Visking membrane

The use of membranes for separating particles of colloidal dimensions is termed dialysis. The most commonly used membranes are prepared from regenerated cellulose products such as collodion (a partially evaporated solution of cellulose nitrate in alcohol plus ether), Cellophane and Visking. Membranes with various, approximately known, pore sizes can be obtained commercially (usually in the form of sausage skins or thimbles ). However, particle size and pore size cannot be properly correlated, since the permeability of a membrane is also affected by factors such as electrical repulsion when. the membrane and particles are of like charge, and particle adsorption on the filter which can lead to a blocking of the pores. 

The transport cell devised by Nogami and coworkers consists of three compartments partitioned with two semipermeable (Visking) membranes, the central compartment being thin and containing a solution of polyvinylpyrrolidone, which... 

The electrophoretic mobility in acetate buffo , pH 5.0, and in veronal buffer, pH 8.6, was observed to be —15.8, and —i8.6-io cm /sec volt respectively. The molecular weight is small, since the substance dialyzed slowly through Visking membranes values between 1240 and 2075 have been observed for especially low molecular weight, highly polydisperse samples, isolated from patients with Hurler s S3mdrome . ... 

The permeability tests for alkali metal ions in the aqueous solution were also conducted. When an aqueous salt solution moves to cell 2 through the membrane from cell 1, the apparent diffusion coefficient of the salt D can be deduced from a relationship among the cell volumes Vj and V2, the solution concentration cx and c2, the thickness of membrane, and time t6 . In Table 12, permeabilities of potassium chloride and sodium chloride through the 67 membrane prepared by the casting polymerization technique from the monomer solution in THF or DMSO are compared with each other and with that the permeability through Visking dialyzer tubing. The... 

Ratio of apparent diffusion coefficient of 67 membrane to the cellulosic membrane. Visking dialyzer tubing. 

One of the problems which existed when this study began was that of suitable membranes. Regenerated cellulose membranes [Visking Co., Chicago, 111.] having an effective pore diameter of 24 A were easily available in both sheet and tube form. The problem with such material is the rate of decomposition. It was at first assumed that a run could be made before the membrane was decomposed. However, this objective proved to be impossible to attain. Usually in about 6 to 10 days the membrane would fail. 

One practical application of osmosis is the process of dialysis in which colloidal dispersions are purified by removing from them traces of reagents or by-products remaining from, or produced in, their preparation. The colloid is contained in a bag of semi-permeable material, e.g. a Visking (cellulose) membrane. This is immersed in a bath of distilled water, which is replaced from time to time. The unwanted components, to which the membrane is permeable, diffuse out of the dialysis bag, and completion of the... 

Into each of the two identical compartments (each 7 ml capacity) of a dialysis cell is charged 5 ml of reaction mixture—the Cr-labeled chrom-ium(III) in the back, the unlabeled chromium(III) in the front. The membrane separating the compartments is Visking, a regenerated cellulose whose average pore diameter is 4.8 mfi its diameter is 38 mm. 

UV-VIS extinction spectra were measitred with a Lambda 35 spectrophotometer (Perkin Elmer, USA). Particle size distribution, based on hydrodynamic diameter, was evaluated by Nano S (Malvern, UK), a dynamic light scattering analyzer (DLS). Urueacted metal cations, extracted from the sample by a semi-permeable osmotic membrane (Visking tube), were detected by ICP-AES qirantitative analysis (Liberty 200, Varian, Austraha) in order to determine the reaction yield. Suspensiorts were dropped and dried on a copper grid, then observed by high resolution transmission electron microscopy (HRTEM) (Tecnai F20) and by the STEM mode with microanalysis EDX. 

---