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The osmol gap is typically calculated with the following formula (all values in mmol/L): = = ([+] + [] + []) In non-SI laboratory units: Calculated osmolality = 2 x [Na mmol/L] + [glucose mg/dL] / 18 + [BUN mg/dL] / 2.8 + [ethanol/3.7] [3] (note: the values 18 and 2.8 convert mg/dL into mmol/L; the molecular weight of ethanol is 46, but empiric data shows that it does not act as an ideal ...
Measured osmolality is abbreviated "MO", calculated osmolarity is abbreviated "CO", and the osmolality gap is abbreviated "OG". [9] Clinically, the osmolar gap is used to detect the presence of an osmotically active particle that is not normally found in plasma, usually a toxic alcohol such as ethanol, methanol or isopropyl alcohol.
Both sodium and chloride ions affect the osmotic pressure of the solution. [2] [Note: NaCl does not dissociate completely in water at standard temperature and pressure, so the solution will be composed of Na+ ions, Cl- ions, and some NaCl molecules, with actual osmolality = Na+ concentration x 1.75]
How rapidly the kidney clears the blood plasma of a substance (be it water or solute) is the renal clearance, which is related to the rate of urine production. The rate at which plasma is cleared of solute is the osmolal clearance; the rate at which plasma is cleared of solute-free water is the free water clearance.
Stool osmotic gap is a measurement of the difference in solute types between serum and feces, used to distinguish among different causes of diarrhea. Feces is normally in osmotic equilibrium with blood serum, which the human body maintains between 290–300 mOsm/kg. [ 1 ]
Osmotic pressure is the minimum pressure which needs to be applied to a solution to prevent the inward flow of its pure solvent across a semipermeable membrane. [1] It is also defined as the measure of the tendency of a solution to take in its pure solvent by osmosis .
For instance, for solutions of magnesium chloride, the vapor pressure is slightly greater than that predicted by Raoult's law up to a concentration of 0.7 mol/kg, after which the vapor pressure is lower than Raoult's law predicts. For aqueous solutions, the osmotic coefficients can be calculated theoretically by Pitzer equations [4] or TCPC model.
They can be used to calculate mixed ion activity coefficients and water activities in solutions of high ionic strength for which the Debye–Hückel theory is no longer adequate. They are more rigorous than the equations of specific ion interaction theory (SIT theory), but Pitzer parameters are more difficult to determine experimentally than ...