Chloride Content by Weight of Concrete. Q.: For corrosion protection, ACI 318-95, Building Code Requirements for Structural Concrete, specifies maximum water-soluble chloride ion in concrete as percent by weight of cement. What are acceptable levels when measuring chloride-ion content in existing concreteâspecifically, by weight of the concrete sample?
Plasma membranes are selectively permeable, regulating the cellâs molecular traffic. Hydrophobic (nonpolar) molecules, such as hydrocarbons, can dissolve in the lipid bilayer and. pass through the membrane rapidly. Polar molecules, such as sugars, do not cross the membrane easily. Transport Membranes Transport proteins allow passage of hydrophilic substances across the membrane.
permeable to polar molecules and ions, which is discussed below.) All in all, relatively few kinds of endogenous molecules cross membranes by lipid diffusion. However, most drugs are small amphipathic compounds, and therefore rely. heavily on lipid diffusion to move through different compartments in the body. The ability of drugs to diffuse across membranes is heavily inï¬uenced by the. ionizability of the drug in the surrounding medium. The pH of body compartments inï¬uences lipid diffusion of drugs.