hydro-... 

If the conjugate becomes insoluble, precipitate completely with 4—5 vol of ice-cold acetone at-70°C for 30 mm. Briefly warm at room temperature. Pour off the supernatant and air-dry Resuspend in saline as m Section 3 1, step 4. Alternatively, if the conjugate remains soluble, desalt the solution on a 20-mL Sephadex G25 column using ammonium hydrogen carbonate buffer, pH 7 5. Collect 2-mL fractions, and pool those of OD280 > 0.4 Store at -20°C. 

After all of the cyanuric acid has been depolymerized, anhydrous ammonia is passed directly into the ethereal solution of isocyanic acid. Precipitation is immediate, and efficient stirring is necessary to prevent clogging of the inlet tube. Because of the voluminous nature of the precipitate, completion of the neutralization is difficult to ascertain and an obvious excess of ammonia should be passed into the mixture. 

It is frequently necessary to dissolve a precipitate completely. This is most readily done by pouring the solvent, preferably whilst hot, on to the filter and repeating the process, if necessary, until all the precipitate has passed into solution. If it is desired to maintain a small volume of the liquid, the filtrate may be poured repeatedly through the filter until all the precipitate has passed into solution. When only a small quantity of the precipitate is available, the filter paper and precipitate may be heated with the solvent and filtered. 

Like the C-terminal amide moiety, the presence of a sulfate group is required for sulfakinin myotropic activity. Nevertheless, as the active CCK analogs attest, the position of the sulfate is less critical (15). With the apparent flexibility of sulfakinin activity in relation to movement of sulfate position in the sequence, it was of interest to determine the limits of sulfate mobility without precipitating complete loss of activity. A series... 

A solution of uranyl acetate (5 g.) in 50 ml. of glacial acetic acid is heated at reflux, with stirring, with amalgamated zinc. On completion of the reduction, the slurry of Zn[U(OOCCH3)6] in acetic acid is separated from the amalgamated zinc by decantation. The complex is precipitated completely by refluxing the decantate with an excess of acetic anhydride (20 ml.). The solid is filtered on a sintered-glass crucible and washed twice with ether. 

Gravimetric Methods.—When the chromium is in solution as a chromic salt, it can be precipitated completely from the boiling solution by the addition of ammonium hydroxide in the presence of ammonium salts. The precipitate may be dried at 100° C. and converted by gentle ignition to the dark green sesquioxide and weighed as such. Ammonium sulphide or hydrazine sulphate may also be used as the precipitant. 

The reaction was done in a mixture of ethanol and water (VA 2/5) at the same temperature as that above. The precumor (pure enantiomers or racemic) was first dissolved in ethanol, and on addition of water a white precipitate appeared. An aqueous NaOH solution was thai added until pH 12 was attained, and the mixture was heated in an oil bath at 80 °C for 6 days. In the case of the racemic mixture, the precipitate completely dissolved after 10 min, and the formation of a white precipitate was observed after 0.5 h. This dissolution was never observed for the pure enantiomers, the reaction occurring in a heterogeneous solid/liquid state. Usual woi4c-up (washing with water until neutral pH and drying at 110 °C) resulted in white powders in all cases. The features obtained fiom die SEM images of the enantiopure-derived materials were completely different fiom those of the racemic material (Fig. 2). 

After completion of the reaction and removal of phosgene excess, HMGCI.HCI which precipitates completely is filtrated thus giving very pure product (Ref. 10). 

Metastatic spread of a tumour to an important site may precipitate complete system failure. For example, destruction of the adrenal cortex by tumour causes impaired aldosterone and cortisol secretion. with potentially fatal con.scqucnces. 

Brown, deliquesc crystals. Sol in water with turbidity with much water a brown basic salt precipitates completely sol in dtl HNOj Keep wen closed, protected from light. 

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