Volume in Dissolution

Change in Volume in[Dissolution. Dissolution of Sodium[Chlo-ride in Water. Weigh 21 g of sodium chloride. Calculate the volume occupied by the given amount of salt using a table of the density of substances (see Appendix 1, Table 4). Pour 90 ml of water into a 

100-ml measuring cylinder, and introduce a glass rod and a thermometer into it. Note the level of the water in the cylinder and its temperature. Carefully pour in the weighed salt using a dry funnel so that the salt does not get onto the walls of the cylinder. By stirring with the rod, achieve complete dissolution of the salt. When the-solution acquires room temperature, note its volume. 

Dissolution of Ammonium Chloride in Water. Weigh 21 g of ammonium chloride, calculate its volume, and dissolve it in 150 ml of water, proceeding in the same way as in the preceding experiment. Note the volume of the solution obtained. 

Dissolution of Sugar in Water. Take 50 g of sugar and dissolve it in 250 ml of water. Measure the volume of the solution. 

Dissolution of Ethanol in Water. Pour 4 ml of water into a 10-mI measuring cylinder. Put a thin glass rod into it and note the level of the liquid in the cylinder. Add 4 ml of water and again note the level. Pour out the water. Again pour 4 ml of water and 4 ml of absolute ethanol into the cylinder and thoroughly mix the liquid with the rod. What is observed Enter the data of all the experiments iu your laboratory notebook using Form 12. 

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Drugs in Class II have low aqueous solubility (but high membrane permeability), and any factor affecting dissolution rate would be expected to have an impact on the absorption of such compounds. Factors that are noted in Fig. 11, such as fluid pH, volume and viscosity, and bile secretion (especially in response to fatty foods), might be expected to play a role in dissolution rate and thereby affect absorption. Compounds that fall into this class include carbamazepine, cyclosporin, digoxin, griseofulvin, and spironolactone. Food would be expected to exert a potentially significant affect on... 

Since mercury has a contact angle with most solids of about 140°, it follows that its cosine is negative (i.e., it takes applied pressure to introduce mercury into a pore). In a mercury porosimeter, a solids sample is evacuated in a cell, mercury is then intruded, and the volume, V, is noted (it actually reads out), and the pressure, P, is then increased stepwise. In this fashion it is possible to deduce the pore volume of a particular radius [corresponding to P by Eq. (21)]. A pore size distribution will give the total internal pore area as well, which can be of importance in dissolution. 

A sphere is assumed to be a poorly soluble solute particle and therefore to have a constant radius rQ. However, the solid solute quickly dissolves, so the concentration on the surface of the sphere is equal to its solubility. Also, we assume we have a large volume of dissolution medium so that the bulk concentration is very low compared to the solubility (sink condition). The diffusion equation for a constant diffusion coefficient in a spherical coordinate system is... 

While batch dissolution methods are simple to set up and to operate, are widely used, and may be carefully and reproducibly standardized, they suffer from the following disadvantages (1) the hydrodynamics are usually poorly characterized, with the notable exception of the rotating disc method, (2) a small change in dissolution rate will often create an undetectable and therefore an immeasurable perturbation in the dissolution time curve, and (3) the solute concentration cb may not be uniform throughout the solution volume V. 

Dissolve 1.000 g Sb in (1) 10 ml HN03 plus 5 ml HC1, and dilute to volume when dissolution is complete or (2) 18 ml HBr plus 2 ml liquid Br2 when dissolution is complete add 10 ml HC104, heat in a well-ventilated hood while swirling until white fumes appear and continue for several minutes to expel all HBr, then cool and dilute to volume. 

As shown in Table 2, the recommended volume of dissolution medium is 500-1000 mL, with 900 mL as the most common volume when using the basket or paddle apparatus. The volume can be raised to between 2 and 4L, depending on the concentration and sink conditions of the drug, but proper justification is expected. 

Accuracy samples are prepared by spiking bulk drug and excipients in the specified volume of dissolution fluid. The concentration ranges of the bulk drug spikes are the same... 

For comparison, a telechelic sulfonated polystyrene with a functionality f = 1.95 was prepared. In cyclohexane the material forms a gel independent of the concentration. At high concentrations the sample swells. When lower concentrations were prepared, separation to a gel and sol phase was observed. Thus, dilution in cyclohexane does not result in dissolution of the gel even at elevated temperatures. Given the high equilibrium constant determined for the association of the mono functional sample, the amount of polymer in the sol phase can be neglected. Hence, the volume fraction of polymer in the gel phase can be calculated from the volume ratio of the sol and gel phases and the total polymer concentration. The plot in Figure 9 shows that the polymer volume fraction in the gel is constant over a wide range of concentrations. 

The effects of various formulation factors on the in vitro release characteristics of spherical polymethylmethacrylate implants were studied. Physical and mathematical models were proposed to describe the in vitro release profiles. The in vitro release data could be described by a biexponential equation of the following type fraction of tobramycin remaining in the implant at time t=Aerai+BQ, where a, and P represent the rate constants for the initial rapid and subsequent slow phases of release. The influence of drug loading, volume of dissolution medium, implant size and type of cement and the incorporation of water-soluble additives on the release profiles and a and P rate constants is described. 

Volume Displacement. This parameter is not a factor in dissolution testing but can prove to be a very important factor in automated assay, content uniformity, or degradation and impurities testing. It specifically addresses the volume displaced by the tablets in solution. Since manual sample preparations are often prepared utilizing volumetric flasks where the solution is diluted to the mark, the actual volume of solvent added to the flask is irrelevant. However, this actual volume... 

Synthesis of the complex. In a 50-mL Schlenk flask, N,N-bis(2-mercapto-ethyl)2-methylthioethylamine (0.1 g, 0.47 mmole) is dissolved in methanol (10 mL) and subsequently cooled to 5°C in an ice bath. To the cooled solution, a solution of anhydrous nickel acetate (84 mg, 0.47 mmole) in methanol (10 mL) is added dropwise with rapid stirring. The product, a red-black, microcrystalline solid, forms immediately and is collected by filtration, washed several times with small amounts of methanol, and dried in vacuo. Yield = 160 mg (65%). The product obtained from purified ligand is pure by elemental analysis. If crude ligand is used, the complex may be purified by recrystallization from CH2C12 (minimum volume for dissolution) upon addition of petroleum ether or hexane (five times the volume of CH2C12 used). 

There are also special cells for use with USP Apparatus 4 in a closed-loop configuration. Using a 100 mL bottle, a total volume of dissolution media ranges from 25 to 100 mL. For very low volume assembly, a test tube with a rubber stopper allowing for inlet and outlet tubing can be used. However, with the need for even smaller volumes, internal modifications should be made to the apparatus to minimize the impact on functionality due to a change in the internal tubing volumes. Also, the additional volume of the flow cell must be considered. For example, the implant... 

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