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.
It's called osmosis.   A selectively permeable membrane will only allow certain molecules  to pass trough. To illustrate: If you have a high concentration of  sugar mole â¦ cules on one side of the membrane, no sugar on the other  side, and the sugar molecules are too big to pass trough the  membrane. If this is the case, then water molecules will diffuse  over to the side of the membrane with a high sugar concentration.  This happens because the molecules try to distribute themselves  evenly in the solution. The water molecules move because the sugar  molecules can't. 3 people found this useful.