Sodium chloride freezing point

Freezing point of sodium chloride brines Compiled in collaboration with C. D. Looker, Ph.D., International Salt Co., Inc. 

Sodium chloride, an ordinaiy salt (NaCT), is the least expensive per volume of any brine available. It can be used in contact with food and in open systems because of its low toxicity. Heat transfer coefficients are relatively high. However, its drawbacks are it has a relatively high freezing point and is highly corrosive (requires inhibitors thus must Be checked on a regular schedule). 

The freezing points of electrolyte solutions, like their vapor pressures, are lower than those of nonelectrolytes at the same concentration. Sodium chloride and calcium chloride are used to lower the melting point of ice on highways their aqueous solutions can have freezing points as low as —21 and — 55°C, respectively. 

In an electrolyte solution, each formula unit contributes two or more ions. Sodium chloride, for instance, dissolves to give Na+ and Cl ions, and both kinds of ions contribute to the depression of the freezing point. The cations and anions contribute nearly independently in very dilute solutions, and so the total solute molality is twice the molality of NaCl formula units. In place of Eq. 5a we write... 

Sodium ehloride equivalent, whieh is produced by dividing the value for the depression of freezing-point produced by a solution of the substance by the corresponding value of a solution of sodium chloride of the same strength. 

Antifreezing agents for cement consist mainly of salts such as calcium chloride, magnesium chloride, sodium chloride, and soda. Calcium chloride is highly corrosive and very restricted in use. Some salts, especially potassium chloride, will affect the curing time of cement. The latter chemical is in fact used to increase the pot life of cement. Likewise, alcohol freezing-point depressants, such as ethylene glycol, can be also included in the composition [1022]. 

We must appreciate, however, that no chemical reaction occurs between the salt and the water more or less, any ionic salt, when put on ice, will therefore cause it to melt. The chemical identity of the salt is irrelevant - it need not be sodium chloride at all. What matters is the amount of the salt added to the ice, which relates eventually to the mole fraction of salt. So, what is the magnitude of the freezing-point depression ... 

TABLE 8.2. Sodium Chloride Equivalents (E) and Freezing Point Depression (ATI" ") Values of Selected Compounds. 

Step 3 Since 0.9% sodium chloride has a freezing point depression of 0.52, one can calculate the percentage concentration of sodium chloride required to lower the difference in freezing points, i.e., the value obtained in Step 2, ATf, by the method of proportion. The calculations involved in this method are explained best by following examples. 

Step 2 Find A7 by subtracting the AT value of 1% atropine sulfate from the AT of blood plasma, i.e., 0.52 - 0.07 = 0.45. This means, sufficient sodium chloride must be added to lower the freezing point by an additional 0.45°. 

In Table 8.2, it is observed that 1% solution of sodium chloride has a freezing point lowering of 0.58. Therefore, one can also express the proportion as ... 

Hellmuth believes that the polymeric material forms. If magnesium acetate is simply the internally chelated material, then it should be quickly washed away. The combination of calcium and magnesium acetates is known as CMA. CMA is more expensive than sodium chloride or calcium chloride, but it does not damage plant life and it has a much longer effective life. The polymer seeks the cracks and crevices in and around the pavement and remains until needed again to lower the freezing point of water. Often, one application of CMA is sufficient for a winter season. 

Several attempts have been made to use other materials as antifreezes. Salts, such as calcium chloride or sodium acetate, depress freezing points, but are corrosive. They can cause severe corrosive damage to the engine. Leakage of these salt solutions can cause short circuiting of the electrical system. 

Each kilogram of seawater contains roughly 35 g of dissolved salts. Assuming that all these salts are sodium chloride, what is the freezing point of seawater ... 

The filtrate, obtained after the crystals of bis-(4-iminopentane-2-ono) copper (II) were filtered off, was evaporated under reduced pressure. The residue was extracted with water, the extracts were filtered, and the filtrate was treated with sodium hydroxide and p-toluenesulfonyl chloride (18). In this way, about 30% of the 1,3-propanediamine was accounted for as the crude ditosylate (identity confirmed by lack of freezing-point depression with authentic sample), but only a trace of diamine could be detected in the distillate. 

Plot the change in the saturated vapour pressure of water over pure water and an aqueous solution of sugar (sodium chloride) against the temperature. How does the freezing (boiling) point of water change when it contains solutes (sugar, sodium chloride) Define the cryoscopic and ebullioscopic constants of water. What is their numerical value State Raoult s laws and write their mathematical expression. How can the molecular masses of solids be determined ... 

Put one test tube with bromine into a beaker with a cooling mixture (ice and sodium chloride) whose temperature should not exceed —10 °C. What is the freezing point of bromine ... 

Mussenden, S., Hodges, J. and Hiley, P. G. 1977. Sodium and chloride in cows drinking water and freezing point of milk. J. Dairy Sci. 60, 1554-1558. 

Prentice, J. H. 1978. Freezing point data on aqueous solutions of sucrose and sodium chloride and the Hortvet test A reappraisal. Analyst 103, 1269-1273. 

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