Calcium Chloride solutions in the operation of precipitation gages

Freezing test indicate that Calcium Chloride solution is superior to NaCl solution in precipitation gages. The brine is used to melt the snow as it falls into the gage and to prevent damage to the gage by freezing water. A eutectic freezing point of -60deg F results with a solution of about 30% Calcium Chloride by weight. A 23% NaCl solution forms salt crystals at -5deg F and becomes solid at -8deg F. Precipitation gages in which Calcium Chloride is used are usually charged with a 33.4% solution (1 qt. of salt to 1 qt. of water and 4 oz. SAE.10) after 2.5 in. of precipitation has been caught, another quart of salt is added to strengthen the solution. The film of oil prevents evaporation and overcomes the deliquescent effect of the salt. Tests were made of various percentages of strength solutions in a dry-ice chamber. NaCl solutions and a sample of water from the Great Salt Lake turned solid at -8deg F. However, the 33.4% solution of Calcium Chloride began to become slushy like frazil ice at -55de gF, and remained in this semi-liquid solution for two hours at -65deg F. Thus assuring no damage to the gages.