Two different products of calcium magnesium acetate (CMA) were tested. Their molar ratios, Ca/Mg, were 1.26 and 0.91 respectively. Both products were used as concentrated solutions. In addition, the 0.91 product was also used in a solution, which was diluted so that its freezing point depression was as great as that of a 3 percent (by mass) sodium chloride solution. - Prisms of 0.60 mortar expanded more in a concentrated solution of 1.26 CMA than in one of 0.91 CMA. - The loss of mass in mortar prisms on immersion in concentrated solutions was more rapid in 0.91 CMA than in 1.26 CMA, and much more rapid at +20 than at +5°C. Immersion in the dilute CMA caused an increase of the mass during the first six months. - With respect to the flexural and compressive strength, the dilute solution of 0.91 CMA caused the greatest decreases. However, in several cases the compressive strength after immersion in concentrated solution could not be determined.