What is an Ice Point?

The freezing point foreign name ice point refers to the freezing point of water, that is, the temperature at which water changes from liquid to solid. At standard atmospheric pressure, the temperature is 0 ° C. The standard temperature is related to water impurities, but water with impurities cannot be regarded as the standard freezing point.

Freezing point and

Freezing Calibration Thermometer

Freezing point can be used to calibrate thermometer readings. Because the freezing point is constant at a given pressure, the readings of a precision thermometer can be calibrated based on the temperature of the ice-water mixture at that pressure. Many instrument companies have developed instruments for calibrating thermometers based on this principle-the freezing point reference chamber ^[1-2] . The freezing point reference chamber usually uses a freezing point at standard atmospheric pressure, which is 0 ° C, to calibrate the readings of precision thermometers.

Freezing point data method

We can know the concentration of dissolved matter in the aqueous solution by the freezing point of the aqueous solution. When water contains dissolved matter, the freezing point will decrease. The higher the dissolved matter concentration, the lower the freezing point. By formula

Calculate the freezing point or dissolved matter concentration of the aqueous solution ^[3] : in the formula

Is the difference between the freezing point (0 ° C) of pure water and the freezing point of the solution at standard atmospheric pressure, K is the constant of the molar freezing point reduction of water (its value is 1.86 K · Kg / mol), and b is the mass molar concentration of the dissolved matter.

In the use of pharmaceutical injections, the injection must be close to the osmotic value of the serum (usually about 285 mosm / kg) in order to reduce the discomfort during injection. The freezing point reduction data method is a commonly used osmotic pressure adjustment method. Generally, the freezing point of plasma is -0.52 ° C. When the freezing point of the aqueous solution is lowered to -0.52 , it is isotonic with plasma. The amount of isotonicity regulator can be directly calculated using the formula W = (0.52-a) / b (this formula is based on the above formula

Evolved). Among them, W is the percentage of the isotonicity regulator to be added to prepare an isotonic solution, a is the freezing point of the drug solution, and b is the freezing point of the 1% solution of the isotonicity agent. By calculating the amount of isotonicity regulator, an injection that is isotonic with plasma can be formulated. This is the freezing point reduction data method.